Macro Neuro Anatomy
The nervous system is the complex network of nerves and cells that convey information to and from the brain and spinal cord to all other parts of the body. The nervous system is divided into subsystems that work together to control our physiological and psychological processes and our voluntary and involuntary actions. It includes the central nervous system, made up of the brain and spinal cord, and the peripheral nervous system, made up of all other nerves and ganglia outside the brain and spinal cord.
Central Nervous System:
The central nervous system (CNS) is a division of the nervous system that consists of the brain and the spinal cord. The CNS receives and processes information arising from the whole body, and integrates it such as to coordinate all bodily functions and mental processes. The CNS is essential to our survival and is therefore physically protected by the skull and spine, and chemically protected by the blood-brain barrier.
Peripheral Nervous System:
The peripheral nervous system (PNS) is a division of the nervous system that consists of all the nerves and ganglia located outside the brain and spinal cord. The main function of the PNS is to serve as a communication device between the CNS and the rest of the body. It collects information from other organs and systems and from the environment, and conveys it to the brain and spinal cord. It also executes and transmits orders arising from the CNS to all other organs and systems, including motor control. It is subdivided into the somatic, the autonomic and the enteric nervous systems.
Somatic Nervous System:
The somatic nervous system is a subdivision of the peripheral nervous system responsible for the reception of sensory information and for the voluntary control of body movements. It consists of afferent nerves, which transmit sensory information into the CNS, and of efferent nerves, which transmit motor commands from the CNS to the skeletal muscles.
Autonomic Nervous System:
The autonomic nervous system is a subdivision of the peripheral nervous system that controls our internal organs and our unconscious bodily functions, such as breathing, heartbeat, blood flow, and digestion, for example. It is further divided into two branches: the sympathetic and the parasympathetic nervous systems.
Sympathetic Nervous System:
The sympathetic nervous system is one of the two subdivisions of the autonomic nervous system. It surveys and acts on our body such as to maintain its balance (homeostasis). It is also responsible for the body’s “fight-or-flight” response, the physiological unconscious reactions to potentially harmful events or threats to survival, including cardiac and respiratory rates, for example. Noradrenaline is its main neurotransmitter.
Parasympathetic Nervous System:
The parasympathetic nervous system is one of the two subdivisions of the autonomic nervous system. It is responsible for the body’s unconscious actions associated with “rest-and-digest” or “feed-and-breed” functions, such as digestion, urination, defecation, or sexual arousal, for example. Acetylcholine is its main neurotransmitter.
Enteric Nervous System:
The enteric nervous system is a subdivision of the peripheral nervous system that is embedded in the walls of the gastrointestinal tract and controls the gastrointestinal system. The enteric nervous system is highly complex, containing sensory neurons that determine the mechanical and chemical status of the gastrointestinal tract, and motor neurons that control its peristaltic movements. Even though it is connected to the central nervous system through the autonomic nervous system, it can act autonomously through its reflex activity.
A nerve is a bundle of axons (or nerve fibers) and support cells wrapped in connective tissue. Nerves convey sensory information to the central nervous system through afferent nerve fibers, and transmit motor commands to muscles and glands through efferent nerve fibers. Nerves are part of the peripheral nervous system.
Sensory nerves transmit sensory information from the skin, muscles, and internal organs to the central nervous system. They are also known as afferent nerves and are part of the peripheral nervous system.
Motor nerves are nerves that convey signals from the central nervous system to muscles and internal organs. They are also known as efferent nerves and are part of the peripheral nervous system.
The Vagus nerve is the longest and most complex cranial nerve. It is closely associated with stress and anxiety responses. 80-90% of its nerve fibers are sensory nerve fibers that communicate the state of the viscera to the brain. It also provides parasympathetic innervation to the heart, lungs and gastrointestinal tract, among others, and can therefore control respiratory and heart rates, blood pressure, and digestion. It is the major communication route between the central and the enteric nervous system.
Grey matter is a component of the central nervous system that consists of neuronal cell bodies, dendrites, unmyelinated axons, glial cells, synapses, and capillaries. It is distinguished from white matter by having a higher density of cell bodies, as opposed to the higher density of axons found in white matter. It is found in the outer layer of the brain (the cerebral cortex) and of the cerebellum (cerebellar cortex), as well as in some deeper structures of the brain and cerebellum, in the brainstem, and in the spinal cord. Grey matter is associated with information processing and cognition, being essential for a number of functions, including motor control, sensory perception, memory, language, emotions, and decision making.
White matter is a component of the central nervous system that consists mainly of glial cells and myelinated axons, having a low density of neuronal cell bodies. White matter is responsible for the transmission of information between different regions of the central nervous system. By coordinating this communication between different brain regions, white matter can affect how the brain functions.
Blood Brain Barrier:
The blood-brain barrier is a highly selective permeability barrier that separates the blood from the extracellular fluid of the central nervous system (cerebrospinal fluid). The blood-brain barrier is a defense system for the brain – it allows substances that are crucial to the CNS to pass while restricting access to bacteria, neurotoxins and other harmful substances. It is formed along the smaller blood vessels, the capillaries, with the aid of astrocytes, a type of glial cell found in the CNS.
Cerebrospinal fluid (CSF) is a fluid found in the brain and spinal cord. It provides buoyancy to the brain, and physical and chemical protection to the central nervous system. CSF is produced from blood plasma by a cluster of cells called choroid plexus that are found in each of the brain’s cavities, the ventricles. It fills the ventricles and the subarachnoid space that covers the brain and spinal cord.
The spinal cord is one of the organs of the central nervous system, along with the brain. It is a tubular structure that starts in the brainstem and extends within the vertebral column. Its major functions are to conduct motor information from the brain to the peripheral nervous system and sensory information from the periphery to the brain.
Gut Brain Axis:
The gut-brain axis refers to the communication system between the gastrointestinal tract and the brain. It allows the bacteria in the gut (the gut microbiota) to communicate with the central nervous system. The gut-brain axis uses neuronal, endocrine and immune pathways to convey information between the gut microbiota and the brain, thereby keeping the brain informed on the status of the intestinal flora, which is crucial to health, and allowing the brain to act on it when needed. It also provides a pathway through which that gut microbiota can influence brain functions, including mood, anxiety, and even cognitive functions.
The brain is the main organ of the nervous system. It is the most complex organ in the human body, being made up of around 86 billion neurons and 150 trillion synapses. The brain controls all other organs and systems, and the body’s physiological and psychological processes.
The lobes of the brain are anatomical divisions of the brain, more specifically, of the cerebrum, containing the cerebral cortex. There are four major lobes: frontal, temporal, occipital and parietal, and they are found in both cerebral hemispheres. They participate in different brain functions.
The frontal lobe is located at the frontal upper area of the brain, in both cerebral hemispheres. The frontal lobe executes higher mental processes such as conscious thinking, decision making, planning, and problem solving, and it’s where personality is based. It also contains the primary motor cortex, playing a large role in the control of voluntary movement. The frontal lobe also regulates mood and emotions, social, emotional, and sexual behavior, and contributes to the retention of long term emotional memories.
The temporal lobe is located at the bottom lateral part of the brain, in both cerebral hemispheres. The temporal lobe receives, processes and makes sense of auditory information such as sounds and speech, allowing us to understand language. It also interprets the meaning of visual stimuli, allowing us to recognize objects. The temporal lobe also contains structures associated with long-term memory of facts and events.
The occipital lobe is located at the lower back part of the brain, in both cerebral hemispheres. The occipital lobe contains most of the visual cortex, and therefore receives, processes and makes sense of visual information.
The parietal lobe is located at the upper back part of the brain, in both cerebral hemispheres. The parietal lobe integrates and assists in the processing of sensory information. It contains the somatosensory cortex, being the main responsible for processing touch, pain, temperature and proprioception, as well as spatial awareness and navigation. Some areas of the parietal lobe also contribute to language processing.
The brain is divided in half by a longitudinal fissure, originating two anatomical divisions – the cerebral hemispheres (left and right hemispheres). Anatomically, the hemispheres are roughly mirror images of one another. At the cellular levels, the two hemispheres have extensive differences in the type of cells and molecules that predominate in certain areas, as well as in the predominant functions. The hemispheres are connected by the corpus callosum.
The left side of the brain, or left hemisphere, is responsible for the motor control of the right side of the body, and is the more logical side of the brain. The left hemisphere performs some specific mathematical tasks such as exact calculation, numerical comparison, and estimation. It also contains the major language areas, Broca’s area and Wernicke’s area, controlling functions of language that relate to a literal use, such as grammar and vocabulary. The left hemisphere is also responsible for fact retrieval.
The right side of the brain, or right hemisphere, is responsible for the motor control of the left side of the body, and performs tasks that have to do with creativity and arts. The left hemisphere is responsible for more subjective functions of language, such as intonation and emphasis. It also performs less exact mathematical tasks such as approximate calculation, numerical comparison, and estimation.
The corpus callosum is a white matter structure that connects the two cerebral hemispheres. It is a wide and flat cluster of nerve fibers located beneath the cerebral cortex. The corpus callosum allows the communication between the two hemispheres of the brain, transmitting information from one side to the other.
