Neuron Types: Galen, a second century Greek Physician, experimented widely on nerves and gradually developed the idea that nerves can either return information to the brain from the organs of sight, sound, smell, taste, or touch, or transmit impulses to the muscles to make them contract. We now use the terms "sensory" and "motor" to distinguish these two types. (Bainbridge, 26)
Throughout the twentieth century, localizationists would proceed to divide the cerebral cortex into visual, auditory, tactile, motor, olfactory, and gustatory centers. Soon, individual neurons were being labeled as visual neurons, “mirror neurons,” “face neurons,” touch neurons, even ‘grandmother neurons.’ (Nicolelis, 46) Neurons, as far as one can fathom, are unique cells, of a kind unlike any other in the body, unlike even other kinds of brain cells. (Damasio, 37)
Functional Neurons: editor's note - includes neurons grouped by the brain function they support.
Interneurons: one of the three major functional types of neurons. These connect or regulate other neurons. Many interneurons are “inhibitory.” (Kandel, 440) They send (link) their short “axons” to nearby neurons. One of their main jobs is to regulate the flow of (information) by controlling the activity of neurons. (LeDoux, 50) Also referred to as ‘local circuit cells.”
Cells of Martinotti: “multipolar” interneurons displaying short dendrites. Most populous in the deepest cortical layer. Their axons, which give rise to several “collateral” branches, course toward the surface of the cortex. (Patestas, 402)
Motor Neurons: an “efferent neuron” that sends impulses from the “central nervous system” to skeletal muscles. (NCIt) Provide output from the cerebral cortex. (Patestas, 404) Transmit impulses to the muscles to make them contract. (Bainbridge, 26) (They) form “synapses” with muscle cells, convey information from the central nervous system and convert it into movement. (Kandel, 442) Motor cells fire throughout the whole (hand) grasping action, and not in correspondence with the contractions of any specific muscles. The same cell often fires for both right-hand and left-hand actions. (Iacoboni, 23) Also referred to as ‘motoneuron.'
Command Cell: a single cell that can control an entire behavioral sequence. (The Brain-Eric Kandel, 31)
Lower Motor Neurons (LMNs): located in the anterior “horns” of the central “gray matter” of the “spinal cord.” The axons of LMNs project out of the central nervous system … to finally reach muscle cells in the periphery. (Blumenfeld, 33) A LMN “lesion” results in paralysis and severe “atrophy” and “fasciculations” in the ‘denervated’ (no longer connected by a nerve) muscle(s). (Patestas, 187)
Upper Motor Neurons (UMNs): those projecting from the cortex down to the spinal cord or “brain stem.” They form synapses onto the lower motor neurons. (Blumenfeld, 33) The most prominent physical deficit from damage is paralysis of the upper and lower limbs. (Patestas, 187)
Sensory Neurons: neurons which convey sensory information centrally from the periphery. (MeSH) Provide input to the cerebral cortex. (Patestas, 404) Return information to the brain from the organs of sight, sound, smell, taste, or touch. (Bainbridge, 26) Translate different kinds of information from the external world into electrical patterns that are sent down our neurons. (Doidge, 18) Transmit information about environmental stimuli from a “sensory receptor” neuron to other sensory neurons in a sensory “pathway.” Specialized to respond to a particular physical property, such as touch, light, or temperature. (Kandel, 447-448) Also referred to as a ‘receptor neurons’ and ‘perception neurons.’
Face Cells: part of the network of cells involved in the recognition of faces and other objects. (Ramachandran, 78) Also referred to as ‘face neurons.'