The brainstem is the lower posterior part of the brain, contiguous with the spinal cord. It includes three different zones: the medulla oblongata, the pons, and the midbrain. As a whole, the brainstem supplies most of the motor and sensory innervation of the face and neck through the cranial nerves. Motor and sensory information from the rest of the body, specifically touch, pain, and temperature, also pass through the brainstem. It also has an important role in regulating autonomic functions, namely heart rate and breathing. It has a key role in maintaining consciousness, and in regulating sleep and feeding.
The medulla oblongata is the lower part of the brain stem, adjacent to the spinal cord. The medulla regulates some vital involuntary functions such as breathing, heart rate, and blood pressure. It also transfers information between the brain and the spinal cord.
The pons (from the Latin word for bridge) is a relay station of the brain stem. It is essential for the transmission of messages from the cerebral cortex to the cerebellum and medulla, and for the transmission of sensory information from the spinal cord to the thalamus. It is the area where REM sleep originates, and it therefore has a key role in sleep and dreaming.
The midbrain is a part of the brain stem located between the pons and the cerebral cortex. The midbrain participates in a number of functions, including vision, hearing, motor control, temperature regulation, alertness, and sleep/wake cycle regulation.
The reticular formation is a group of small brain structures (nuclei) dispersed throughout the brainstem. The reticular formation has a key role in maintaining wakefulness and consciousness. The reticular formation contains the area where most of the brain’s serotonin is produced, the Raphe nuclei, therefore playing an important role in mood regulation. It is also involved in motor coordination.
The basal ganglia are a group of structures, or nuclei, located below the cerebral cortex, in the brain. These include the caudate nucleus, the nucleus accumbens, and the substantia nigra, among others. The basal ganglia nuclei are strongly connected with the cerebral cortex, the thalamus, and the brainstem, and therefore participate in a multitude of functions. The basal ganglia are associated with action selection, i.e. the decision of which behaviors to carry out at any given time. They are also associated with voluntary motor control, eye movements, learning, emotions, motivation, and habits.
The caudate nucleus is one of the structures of the basal ganglia, having an important role in the communication between these and the cerebral cortex. The caudate nucleus participates in the regulation of learning, memory, sleep, social behavior, and voluntary movement.
The nucleus accumbens is one of the structures of the basal ganglia. The nucleus accumbens plays a major role in addiction. It is part of the reward system, having important functions in processing reward and in reinforcement learning. It also has significant roles in aversion, motivation, and pleasure.
The substantia nigra is one of the structures of the basal ganglia. It acts as a processing center, and conveys processed signals to the thalamus. The substantia nigra plays an important role in motor control, including eye movement and the planning of motor actions. It also participates in the regulation of reward, pleasure, and addictive behavior. It is involved in learned responses to stimuli and in the regulation of the sleep-wake cycle. The substantia nigra is widely recognized for its role in Parkinson’s disease, namely through the loss of dopaminergic neurons in this area.
Specific Brain Structures:
Specific functional regions of the brain associated with particular physiologic, cognitive, and psycho-emotional functions.
The cerebellum is a region of the brain that appears as a separate structure at the lower extremity of the brain. Its main function is fine motor control. It receives and integrates sensory information from the spinal cord and other parts of the brain, and processes it such as to perfect the timing, coordination, and precision of movements. The cerebellum is also involved in some cognitive functions such as attention, language, and fear and pleasure responses.
The cerebral cortex is the brain’s outer layer of neuronal tissue. It is organized in folds and grooves that greatly increase its surface area. The cortex is mostly composed of neuronal cell bodies, glial cells and capillaries (grey matter). It is divided into two hemispheres (left and right) and into lobes (frontal, parietal, temporal and occipital). It contains sensory, motor, and association areas, the latter allowing perception, abstract thinking and language. The cerebral cortex integrates information from other brain areas and is essential for memory, attention, and consciousness.
The neocortex is the outermost region of the cerebral cortex, consisting of grey matter. It has a key role in higher cognitive functions such as conscious thought, language and spatial reasoning, as well as in sensory perception and generation of motor commands.
The sensory cortices are the areas of the cerebral cortex involved in processing information from the senses, i.e., vision, audition, olfaction, taste, and touch. They also process information regarding the sense of one’s body, balance, temperature, and pain.
The prefrontal cortex is the part of the cerebral cortex that covers the frontal lobe of the brain. The prefrontal cortex is involved in executive function; it organizes thoughts and actions such as to allow complex behaviors, goal-oriented behavior, social behavior, rule learning, decision making, and prediction of outcomes. The prefrontal cortex is regarded as the source of one’s personality.
The limbic brain (or limbic system) is a cluster of brain structures mainly involved in emotional processes. The limbic system also participates in a number of functions such as behavior, motivation, reward, decision-making, long-term memory, and learning. It also contributes to the regulation of autonomic processes.
The amygdala is an almond shaped structure located in each of the temporal lobes of the brain. It is part of the limbic system. The amygdala is connected to a number of brain structures, namely the hippocampus, which is also part of the limbic system. As such, the amygdala is involved in emotion, motivation, learning, and long-term memory. It has a key role in memory consolidation, decision-making, and emotional reactions. By participating in the formation and storage of memories associated with emotional experiences, the amygdala has an important function in emotional learning. It also participates in the regulation of sexual behavior, aggressive behavior, and fear.
The hippocampus is a seahorse-shaped structure located in each of the temporal lobes of the brain. It is part of the limbic system. The hippocampus is one of the brain structures where neurogenesis is known to occur, a feature that strongly contributes to its key roles in memory and learning. Its main functions include memory consolidation from short to long-term and the formation and recall of spatial memory. It also has important functions in spatial navigation.
The thalamus is a brain structure located between the cerebral cortex and the brain stem. It is a major relay station, particularly for sensory information, receiving and processing information from every sensory system (except the olfactory system) and transmitting it to correspondent area of the cerebral cortex. It is also associated with motor control, language, and with the regulation of sleep, wakefulness, alertness and consciousness.
The cingulate gyrus is a structure that is part of the limbic system. The cingulate gyrus is involved in the formation and processing of emotions, in learning, in memory, and in executive functions. It has a key role in learning by linking behavioral outcomes to motivation and emotion. The cingulate gyrus is involved in predicting and avoiding negative consequences and in controlling conscious responses to unpleasant experiences.
The neuroendocrine system is a functional interaction between the nervous and the endocrine systems through which the body’s physiological processes are regulated. The neuroendocrine system regulates blood pressure, feeding and drinking behavior, metabolism, energy expenditure, reproduction, and maintains homeostasis. The hypothalamus is the main gland of the neuroendocrine system.
The endocrine system is a signaling system that acts through the action of hormones. It is made up of the all the glands and endocrine organs that secrete hormones directly into the bloodstream to be carried to other organs where they will act to modulate their function. The endocrine structures in the brain are the hypothalamus, the pituitary gland and the pineal gland.
The hypothalamic–pituitary–adrenal (HPA) axis refers to the interaction system between the hypothalamus, the pituitary gland, and the adrenal glands. The HPA axis is part of the neuroendocrine system. It has a key role in regulating homeostasis and energy storage and expenditure. It controls the responses to stress, regulates mood and emotions, and participates in the regulation of digestion, immune functions, and sexuality.
The pineal gland is a small endocrine gland located in the brain. Its main function is to produce melatonin, a hormone derived from serotonin, which regulates circadian rhythms and modulates sleep patterns.
The hypothalamus is a structure located at the base of the brain whose major function is to act as a link between the nervous and the endocrine systems. The hypothalamus acts primarily on the pituitary gland (hypophysis) by producing neurohormones that can either stimulate or inhibit its secretion of other hormones. The hypothalamus is part of the limbic system and its main functions include the control of hunger, thirst, body temperature, sleep, circadian rhythms, and fatigue.
The pituitary gland (or hypophysis) is a small endocrine gland located at the base of the brain and regulated by the hypothalamus. The posterior lobe of the pituitary gland (the neurohypophysis) communicates directly with the hypothalamus, being the region where axons coming from the hypothalamus end; the anterior lobe (the adenohypophysis) secretes hormones and regulates a number of physiological processes such as stress, temperature, pain, growth, and reproduction.
The adrenal glands (or suprarenal glands) are endocrine glands located above the kidneys. The adrenal glands produce numerous hormones involved in the regulation of stress response, metabolism, and homeostasis, for example. The adrenal gland produces adrenaline and noradrenaline. Unlike the brain, where noradrenaline is produced in higher quantities, in the adrenal glands adrenaline is the main catecholamine produced, with most of the circulating adrenaline being synthesized there, with only a small amount of noradrenaline being produced by the adrenal glands.
Micro Neuro Anatomy
Neurons are nerve cells, the basic element of the nervous system. They specialize in receiving, processing, and transmitting information using chemical and electrical signals. Neurons work together in the form of neuronal networks to give rise to thoughts, behaviors, memories, sensations, and emotions. There are around 86 billion neurons just in the brain.
A synapse is a communication interface that allows a neuron to transmit information to another neuron in the form of a chemical or electrical signal. Each neuron can have hundreds to thousands of synapses, thereby multiplying the number of connections and pathways in neuronal networks. The number of synapses in the human brain is estimated to be around 150 trillion.
Dendrites are the smaller projections of neurons. They are branched structures that stem from the neuron’s cell body. They typically receive the information coming from other neurons through synapses and transmit it in the form of electrical impulses to the neuron’s cell body.
The axon is the long and slim projection of a neuron. The axon is the structure that typically transmits information away from the cell body in the form of electrical impulses, and then communicates it to other neurons through synapses.
Neurites are the projections of neurons, used to receive and transmit information in the form of electrical impulses. Neurites include the axon and the dendrites.
A neural network is a set of interconnected neurons that act together to perform a specific function. In a neural network, neurons are functionally connected through their neurites and synapses.
A connectome is a map of the neuronal interactions in the brain. A connectome describes the networks of functional and anatomical connections across the brain.
Mirror neurons are neurons that fire both when one is performing a certain action or observing that action being performed by another. They therefore “reflect” the behaviors of other individuals. Mirror neurons are speculated to be involved in empathy, understanding intentions, and learning by imitation, including learning motor processes and language.
Glial cells are non-neuronal cells of the nervous system. They are present both in the central and in the peripheral nervous systems, where there are different types of glial cells with specialized functions. Glial cells surround neurons such as to provide structural and nutritional support, insulate them by producing myelin, and remove cellular waste products, dead cells, toxins and pathogens. Glial cells also play an important part in neuronal communication, both by being able to produce neuroactive molecules that modulate neuronal activity, and by participating in synaptic transmission.
Stem cells are undifferentiated cells that still have not acquired specific characteristics and functions. They have the ability to differentiate into specialized cells, which means that they can become any type of cell from the tissue in which they are found, being able to maintain and repair it. They also have the ability to self-renew, maintaining a constant pool of undifferentiated cells.
Neural Stem Cell:
Neural stem cells undifferentiated cells from the nervous system that still have not acquired specific characteristics and functions. They have the ability to self-renew and to differentiate into the specialized cells of the nervous system, be it neurons or glial cells.
Myelin is a substance that envelops the axons of some neurons (myelinated neurons). Myelin is an electric insulator whose main function is to increase the speed at which electrical impulses propagate in axons. It is produced by oligodendrocytes in the central nervous system and by Schwann cells in the peripheral nervous system (both are glial cells).
The extracellular matrix is a support structure for cells. It makes up the space between different cells in a tissue, giving them physical and chemical support and aiding in intercellular communication.
Capillaries are the smallest type of blood vessels. Due to their extremely thin wall, with only one layer of cells, capillaries allow the exchange of water, oxygen, carbon dioxide, nutrients and cellular waste between the blood and the tissues.
Neurotransmitters are the main chemical messengers of neurons. They are molecules that are usually produced in neurons and released in synapses when neurons are activated, acting on other neurons in order to transmit a signal.
Acetylcholine is a neurotransmitter formed from acetate and choline. It acts on specific acetylcholine receptors located in the cell membrane. In the peripheral nervous system, acetylcholine is the neurotransmitter that motor neurons secrete to activate muscles, and the main neurotransmitter of the parasympathetic nervous system. In the central nervous system, acetylcholine acts as a neuromodulator, having an important role in attention mechanisms.
Catecholamines are a family of organic compounds derived from the amino acid tyrosine. Dopamine, noradrenalin and adrenalin are all catecholamines, having L-DOPA as a common precursor.
Dopamine is a neurotransmitter from the catecholamine family. It acts on specific dopamine receptors located in the cell membrane. It is synthesized in the brain and is a key neurotransmitter in mood, reward-motivated behavior, executive functions and motor control.
Norepinephrine (or noradrenaline) is a neurotransmitter and hormone from the catecholamine family. It acts on specific adrenergic receptors located in the cell membrane. In the peripheral nervous system, norepinephrine is the main neurotransmitter of the sympathetic nervous system. In the central nervous system, norepinephrine has an important role in attention, alertness and memory.
Epinephrine (or adrenaline) is a hormone from the catecholamine family. It acts on adrenergic receptors located in the cell membrane that also respond to norepinephrine. Epinephrine is associated with the emotional response to stressful situations. Epinephrine has an important role in emotional memory encoding and consolidation.
Serotonin (or 5-hydroxytryptamine – 5-HT) is a monoamine neurotransmitter. It is mostly found in the central nervous system and in the gastrointestinal tract. It acts on 5-HT receptors located in the cell membrane. Serotonin regulates mood, appetite, sleep, memory and learning.
GABA (gamma-Aminobutyric acid) is the main inhibitory neurotransmitter of the nervous system. It acts on receptors found in neurons’ cell membrane, the GABAA and GABAB receptors, reducing the excitability of those neurons.
Glutamate is the main excitatory neurotransmitter of the nervous system. It acts on receptors found in neurons’ cell membrane, such as the NMDA and AMPA receptors, inducing the activation of those neurons. Glutamate has a key role in synaptic plasticity and long-term potentiation, and is essential for learning and memory functions.
Histamine is a molecule that acts as a neurotransmitter in the nervous system. It acts on histamine receptors located in the cell membrane. In the nervous system, histamine’s functions include the promotion of wakefulness, and the regulation of appetite and body temperature. It can also have an inhibitory effect on synaptic transmission. In the immune system, histamine is released during immunological responses to allergens.
Adenosine is a purine nucleoside that acts as a neuromodulator in the nervous system. It acts on adenosine receptors located in the cell membrane. Adenosine is also part of the structure of ATP and cAMP. In the nervous system, adenosine has an inhibitory effect, decreasing arousal and promoting sleep.
Other Neuro Signaling Chemicals:
A neurohormone is a messenger molecule (hormone) that is synthesized and released by neuroendocrine cells into the bloodstream as a response to a neuronal signal. Neurohormones can act as neurotransmitters.
Neuropeptides are chemical messengers of the nervous system composed of short amino acid sequences. They are released by neurons (and glia) and act on other neurons in order to modulate their activity.
Opioids are substances that have morphine-like actions mediated by the activation of opioid receptors. Opioids act mainly on the central nervous system and their main effect is pain relief.
Endorphins are endogenous opioid neuropeptides, i.e., opioid molecules that are produced by the body, namely by the central nervous system and the pituitary gland. They act on opioid receptors located in the cell membrane and their main effects are pain relief and increased feelings of euphoria.
A ligand is a substance that binds to another molecule, such as a receptor, for example, in order to perform a specific function. The binding of a ligand usually induces a structural change that functionally alters the molecule to which it binds.
An ion is an atom or a molecule with an electrical charge. Ions are called anions when they have negative charge, and cations when they have positive charge.
The receptor site is the area of a neuron’s cell membrane where interaction with extracellular molecules occurs. These molecules can be neurotransmitters, neuropeptides, neurohormones, or other mediators. These chemical mediators bind to molecules that specifically recognize them, the receptors, and give rise to intracellular signals that are then processed by the neuron and originate a physiological response, such as an electrical impulse.
NMDA (N-methyl-D-aspartate) is a receptor for the excitatory neurotransmitter glutamate. It is found in neurons and has a key role in synaptic plasticity, memory and learning. The NMDA receptor is an ion channel that is activated when glutamate and glycine (or D-Serine) bind to it. When activated, it allows positively charged ions to flow through the neuron’s cell membrane, potentially inducing an electrical impulse.
AMPA (α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid) is a receptor for the excitatory neurotransmitter glutamate. It is found in neurons and has a key role in fast synaptic transmission, synaptic plasticity, long-term potentiation and, consequently, in memory and learning. When activated, it allows positively charged ions to flow through the neuron’s cell membrane, potentially inducing an electrical impulse.
Nicotinic receptors are receptors for the neurotransmitter acetylcholine. They are found mostly in the brain, autonomic ganglia and in the neuromuscular junction.
Neurotrophins are large protein growth factors produced in the nervous system that support the growth and survival of brain cells.
BDNF (brain-derived neurotrophic factor) is a neurotrophin, i.e., a protein that induces the development, growth and survival of neurons. BDNF can modulate synaptic transmission, playing an important role in long-term memory. BDNF is also one of the most important molecules contributing to neurogenesis, the growth of new neurons from neural stem cells.
NGF (nerve growth factor) is one of the most important neurotrophins, i.e., a protein that induces the development, proliferation, growth and survival of neurons. NGF is essential for the survival of sympathetic and sensory neurons. NGF also plays an important part in learning ability. NGF increases pain perception in inflammatory conditions.
GDNF (glial cell-derived neurotrophic factor) is a neurotrophin, i.e., a protein that induces the development, proliferation, growth and survival of neurons. GDNF has a key role in supporting the survival of dopaminergic and motor neurons.
Enzymes that transform or break down neurotransmitters in synapses.
MAO (L-Monoamine oxidase) is a family of enzymes that catalyze the oxidation of monoamine neurotransmitters and neuromodulators, thereby inactivating them. These include serotonin, dopamine, noradrenaline, and adrenaline.