Flinch Cells: these neurons fire when objects approach the face or body. Used to thwart threats within personal space (Blakeslee, 134)
Grid Cells: neurons related to place cells that map space in terms of an imaginary triangular lattice, without regard to landmarks or other features of the environment. (Blakeslee, 213) The very best athletes have spectacular grid cells. When you move through space, grid cells mark your position. Discovered in 2005. (Blakeslee, 132)
Mirror Neurons: first described by Giacomo Rizzolatti and his research team in 1994. Represent actions performed both by oneself and by another. They are the key to many higher mental functions including imitation, empathy, and the ability to read others intensions. (Blakeslee, 164, 213) Fire not only when you perform an action, but also when you watch someone else perform the same action. (RamachandranTTB, 22) Fire when an individual kicks a soccer ball, sees a ball being kicked, hears a ball being kicked, and even just says or hears the word ‘kick.’ (Iacoboni, 12) (A human) cannot observe someone else picking up an apple without also invoking in the brain the motor plans necessary to snatch that apple themselves. (Iacoboni, 14) Sense the move another person is about to make and sense their feelings. Instantaneously prepare us to imitate that movement and prepare us to feel with them. (Goleman, 9) May well be central to social learning, imitation, and the cultural transmission of skills and attitudes. (RamachandranTTB, 23)
Pain Neurons: (their) cell bodies are round crystalline globe-like, gel-filled balloons. Have no dendrites. Axon extends from each balloon and passes, bundled together with (axons) from other sense neurons, through our nerves to reach the skin or muscle somewhere on our bodies. Here (their) tiny nerve endings fray apart and become specialized into microscopic sensory organs that can sense touch, pressure, heat, cold, irritating chemicals, and substances released by skin cells damaged by sunburn, abrasion, or cuts. Pain neurons are not located in the brain. Not located in the "spinal cord" either. (They are located) between each "vertebrae" of the bony "spinal column." In the space between each bone there is a sack of pain neurons. One sack of pain neurons on each side of the spinal column. (Fields, 186-187)
Place Cells: "hippocampal" neuron that fires when an animal is in a certain location in an environment. (Kolb, 467) When an animal moves to a different location, different place cells become active. (Kandel, 445) Neurons related to grid cells that map space with reference to landmarks and other features of the environment. (Blakeslee, 214) For example, there are place cells which represent the specific location of each object in a room. (Blakeslee, 130) Place cells create an enduring spatial map only when an organism focuses its spotlight of “attention” on its surrounds. (Best of the Brain-Eric Kandel, 71)
Retinal Neurons: neurons found in the “retina” of the eye. One census identified about five dozen distinct cell types, each one probably serving a distinct function. (Koch, 49) “Photoreceptors” in the retina are connected to two layers of retinal neurons. (Kolb, 278) Also referred to as ‘retinal cells.’
Retinal Ganglion Cells: neural cells of the retina that give rise to the “optic nerve.” The axons of the ganglion cells collect in a bundle at the "optic disc" and leave the eye to form the optic nerve. (Kolb, 278)
Magnocellular Cells (M-Cells): large-celled visual-system neuron that is sensitive to moving stimuli. Receive their input primarily from “rods” and so are sensitive to light but not to color. (Kolb, 278)
Parvocellular Cells (P-Cells): small-celled visual-system neuron that is sensitive to form and color differences. Receive their input primarily from “cones” and so are sensitive to color. (Kolb, 278)
Von Economo Neuron: first observed by Von Economo in 1925. Located in the “ACC” and frontal "insulas” – especially the “right frontal insula.” A special class of neurons found in the cortex of only the most mentally and emotionally advanced mammals. These cells play a key role in the ability to achieve fast, intuitive judgments and insights. Contain receptors for chemicals involved in social bonds, in the expectation of "reward," and in those used for detecting danger. (Blakeslee, 187, 215) Also referred to as ‘Von Economo cells’ and “intuition cells.
Messenger Neurons: editor's note - includes neurons grouped by the type of neurotransmitter sent or received.
Cholinergic Neuron: a neuron that responds to “acetylcholine.” Localized both in the central and the peripheral nervous systems. (Patestas, 49)
Dopaminergic Neuron: a neuron that responds to “dopamine.” Includes neurons of the “arcurate nucleus” whose axons project to the ‘hypophysis,” the “ventral tegmental area” whose axons project to the “limbic system,” and the “substantia nigra” whose axons project to the “striatum.” (Patestas, 47)
Hypothalamic Neurosecretory Cells: have both the “morphological” characteristics of neurons and, upon stimulation, transmit nerve impulses down their axons. In addition, these cells also have “endocrine” properties since they produce “hormones” that are released into the bloodstream. This process is referred to as "neurohypophysis." (Patestas, 378)
Oxytocin Magnocellular Neurons: specialized neurons in the “hypothalamus” that make “oxytocin.” Send (link) their axons from the hypothalamus into part of the “pituitary,” where they release their contents into the space around “capillaries.” The capillaries then absorb the oxytocin into the bloodstream and distribute it throughout the body. (Fields, 257)
Vasopressin Magnocellular Neuron: like oxytocin, "vasopressin" becomes bound to a "carrier protein" and is then transported within "vesicles" down the axons to the "axon terminal" located in the pituitary gland. The hormone is either stored or released and then passes into the blood circulation. (Patestas, 378)
Noradrenergic Neuron: a neuron that responds to "norepinephrine." Located in sympathetic (nervous system) neurons. (Patestas, 48)
Serotonergic Neuron: neurons that use “serotonin” as their neurotransmitter substance. They are present in the “pons.” “medulla,” “midbrain,” and ”pineal body.” (Patestas, 48)
Neurons by Shape: editor's note - includes neurons grouped by the characteristics of their structure.