COMT (Catechol-O-methyltransferase) is an enzyme that degrades catecholamines, thereby inactivating them. These include dopamine, noradrenaline, and adrenaline.
Acetylcholinesterase is the enzyme that degrades acetylcholine, thereby inactivating it.
Hydroxylases are enzymes that introduce a hydroxyl group into an organic compound. Dopamine β-hydroxylase, the enzyme that converts dopamine into noradrenaline is an example of such enzymes.
A vesicle is a small enclosed structure found in cells. Vesicles are used in a number of cellular processes such as secretion, uptake and transport of molecules. In neurons, synaptic vesicles are used to store and release neurotransmitters at synapses.
Cytokines are small signaling molecules produced by a wide variety of cells. They act on specific receptors located on the cell membrane. In the nervous system, cytokines can modulate a number of functions, namely neurotransmission and neuroinflammation.
Calcium Ion Channel:
Ion channels are proteins found in cells’ membranes that form a pore through which ions can flow. In the nervous system, calcium ion channels allow the flow of calcium through the neuronal cell membrane, having important functions in neurotransmitter release at synapses.
Beta Amyloid (or amyloid beta, Abeta, Aβ) is a peptide that has a key role in Alzheimer’s disease. Beta amyloid is the main component of the amyloid plaques. These structures are toxic to nerve cells and are found in the brains of Alzheimer’s patients.
The cell membrane (or plasma membrane) is a structure that envelops a cell, isolating the interior of the cell from the exterior environment. The cell membrane has selective permeability, allowing a controlled movement of substances in and out of cells.
Receptors are proteins located in the cell membrane that receive signals from the outside and transmit them to the inside of the cell to generate a response. Each receptor is activated by specific molecules (the ligands) and originates a specific intracellular response.
Mitochondria are cellular organelles that generate most of the cell’s energy in the form of ATP. They are also involved in other cellular functions such as cell differentiation, metabolism, growth and death, calcium storage, and signaling.
DNA (deoxyribonucleic acid) is the molecule that contains all the genetic information of a cell or organism.
RNA (ribonucleic acid) is a molecule used to translate the genetic information contained in the DNA in order to produce proteins. Some specific types of RNA are also used in cellular signaling and in the control of gene expression and biological reactions.
A gene is a region of the DNA that contains the information needed to assemble a specific protein.
Nucleotides are a type of organic molecule that forms the building block of nucleic acids – DNA and RNA. Nucleotides are composed of a nucleoside (a nitrogenous base and a five-carbon sugar) and at least one phosphate group. Nucleotides are also a source of metabolic energy (e.g. ATP), participate in cell signaling (e.g. cAMP), and are important cofactors of enzymes (e.g. NAD).
The genome is the totality of the genetic information of an organism. It includes all the genes and all the regulatory regions of the DNA.
The epigenome is the set of chemical changes to the DNA (without altering the DNA sequence) of an organism that can alter the functions of its genome. Unlike the DNA sequence that remains unaltered, the epigenome is dynamic and is the result of environmentally-induced changes. Epigenetic changes are associated with the regulation of gene expression, development, and tissue differentiation.
The microbiome is the complete pool of genomes of all the microorganisms that exist in a specific ecosystem. For example, the gut microbiome is the collection of the genomes of all microbes that reside in the gut.
The metabolome is the complete pool of all small molecules found in a specific biological sample, be it a cell, an organ, or an organism. Those small molecules include naturally produced metabolites, such as amino acids, sugars, fatty acids, nucleic acids, vitamins, pigments, antibiotics, and so forth, as well as exogenous chemicals, such as drugs, additives, toxins and other foreign chemicals.
The telomere is a region at each end of a chromosome that contains repetitive nucleotide sequences which protect the end of the chromosome. Given that each time the DNA is duplicated the end of the chromosome is shortened, the repetitive sequence of the telomere prevents the loss of important genetic information.
ATP (adenosine triphosphate) is the source of chemical energy in cells. It is mainly used as a source of energy in metabolic processes, but it is also used in signaling pathways and in the production of the messenger molecule cAMP. ATP is continuously used and recycled in cells.
AMPK (5′ adenosine monophosphate-activated protein kinase) is an enzyme with a key role in cellular energy homeostasis. AMPK can sense the AMP:ATP ratio, which is used by cells to determine how much energy is available, so that they can direct their metabolic process towards the production or the use of ATP, as needed.
NAD (nicotinamide adenine dinucleotide) is a coenzyme found in all cells with important functions in cellular metabolism. It participates in redox reactions, transferring electrons between molecules. It is found in two forms – NAD+ is an oxidizing agent that accepts electrons from other molecules, forming NADH; NADH is a reducing agent that donates electrons to other molecules, forming NAD+ again. NAD is also a substrate for a number of enzymes.
Sirtuins are a class of proteins that can regulate important biological processes. Sirtuins can control mitochondrial biogenesis, influencing the cell’s energy reserve. Sirtuins can also affect aging, cell death, inflammation, and stress resistance.
PDEs (phosphodiesterases) are enzymes that can break a phosphodiester bond. The phosphodiester bond is found in many essential molecules, such as the DNA, the RNA or the messenger molecule cAMP. In the case of cAMP, breaking the phosphodiester bond inactivates this molecule.
cAMP (3′,5′-cyclic adenosine monophosphate) is an intracellular signaling molecule with key roles in many biological processes. It is synthesized from ATP by adenylate cyclase and degraded to AMP by phosphodiesterase.
Sodium/ Potassium Pump:
The sodium/potassium pump (or sodium-potassium adenosine triphosphatase) is an enzyme that pumps sodium out of cells while pumping potassium into cells, against their concentration gradients, and using energy from ATP. The sodium/potassium pump is essential in neuronal physiology by maintaining the membrane’s resting potential.
Physiology / Processes
Neurogenesis is the generation of new neurons from progenitor cells or from neural stem cells.
Synaptogenesis is the generation of new synapses in the nervous system.
Angiogenesis is the generation of new blood vessels from preexisting vessels. It can occur by sprouting or by splitting of blood vessels.
Biogenesis is the generation of new living organisms from existing living organisms.
Neuroprotection is the defense of the structure and function of neuronal tissue.
Neuroplasticity refers to enduring changes that occur in the brain throughout life. These changes can affect individual neurons, or the whole brain, as occurs after brain damage. Neuroplasticity can be induced by experiences, thoughts, and emotions, and it is the basis of cognitive processes such as learning and memory.
Synaptic plasticity is the capacity of synapses to strengthen or weaken over time due to increased or decreased activity. It is also affected by local neurotransmitter release. Synaptic plasticity is a key mechanism in learning and memory.
Perfusion is the circulation of blood through the capillary vessels of a tissue.
Transcription is the process through which the information contained in a DNA sequence is copied to RNA (mRNA), the first step of gene expression. The mRNA sequence synthesized during transcription is then used to produce proteins.
Inflammation is a biological response to injury or harmful agents characterized by the production of chemical mediators, increased blood flow, and infiltration of immune cells into affected tissues. These processes act together to remove threat and/or repair damaged tissue.
Oxidation is a chemical reaction that causes the loss of electrons by a molecule. Oxidation reactions are important in many biological processes, but may be harmful when free radicals are produced as part of the reaction without being immediately bound by a redox molecule or an antioxidant. Free radicals can induce mutations and contribute to aging.
Excitotoxicity is a detrimental process by which neurons are damaged or die due to excessive stimulation by excitatory neurotransmitters. It occurs mostly when excessive glutamate excessively activates its receptors.
Apoptosis is the biological process of programmed cell death. Apoptosis is a controlled process mediated by an intracellular program and signaling pathways.
Vasodilation is the widening of blood vessels and vasoconstriction is the narrowing of blood vessels. These processes regulate blood flow and blood pressure. Vasodilation can occur when tissues are in need of oxygen or nutrients.
Signal transduction is a process through which the activation of a receptor by an extracellular molecule induces a cascade of events inside the cell, leading to a specific response.
Long Term Potentiation:
Long-term potentiation (LTP) is the enduring strengthening of synapses due to a repeated activity pattern. LTP is a mechanism of synaptic plasticity. LTP is a key mechanism in learning and memory.
Metabolism is the set of chemical and enzymatic reactions that occur in living organisms to sustain life. Metabolism includes the breakdown of molecules to obtain energy (catabolism) and the synthesis of all molecules needed by cells (anabolism).
Chemistry / Nutrients
Amino acids are a class of organic compounds that contain an amine and a carboxylic acid functional group. Besides these groups, each amino acid has a specific side-chain. They are the building blocks of proteins. Some neurotransmitters are also amino acids, as is the case of glutamate and GABA.
Peptides are biomolecules consisting of short sequences of linked amino acids. Longer chains are called proteins.
Proteins are large biomolecules consisting of one or more long sequences of linked amino acids. Proteins are assembled using information encoded in genes in the DNA.
Enzymes are proteins that increase the rate of a chemical reaction, in a process called catalysis. Enzymes transform a substrate (the initial molecule) into a final product at a high speed, lowering the energy needed for that reaction to occur. They are essential to all metabolic processes.
A vitamin is a vital nutrient that an organism requires only in limited amounts, but cannot synthesize in sufficient amounts, thus having to be obtained through the diet.
A mineral is an inorganic compound. Mineral nutrients are the elements required by living organisms other than carbon, hydrogen, nitrogen, and oxygen, present in organic compounds. The major mineral nutrients in the human body are calcium, potassium, sodium, magnesium, phosphorus, sulfur, and chlorine.
An antioxidant is a compound that inhibits the oxidation of other molecules. A number of antioxidants are naturally produced by the body, but they can also be obtained through diet. Antioxidants are important in preventing oxidative damage caused by free radicals.
Fatty acids are carboxylic acids with a long chain of carbon atoms. Fatty acids are part of the structure of triglycerides (fat) and phospholipids of cellular membranes. Fatty acids are an important biological fuel since their metabolism produces high amounts of energy in the form of ATP.
Cholesterol is a lipid synthesized by all animal cells. It is an essential component of cell membranes. Cholesterol is also a precursor of steroid hormones. However, excessive levels of cholesterol are harmful and are associated with a number of disease, namely cardiovascular conditions.
Phospholipids are a class of lipids made up of two fatty acids, a glycerol molecule, and a phosphate group. They are the main component of cell membranes.
Sugar (Glucose, Ribose):
Sugars are carbohydrates. Simple sugars, such as glucose or fructose, are short chains of carbon, oxygen and hydrogen atoms. They are used in many metabolic pathways and are used to produce energy in the form of ATP. They are also components of the structure of many important molecules, such as DNA (deoxyribose), RNA (ribose), or ATP (ribose).
Nutrients are elements or molecules found in food that are needed for survival and growth. These include sugars, fats, proteins, vitamins, minerals, and water.
A chelate is a compound formed by the binding of ions or molecules to metal ions. This process allows the sequestration of metal ions, reducing their reactivity. Chelation is an important process in the removal of toxic heavy metals from the body, and in the delivery of otherwise unstable metal ions to the body, for example.
Redox is a type of chemical reaction that requires the reduction and oxidation of molecules. It involves the transfer of electrons between molecules. Oxidation refers to the loss of electrons, while reduction is the gain of electrons. Redox reactions are important in many biological processes.
A free radical is a highly reactive atom, ion or molecule. Their high reactivity is due to the existence of unpaired valence electrons, a highly unstable chemical state. Free radicals play an important role in many biological processes. However, due to their high instability and reactivity, free radicals can also undergo undesired side reactions that lead to cell damage or even cell death.
Methylation is a chemical reaction that adds a methyl group to a molecule, altering its function. This reaction is catalyzed by enzymes and occurs in many biological processes such as regulation of gene expression and protein function.
Phosphorylation is a chemical reaction that adds a phosphoryl group to a molecule. Phosphorylation and dephosphorylation are processes that can activate or deactivate a number of enzymes and other proteins.
Glycation is a chemical reaction that adds a sugar molecule to a protein or lipid molecule. This reaction does not use enzymes. When enzymes are used, this reaction is called glycosylation. Glycation is a random reaction that can damage biomolecules, whereas glycosylation is a controlled process.
Glycolysis is a key metabolic process that converts glucose into pyruvate, acetate and hydrogen while producing energy in the form of ATP and NADH.
Lipid is a collective term for a group of molecules that includes triglycerides (fat), sterols, phospholipids, and others. Lipids are important as structural components of cell membranes, in energy production and storage, and cell signaling.
Fat-soluble is the property of being able to dissolve in nonpolar solvents, such as fats, oils, and lipids in general.
Water-soluble is the property of being able to dissolve in water.
The Krebs cycle (or citric acid cycle, or tricarboxylic acid) is an important cyclic metabolic pathway that generates energy in the form of GTP through the oxidation of acetyl-CoA derived from carbohydrates, fats and proteins. It also produces carbon dioxide, NADH and precursors of certain amino acids.
Xanthines are a group of alkaloid molecules with stimulant activity that act by inhibiting the actions of adenosine in the central nervous system, increasing alertness and decreasing sleepiness. Caffeine, theobromine, and theophylline are methylated xanthines. They can inhibit phosphodiesterase, thereby increasing the levels of intracellular cAMP, and reduce inflammation.
Steroids are organic compounds with biological functions. Steroids can be hormones (steroid hormones), signaling molecules, and components of cell membranes (e.g. cholesterol).
Ketones are organic compounds that contain a ketone group. They participate in numerous biological reactions, such as fatty acid synthesis or the Krebs cycle. Many sugars are ketones (ketoses), such as fructose, for example.
pH is a scale that defines the acidity or basicity of aqueous solutions. It ranges from 0 to 14, with 7 corresponding to a neutral solution, values below 7 referring to acid solutions, and values above 7 referring to basic solutions.
Osmosis is the spontaneous movement of solvent molecules through a semipermeable membrane to a region of higher solute concentration, such as to balance the concentration of solute on the two sides of the membrane. The osmotic gradient corresponds to the difference in concentration between the two solutions and defines the amount of solute needed to create an equilibrium.
Oxygen is a chemical element. It is highly reactive and an oxidizing agent that promptly forms compounds with most elements. Most major classes of organic molecules contain oxygen, namely carbohydrates, proteins, fats and nucleic acids.
Neuroimaging is the visualization of the nervous system using techniques that allow the direct or indirect imaging of its structural or functional aspects. Structural neuroimaging deals with the structure of the nervous system and with large scale organization, disease, and injury. Functional neuroimaging deals with the processing of information by the brain, metabolic aspects, and small scale organization.
MRI (magnetic resonance imaging) is an imaging technique that uses strong magnetic fields, radio waves, and field gradients to visualize the anatomy and physiological processes of the body.
Functional MRI (fMRI) is an functional neuroimaging technique that allows the assessment of brain activity. fMRI measures differences in blood oxygenation as a contrasting method, allowing to determine which areas of the brain are activated at a given moment or in reaction to a stimulus by detecting changes in blood flow, an indication of increased local neuronal activation.
SPECT (Single-photon emission computed tomography) is an imaging technique that uses radiation (gamma rays) to do a 3D scan of brain activation. SPECT is a type of computed tomography (CT). In SPECT, a radioisotope that emits gamma rays is attached to a ligand and administered to the body, usually into the bloodstream. The properties of the ligand allow it to bind to specific types of tissues. Gamma ray emissions are assessed, serving as measure of the concentration of the ligand in a given brain region. This concentration serves as an indication of the blood flow in that region, and consequently, as an indication of local neuronal activation.
CT (computed tomography), also known as CAT scan (computerized axial tomography scan) is an imaging technique that uses a combination of X-ray images taken from different angles to produce cross-sectional images of specific areas of the brain. A 3D image of the brain is obtained from a series of 2D radiographic images taken around an axis of rotation.
PET (positron emission tomography) is a functional imaging technique that is used to assess neuronal activation through the visualization of metabolic activity. This technique uses a positron-emitting radionuclide, or tracer, delivered into the body bound to a biologically active molecule. The emission of gamma rays by the tracer is used to indicate its relative concentration in the analyzed area, serving as an index of the metabolic activity in that region. Images of the tracer’s concentration are obtained with the support of a CT X-ray scan, originating 3D images of brain activation.
MEG (magnetoencephalography) is a functional neuroimaging technique that is used to assess brain activity through the recording of magnetic fields produced by neuronal activity. These magnetic fields are generated by the ionic currents running in the neurites of neurons during the conduction of electrical impulses.
DOT (diffuse optical tomography) is an imaging technique that creates 3D models of the brain using light in the near-infrared region. It allows the observation of brain activity in a natural state. DOT uses the different light absorption properties of oxygenated and deoxygenated hemoglobin to generate images that represent the activation of brain regions.
EROS (event-related optical signal) is a neuroimaging technique that uses infrared light to assess changes in optical properties of active regions of the cerebral cortex. EROS uses the light-scattering properties of neurons to obtain a direct and high-resolution measure of neuronal activity.
Ultrasound, or ultrasonography, is an imaging technique that uses high-frequency sound waves (inaudible to humans) to visualize internal body structures. Pulses of ultrasound are sent into tissues and their reflection is used to generate real-time images of those tissues.
Brainwaves are produced when regions of neurons fire together forming synchronized electrical pulses. They relate to states of consciousness and what we are feeling and doing.
Beta brain waves are a type of rhythmic or repetitive neural activity that originate from states associated with normal waking consciousness and reasoning. Beta waves are associated with active thinking, active concentration, and intensified states of alertness, logic and critical reasoning. They can also be associated with anxious thinking, translating into stress and restlessness.
Alpha brain waves are a type of rhythmic or repetitive neural activity that originate from the visual cortex in the occipital lobe during wakeful relaxation with closed eyes. Alpha waves are reduced with open eyes, drowsiness and sleep and they represent neuronal activity in a wakeful resting state.
Theta brain waves are a type of rhythmic or repetitive neural activity that are present during meditative or drowsy states, and in light and REM sleep.
Delta brain waves are a type of rhythmic or repetitive neural activity that are present during deep non-REM sleep, also known as slow-wave sleep (SWS).