Bipolar Neurons: a nerve cell with two processes. (NCIt) Retain their two processes at opposing poles of the cell body. Dendrites of these cells collection information from the periphery of the body, whereas their axons deliver information to the central nervous system for processing. (Kolb, 19)
Fusiform Cells: reside in the deepest cortical layer. Dendrites project toward the cortical surface. Axons from fusiform cells project mainly to the “thalamus.” (Patestas, 400)
Granule Cells: small cells whose dendrites radiate from their cell body in all planes. Have a star-shaped appearance. Have a short axon which projects locally, in the cerebral cortex. Located in all cortical layers except Layer I. (Patestas, 400) Principle neurons of the “dentate gyrus.” (Blumenfeld, 830) Also referred to as ‘stellate cells.’
Aspiny Cells: do not have spines on their dendrites. Believed to be “inhibitory” interneurons since they utilize “GABA.” (Patestas, 401)
Spiny Cells: have spines on their dendrites. Located mostly in layer IV of the cerebral cortex. Believed to be “excitatory” interneurons, which release “glutamate.” (Patestas, 401)
Horizontal Cells: spindle-shaped cells, located only in Layer I of the cerebral cortex. Give rise to a dendrite and an axon, both of which remain in the superficial layer of the cortex. Their axons run horizontally, oriented parallel to the cortical surface. Synapse with “pyramidal cell” dendrites in this layer. Seldom seen in adult brains. (Patestas, 401) Also referred to as ‘horizontal cells of Cajal.’
Midget Neuron: has small compact dendrite trees. Serves as a conduit for “signaling” fine image details. (Koch, 59-60)
Multipolar Neuron: a nerve cell with several "processes," usually an axon and three or more dendrites. (NCIt) Collections of axons of multipolar neurons of the (neural tube) grow (and join with unipolar neurons) to form the “ventral roots” of the “spinal cord.” (Patestas, 19)
Parasol Neuron: possesses large dendrite trees. Collects information from many “cones” (Koch, 59-60)
Pyramidal Cells: a type of neuron found in the cerebral cortex, with a pyramid-shaped cell body, a branched dendrite expending from the apex towards the brain surface, several dendrites extending horizontally from the base, and an axon running in the white matter of the hemisphere. (OxfordMed) The main “output” neurons of the cerebral cortex. (Patestas, 400) Principal neurons of the hippocampus and the “subiculum.” (Blumenfeld, 830) A typically excitatory neuron found in the cerebral cortex. These cells receive and process the information coming into the hippocampus and send it on to the next relay point. The axons of these neurons are bundled into a pathway (called the "fornix") that leads out of the hippocampus. (Kandel, 139) Pyramidal cells play a critical role in an animal's perception of its spatial environment. (Kandel, 281) Also referred to as ‘pyramidal neurons.’
Spindle Cells: newly discovered class of neurons. (Goleman, 9) Shaped like a spindle, with a large bulb at one end and a long, thick extension. Suspected to be the secret of the speed of social intuition. The body is about four times larger than other neurons. Since the velocity of a neuron’s transmission to other neurons increases with the length of its dendrites and axon, the spindle’s ‘gargantuan’ dimensions ensure extremely high-velocity transmission. (Goleman, 66)
Unipolar Neuron: a conducting cell of the nervous system... It is always a sensory neuron. (NCIt) The two processes of each of these cells begin to grow toward and fuse with one another, forming a single process. This unified process then divides into two processes that grow in opposing directions. One enters the dorsal horn of the spinal cord where it may terminate or ascend to higher levels. Collections of these form the dorsal roots of the spinal nerve. Collections (of the other) join the ventral root fibers. (Patestas, 19) Also referred to as ‘pseudounipolar neuron.’