Gamma brain waves are a type of rhythmic or repetitive neural activity that are present during simultaneous processing of information from different brain areas, and that may modulate perception and consciousness.
EEG (electroencephalography) is a brain monitoring method that records the electrical activity of the brain. In EEG, electrodes are placed along the scalp and the brain’s spontaneous electrical activity is measured. EEG measures the summation of voltage changes resulting from the synchronized activity of thousands or even millions of neurons. These brain waves can be associated with different states of brain functioning.
Coherence measures neuronal patterns of synchronous oscillatory activity (brain waves), and the frequency and amplitude of that synchronous activity. Coherence can be used to determine if different brain regions have similar brain waves. Since coherent oscillations between different brain regions are associated with the generation of functional connections and neuronal networks, coherence is also used to determine functional relationships between different brain areas involved in the generation of those synchronous brain waves.
Voltage is a measure of the difference in electrical potential energy between two points in an electric circuit. The greater the voltage, the greater the flow of electrical current between those points. In a neuron, for example, there is a difference of potential energy (or voltage) between the inside and the outside of the axon’s cell membrane. When a neuron is activated, this voltage causes an electric current across the cell membrane that propagates along the axon.
An impulse, or action potential, is a sudden variation in the voltage of an axon’s cell membrane that causes an electric current across the membrane. This electrical current flow is then propagated along the membrane, allowing the transmission of the electrical impulse along the axon.
A conductor is a structure, material or object that allows the flow of an electrical current.
An insulator is a structure, material or object that does not allow the free flow of an electrical current.
Computation can be defined as the act of performing a calculation. In a neurological context, computation refers to information processing by the brain, including structuring, managing, and integrating different kinds of information, so that a thought or behavior can arise.
Endogenous refers to compounds or mechanisms originating from within a cell, tissue or organism.
Exogenous refers to compounds or mechanisms originating from outside a cell, tissue or organism.
Dependence is a state associated with repeated exposure to a stimulus that leads to a withdrawal syndrome when that repeated exposure is interrupted. The withdrawal symptoms can be physical, such as fatigue or headaches (physical dependence), or psychological, such as unease or anxiety (psychological dependence).
Downregulation is a decrease in the cellular production of a given compound in response to a stimulus or another variable.
Upregulation is an increase in the cellular production of a given compound or in receptor sensitivity to that compound in response to a stimulus or another variable.
Cycling is the chemical process of creating cyclic bonds in molecules, leading to the formation of ring structures.
An agonist is a compound that binds and activates a receptor inducing a biological response.
An antagonist is a compound that blocks the agonist-induced activation of a receptor. Antagonists do not elicit biological responses, but they hinder the interaction of an agonist with its receptor, inhibiting its function.
A transporter is a membrane protein that allows the movement of molecules through a biological membrane.
A reuptake inhibitor is a molecule that blocks the reabsorption of a neurotransmitter from the synapse. Reuptake occurs through transporter proteins located in the membrane of presynaptic neurons. Their inhibition leads to an increase in the neurotransmitter’s extracellular levels and, consequently, an increase in their effect.
A reuptake enhancer is a molecule that increases the reabsorption of a neurotransmitter from the synapse. Reuptake occurs through transporter proteins located in the membrane of presynaptic neurons. Their enhancement leads to a decrease in the neurotransmitter’s extracellular levels and, consequently, a decrease in their effect.
A nutraceutical (from nutrition + pharmaceutical) is a product derived from food sources that has health benefits beyond its basic nutritional value. Nutraceuticals can be used to support and enhance well-being, or to control and prevent diseases or their symptoms.
A botanical extract is a substance obtained from plants through a chemical separation process using a solvent such as water or ethanol.
A synthesized chemical is a compound obtained from a reproducible laboratory chemical reaction specifically designed to produce it.
Orthomolecular is a term that literally means “the right molecule”. It expresses the idea of preventing or treating a condition with the optimal amount of a substance that is natural to the body, taking into account each individual’s biochemistry.
Neurotoxins are substances that have harmful or toxic effects to neurons, unfavorably affecting their function.
A nootropic is a substance that can enhance one or more aspects of cognitive function, such as memory, learning, attention or motivation, for example. It can be a functional food, a nutraceutical, a supplement, or a drug.
A stimulant is a psychoactive substance that can temporarily enhance the activity of the nervous system, leading to an increase in mental and/or physical functions. Stimulants can potentiate mood, wakefulness, alertness, and motor functions.
An anxiolytic is a psychoactive substance that reduces anxiety.
An empathogen is a psychoactive substance that potentiates emotional experiences by producing a state of enhanced empathy and sympathy.
An entheogen is a psychoactive substance that is used with the intent of potentiating mystical, spiritual, or religious experiences.
An euphoriant is a psychoactive substance that induces euphoria, i.e. a strong feeling of excitement, happiness and well-being.
An analgesic, or painkiller, is a substance that acts on the nervous system to induce pain relief.
A cholinergic is a substance that acts on the nervous system to increase the production or release of acetylcholine, or to mimic its effects by acting on its receptors.
An adrenergic is a substance that acts on the nervous system to increase the production or release of noradrenaline or adrenaline, or to mimic its effects by acting on its receptors.
An anabolic is a substance that stimulates metabolic pathways that build compounds from smaller molecules using chemical energy in the form of ATP.
Proprioception is the sense of oneself. It refers to one’s body awareness, the perception of equilibrium, motion, and of the position of body parts, as well as of the effort need to make a movement.
Sensory acuity refers to the sharpness and relative capacity of the senses in acquiring information.
Reaction speed is a measure of the time between the occurrence of a sensory stimulus and the subsequent behavioral response to that stimulus. It is an index of the brain’s speed in processing all the mental mechanisms needed for a response to a stimulus to occur.
Movement precision is a measure of the accuracy of motor actions and of one’s control over those actions.
Spatial awareness is the sense of oneself in space. It is the perception of objects in relation to each other and to oneself in a given space. It is the ability to understand the location, placement, distance, movement, and speed of objects in relation to their surroundings and to oneself.
Spatial intuition is the immediate understanding of spatial relations without previous knowledge of those relations. It’s the unreasoned understanding of the location, placement, distance, movement, and speed of objects in relation to their surroundings and to oneself.
Peripheral awareness is the ability to sense and locate objects, sounds or actions or that are outside one’s direct line of focus. It is the perception of what is going on around oneself.
Cognitive Science / Psychology
A psychological function dedicated to preserving information, typically thought to involve the processes of encoding, storage, and retrieval. Human memory is a complex nested system of different interrelated functions, which recruit distinct brain regions and mechanisms, including declarative memory (for factual information), procedural memory (for information about how to carry out sequences of operations), and muscle memory (for sensorimotor activities). There is also a general division between working/short-term memory and long-term memory, which are likewise parsed according to the differential recruitment of brain regions and mechanism.
Short Term Memory:
A memory system capable of holding a limited amount of information for brief periods, of up to approximately 30 seconds to 1 min. Storage capacity for short term memory has been shown to have a limit at about seven items or “chunks” of information. Essential for language processes, reading, and all complex sequenced behaviors.
Long Term Memory:
A memory system containing information that is stored for periods ranging from over 1 min to many decades. Issues of storage capacity and degradation of information are important, as long-term memory is essential for identity formation as well as complex forms of learning and expertise.
The process whereby information is transferred from short-term memory to long-term memory, and then integrated with existing networks of complex long-term memories. This process is largely unconscious and continues for some time after exposure to new information.
A temporary store for recently engaged items of information that are currently occupying consciousness and that can be manipulated and moved in and out of short term memory. First put forward by Baddeley and Hitch in 1974, it has been theorized to consist of a central executive and two buffer stores, called the called the phonological loop and the visuospatial sketch pad.
A type of long term memory for factual information about the world, often distinguished from episodic memory and procedural memory. A typical example being the dates of the Second World War or the key aspect of a theoretical model.
The memories formed during the process of motor learning that are often not accessible to conscious recall, but instead are expressed in the contexts of motor performance in which they were acquired. A typical example is learning to play a musical instrument or swing a golf club, where one can improve performance through practice without explicit and articulate memory formation taking place.
A type of long term memory for personal experiences and events. Stored as information about specific events occurring at particular time and places, it affords a sense of personal continuity and familiarity with the past.
Sustained concentration on a specific stimulus, sensation, idea, thought, or activity, enabling one to use information processing systems optimally in handling vast amounts of information available from the sense organs and memory stores. Attention is often thought of in terms of “span” and intensity.
The act or power of focusing attention or mental effort, usually in the pursuit of some goal or in the carrying out of some action.
The ability to intentionally narrow in on one object, task, or train of thought, despite possible distractions.
The active manipulation of semantic or intentional realities in a way that depends only on their formal properties. Key to the approach known as “cognitivism” or the computational theory of mind, and central to the assumptions of modern cognitive science, the idea is that human minds and computers share the trait of being fundamentally computational, where this is taken as involving information processing based on the manipulation of symbols independent from their semantic properties (i.e., both humans and computers are formal symbol manipulators).
The temporal quickness or expediency with which computations are carried out, often a function of processing power.
The extent of the depth and breadth (abstraction and complexity) of the information that can be handled by a computational engine, be it a computer or a human mind. The greater the processing power the greater the complexity and abstraction that can be computed, and the faster the rate at which it can be done.
The act or process of formulating a general concept by identifying common features from specific instances or examples. A key mechanism in cognitive development, Piaget’s idea of reflective abstraction is a process by which new ideas and capabilities are created as a result of generalizations of what was found to be common across a range of instances.
The process of breaking a concept or problem down into simpler parts, so that its logical structure is displayed. This involves giving rigorous attention to meaning, logic, and the structure of language, and can involve the application of formal analytical procedures, such as sentential calculus or mathematical modeling. [This should be in philosophy]
The process of integrating ideas, concepts, or skills into higher order wholes. Sometimes this is done through the reconciliation of thesis and antithesis, or through a unifying hierarchical integration of polarities, differences, and multiplicity. [This should be in philosophy]
Immediate understanding, knowledge, or awareness, derived neither from conscious perceptions nor from explicit reasoning. Having an immediate awareness of the truth of a proposition (“I just know it’s true”) is unjustified as compared to beliefs based on inquiry and evidence; but truth claims form a small part of intuitive psychological processes. For example, the Chomskyan notion of linguistic competence implies an intuitive knowledge of grammatical concepts, which a person can apply correctly while being unable to state the rules of application.
The production of ideas or objects that are both novel or original and worthwhile or appropriate. Creative actions are unique and unprecedented while also being useful, attractive, meaningful, or correct. According to some researchers, in order to qualify as “creative,” a process of production must also be heuristic or open-ended, rather that algorithmic or rule based.
A subjective state in which one is intensely immersed in skillful activity while experiencing a feeling of energized focus, full involvement, and enjoyment. The term was coined in the research of Mihály Csíkszentmihályi. This experience is sometimes referred to as “being in the zone”.
Synonymous with general cognitive ability or the global capacity of an individual to act purposefully, to think rationally, and to deal effectively with their environment. However, recent research suggests that notion of an IQ (single intelligence quotient) oversimplifies intelligence, which is in fact composed of various aspects, such as verbal intelligence, problem solving, spatial reasoning, etc.
A theory proposed by Howard Gardner, that intelligence is not unified, but rather multiple, consisting of a set of relatively independent intelligences, which evolved as a part of the human mind-brain, including: linguistic intelligence, mathematical intelligence, spatial intelligence, musical intelligence, kinesthetic intelligence, interpersonal intelligence, intrapersonal intelligence, and naturalist intelligence. More recent research has suggested the addition of spiritual intelligence and emotional intelligence. According to these views, different intelligences can develop at different rates in individuals, and thus a single measure like IQ neglects within person variability across multiple kinds of intelligence.
A fundamental factor of human intelligence corresponding to rapid, unstructured, non-verbal, in-the-moment reasoning and problem solving. Isolated via factor analysis when introduced by Raymond Cattell in 1971, it is contrasted with crystallized intelligence, which is programmatic, rule-based, and explicitly linguistic.
A person of exceptional intelligence or ability. First named and investigated by the Eugenicist Sir Francis Galton, who used social eminence as his criterion, more recent oversimplifications declare anyone with an IQ over 140 to be a genius. Recent trends in schooling label children with IQs over 135 as gifted, putting them in a special institutional category. However, considering the inadequacy of IQ measures and the theory of multiple intelligences, traditional ideas of genius must be problematized. Immanuel Kant defined a genius as one who is vehicle for the laws of nature and who thus evolves the natural universe itself through human action.
An individual with a multitude of expertise and a broad background and diversity of learning. Classic examples include, Thomas Jefferson, Leonardo Da Vinci, Buckminster Fuller, Nikola Tesla, and Gottfried Leibniz. Polymaths tend to begin their extensive educations when they are very young and often describe themselves as having passion or deep love of learning, invention, and philosophy.
A form of reasoning that focuses on the assumptions and presuppositions of a discourse, which takes nothing at face value, and requests evidence, explanation, and justification. In well functioning research programs critical thinking is applied consistently as an aspect of knowledge production. Proponents of critical thinking suggest that individuals can apply critical thinking in most major aspects of their lives, including politics, economics, and healthcare. Critical thinking is often contrasted with dogmatism, scientism, and relativism. It should not be confused with critical theory, which is the application of heterodox economics, philosophical ethics, and social theory in the critique of political and cultural injustices.
A form of thinking that characterizes problems and phenomena as dynamic and systemic wholes, as opposed to isolated parts or static variables. Systemic thinking is referred to as “post-formal” in cognitive developmental psychology, because it is a form of thought that goes beyond simple formal logic to include feedback loops, iterative learning cycles, and multivariate analyses. Systems thinking should not be confused with Systems Science, which is a broad trans-display field, although the former is a cognitive prerequisite for the latter.
A psychological function that enables planning, focus, memory, and task sequencing, broadly related to processes of self-regulation. Best thought of as a set of related cognitive processes – including attentional control, impulse control, working memory, and cognitive flexibility, as well as reasoning, problem solving, and planning. These provide what is necessary for the cognitive control of behavior and form a kind of supervisory attentional system that directs psychological life.
A mental act of willing or trying whose presence is sometimes taken as the difference between intentional and voluntary action and mere behavior. Also sometimes referred to as “will” or “will power,” the phenomenon has been studied since the earliest days of psychology, although there are competing hypotheses about its biological basis and psychodynamic aspects.
The ability to override in-the-moment action tendencies, desires, and habits in the interest of either short or longer-term values. Related to executive function, volition, and attention, impulse control is part of a set of cognitive capacities that enable focused and efficient forms of higher order-agency and problem solving.
Renouncing immediate reward or satisfaction in order to obtain a larger reward in the future. Related to impulse control and executive, but also to self identity, delayed gratification has been shown to be a predictor of a wide range of life outcomes, including success in education and in relationships.
The capacity to understand and enter into another person’s feelings and emotion or to experience something from the other person’s point of view. An essential component of moral consciousness, empathy has been shown to be a capacity that can be trained and increased, and has thus been the focus of recent efforts in peace and social justice oriented education.
A theory or framework that specifies a set of types, kinds, or system of similarities and differences, often involving both a theoretical doctrine of types as well as an instrument or method for classification according to type. Typologies in psychology include, personality typologies, such as the Myers-Briggs, or typologies based learning styles, etc. Typologies are also common in fields other than psychology, including biology, astrology, and medicine.
Cumulative change over time that is punctuated by the qualitative emergence of higher-level action, thought, and capacity. Psychological development has been shown to be a process in which the skills and capacities of one level are hierarchically integrated into new functional ensembles, marking the emergence of a new developmental level. This process according to which the capacities of one level are transcended but included in the capacities of the next takes place across all domains of human skill and thought. Developmental theories include Piaget, Gilligan, Wilber, and Fischer.
The capacity to disinterestedly observe one’s own thought, actions, and sense perceptions. Typically associated with meditative practices, such as Vipassana or Zen, witnessing is believed to be a trainable capacity for disengaging from, and then observing, the workings of one’s own mind. This capacity has been shown to increase emotional stability, lower stress, and decrease one’s subjective sense of pain.
States of Consciousness:
Relatively transient alterations of feeling, mood, and capability, such as those induced via meditation or intoxication. There is a tradition of research about states of consciousness in psychology that goes back to the days of William James, who tested the effects of both religious meditations and drugs. It is common to discuss the three broadest states as waking, dreaming, and deep sleep, as well as to correlate these to Beta, Alpha and Delta EEG waves respectively.
The ability to stay focused, alert, and emotionally engaged with others, especially in complex or charged contexts.
The quality of being lucid, which is a state of concentration, clarity of insight, heightened awareness, and calm. Often a result of practices such as meditation, lucidity can be cultivated and is essential for some forms of higher level cognition and ethics.
A psychological trait believed to account for an individual’s ability to survive and bounce back from extremely difficult situations, such as poverty, abuse, violence, or neglect. It has been studied recently in school and military contexts, but the underlying explanatory processes remain obscure. For example, studies have shown that the presence of only a single positive relationship in an individual’s life is a strong predictor of resilience, which suggests it may not be a trait of individuals, but of groups or subcultures.
Philosophy / Epistemology / Science
The transdisciplinary study of the abstract organization of complex phenomena, independent of their substance, type, or spatial or temporal scale of existence. Not properly a single theory, but an approach to complex structures that can be applied to particular physical, chemical, biological systems. System sciences investigate both the principles common to all complex systems and the (usually mathematical) models that can be used to describe them. The field can be traced back to Ludwig von Bertalanffy.
A property of systems that have a large number of components that interact simultaneously in a rich number of parallel ways, exhibit non-deterministic bifurcations in their dynamic trajectories, and are sensitive to initial conditions when in formative chaotic regimes. The recent sciences of complexity can be traced back through Kauffman and Wolfram to C.S. Peirce, who first suggest that the laws of nature themselves evolved out of complexity, and that the universe and its workings are better thought to be like a cloud than a clock.
The behavior of whole systems not able to be predicted or reduced to the behavior of their parts taken separately. Synergies concern the behavior of the integral, aggregate, or whole, and represent the coordinated behaviors of mutually interacting and affecting sub-actors. Synergies occur at every level of physical, biological, psychological, and cultural evolution, can be intentionally fostered, and are related to processes of emergence, complexity, and self-organization.
Self-organized dynamic systems exhibit global properties that the basic entities within them do not possess. These are called emergent properties and they are the result of various conditions that allow for emergence. All complex systems show tendencies toward emergence, which at times creates new and unprecedented structures and forms, usually emerging out of complex processes of self-organization. Occurring in both biological evolution and in individual human development, the genesis of emergent structures is a major focus of research in system sciences.
The spontaneous ordering tendencies sometimes observed in certain classes of complex systems, both artificial and natural. Also explored under the rubrics or “emergent structuring,” “self-assembly,” and “autopoiesis,” these processes occur in an extremely wide range of systems and are implicated a variety of specific sciences. Examples of self-organizing processes in nature include everything from dust devils to cyclones and many forms of chemical and biological processes. First formally researched as Ilya Prigogine’s dissipative structures, which obey the second law of thermodynamics precisely by building structures that increase the entropy of their surroundings while decreasing it within their own boundaries.
The maintenance of equilibrium in any physiological, psychological, or social process by an automatic feedback mechanism compensating for disruptive changes. Complex dynamical systems often tend toward states of homeostasis and include feedback-loops and learning cycles that allow for self-regulation towards a steady state.
The process by which the organic world, including our own species, has been the product of a long, slow, natural process of development from forms very different, extremely simple, and probably themselves the result of natural processes that turned the inorganic into the living. The idea goes back to ancient Greece, and there have been many causal theories of evolution, but Darwin’s remains by far the most well known. Some philosophers—notably the American pragmatists—have thought that evolution must be one of the basic starting points of any attempts to understand human belief and action.
The practice of reducing complex phenomena into simpler and more fundamental parts usually for the purpose of making the phenomena easier to study. As a philosophical view, reductionism has played a major role in many scientific discoveries such as Newton’s theory of gravity and Maxwell’s theory of electrodynamics. Many complex phenomena, however, are more than just the sum of their parts and attempts to reduce them creates incorrect results. The early success of reductionism in elucidating basic scientific principles has created a bias in the scientific community toward this approach which has led to a systematic misunderstanding of interconnected complex phenomena.
In experimental and quasi-experimental research design variable isolation requires setting up controls. Isolating specific variables by altering conditions accordingly can assure the elimination of alternative explanations and center in on the variable that is of interest.
A science of communication and control systems, brought to prominence in the work of Norbert Wiener. Cybernetics concerns the communication and manipulation of information in service of guiding biological, physical, or chemical systems. Cybernetics has been deeply intertwined with mathematical theories of information and computation. The ideas of positive feedback loops and negative feedback loops can be traced to some of the earliest work in this field, which has undergirded computer science, cognitive science, and aspects of biology and chemistry.
In any hierarchically structured system recalibrations and changes can issue from lower-level changes that are propagated upward, as functionally interconnected units re-organize those higher-level processes in which they are involved. For example, when a person eats a meal, their digestive system works to provide nutrients that propagate upwards and ultimately provide energy and a sense of well being to the self. Bottom up action in hierarchical systems usually involves related processes of between level information exchange, upward causation, and distributed network-based learning.
In any hierarchically structured system recalibrations and changes can issue from higher-level nexuses of control, which functionally subsume diverse lower-level processes. For example, when a person chooses to cook a meal, their central nervous system exercises top down control over their appendages and sensorimotor schemas, to orchestrate the sequenced task of cooking. Top down action in hierarchical systems usually involves related processes of between level information exchange, downward causation, and feedback-based learning.
A term used to denote a class of problems in contemporary philosophy, such as the mind-body problem or the problem of free will, where the accepted experience of humanity appears to be at odds with certain emergent scientific hypothesis. Philosophy’s hard problems often point to the leading edge of science, ontology, and human self-understanding.
Often contrasted with objective when considering the source or justification of judgments. What is subjective concerns first-person experience, and often implies the unique or non-repeatable (although not always). What is objective, on the other hand, concerns the third-person perspective, and presumably verifiable and repeatable experiences (although not always). Phenomenology, meditation, and other forms of systematic observation of subjective experience have often been used to validate and make scientific claims about the subjective.
A pervasive feature of our mental lives and also possibly the most challenging source of problems in the whole of philosophy. This perplexity over something so familiar—the sense that there is something remarkable about consciousness—arises mainly as a result of modern questions about how it can be the product of physical and biological processes. The hard problems of mind-body interaction, qualia, and time-binding all arise from the persistence of consciousness as an obstacle to physicalism, behaviorism, and functionalism in the philosophy of mind and psychology. Non-Western traditions in philosophy have been less likely to locate consciousness solely in the human mind-brain and more likely to propose that consciousness is a basic aspect of the cosmos and an internal aspect of all life—a view known as panpsychism. Some recent views conversant with modern science, such as those of Whitehead, Chalmers, and Wilber, have proposed similar broadly metaphysical views of consciousness, arguing that it is a primordial aspect of the universe, like time, space, or matter. This reframes the hard problems, and re-position the human mind in the universe.
The act, process, or product of perceiving. Distinctions are common between sensation, the subjective experiences or feelings that result from excitation of the sense receptors, and perception, which is sensory experience that has been interpreted with reference to its presumed external stimulus or event. The smell of a rose may or may not mean the actual presence of a rose; excited sense receptors alone do not make for truth. Perceptions, on the other hand, are those sensations that have been reflectively integrated and made the subject of inferences and truth claims. Perceptions and reflective integrations of sense data are fundamental philosophical topics due to their central place in threis of of knowledge and of consciousness.
The qualitative, experiential, or felt properties of mental states. To know what it is like to have an experience is to know its qualia. The presence of qualia marks the difference between undergoing a series of events and experiencing a series of events. Some philosophers take qualia to be an essential feature of all conscious mental states; others only of sensations and perceptions. Either way the ontological status of qualia is at the center of the hard-problems of consciousness and mind-body interactionism. Qualia also figure prominently in the philosophy of language, phenomenology, and the cognitive neuroscience of perception.
The identity of a person as found in their subjective experience of a continuous personality or sense of “I-ness”. As a topic in philosophy the self has been taken to involve self-knowledge and self-reference, as well as experiences of embodiment, and intersubjectivity (there is no self unaware of itself, nor is there a self without a body or without other selves). G. H. Mead’s seminal theory of the self proposed at least two facets, the “I” or subjective witness and source of agency, and the “me” or socially constructed idea of the self, or “self thought”. “Me” or the distal self can be observed by the “I” or proximal self. This allows for a dialectic of self-development and the emergence of post-conventional forms of self-identity.
The central problem of agency concerns the difference between events that happen and events that are the result of intentional human action. Put another way, actions consist of things an agent does, not those things that happen to an agent (or even that happen within the mind or body of an agent). Actions are mediated and initiated by beliefs and ideas. This means they are to be understood differently from events, which occur due to causes, but are not intended or preconceived. Philosophers sometimes describe this in terms of the difference between event-causation and agent-causation, where the latter is not reducible to explanations of the former. Issues around theories of agency include classic problems of free will and determinism, the ontological status of agents, and the role of agent causation in the evolution of the universe.
The subfield of applied ethics that concerns issues arising in medicine and from advances in the biological sciences and biotechnologies. These include problems of the nature or and distribution of treatment, the sphere of authority of the patient, the range and structure of acceptable experimentation, and the limits of self-instrumentalization. Bioethics also addresses issues related to genetics, cloning, and biotech based forms of human augmentation and enhancement generally.
Neurohacking is the manipulation of, or the intervention on the nervous system with the goal of improving or repairing it. Neurohacking aims at optimizing brain function and structure, cognitive abilities and mental health, as well as preventing disease or recovering from injury.
A nootropic is a substance that can enhance one or more aspects of cognitive function, such as memory, learning, attention or motivation, for example. It can be a functional food, a nutraceutical, a supplement, or a drug.
Racetams are a class of synthetic compounds that share a structure called a pyrrolidone nucleus. Racetams may work by increasing the activation of cholinergic receptors that are colocalized with AMPA glutamate receptors, through an increased activation of the latter. Many racetams have nootropic actions.
Ampakines are a class of compounds that activate AMPA glutamate receptors. Ampakines can have nootropic actions such as the enhancement of attention, alertness, learning and memory.
Smart drugs are compounds that enhance cognitive function by potentially improving memory, learning abilities, reasoning, and decision making, by increasing attention, concentration, and problem solving skills, or by decreasing depression or anxiety. Smart drugs may work by boosting metabolism or blood flow to the brain, by preventing degenerative changes and damage, or by interacting with neurotransmitters or neuronal mechanisms and pathways.
A stack is a combination of two or more compounds with the goal of enhancing their benefits. Stacking can lead to a synergistic effect, with different compounds becoming more effective when taken in combination than when taken separately. Stacking may also allow for different effects to combine in order to obtain an amplified overall effect.