Includes two large, oval “cerebral hemispheres” that superficially resemble the surface of a shelled walnut. (Patestas, 69) Each cerebral hemisphere is subdivided into four “lobes.” (Ramachandran, 19) Makes up the “frontal lobe,”  “parietal lobe,”  “temporal lobe,” and “occipital lobe.” (Patestas, 399) Includes 50-100 billion nerve cell bodies arranged into a three to six-layered sheet. (Patestas, 399) Not a smooth sheet, but rather has numerous 'infoldings' or crevices. Bumps or ridges of cortex … rise up between the crevices. (Blumenfeld, 24) In humans, the cortex has grown so large that it has been forced to become convoluted. The cortex of most other mammals is smooth and flat for the most part, with few if any folds in the surface. (RamachandranTTB, 17) The folding occurs during development. Folded to facilitate its accommodation in the limited space available in the ‘cranial vault.’ (Patestas, 399) Not fully developed until about the third or fourth year, around the time that children start laying down permanent “memories.” (Foer, 84) If the cerebral cortex of a normal human brain were spread out, the cortex would extend over 2.5 square feet. Thickness varies from 1.5mm in the primary “sensory” areas to 4.5mm in the “motor” and “association” areas. (Patestas, 399) Surprisingly populated by only three kinds of neurons: “pyramidal cells,”  “fusiform cells,” and “granule cells.” (Patestas 400) Functionally organized into regions that specialize in different tasks – i.e. vision, hearing, touch, and movement. (Blakeslee, 41) The idea that different regions of the brain are specialized for different purposes is central to modern brain science. (Kandel, 123) Primary regions (are) responsible for deciphering inputs from "sensory receptors" and for executing movements. These regions together occupy about a third of the (cerebral cortex). The remaining, located in the frontal, temporal, and parietal lobes, is referred to as “association cortex.” (Kolb, 527) Because of the complexity of the (cerebral) cortex, scientists divide it into smaller and smaller parts and analyze those, hoping that such a reduction will ultimately lead to an understanding of the whole. (Koch, 117) Also referred to “cortex,"  'neocortex,'  ‘isocortex,’  ‘neopallium,’ and ‘cerebral mantle.’


Back of the Cortex: shorthand for all cortical regions that lie behind the "central sulcus," including all purely sensory regions - with the notable exception of “olfaction.” (Koch, 330)

Cerebral Cortex Layers: six cell layers labeled I through VI, counting from the surface inward. Layer I contains mainly “dendrites” of neurons from deeper layers as well as “axons.” Layer II and Layer III contain neurons that project mainly to other areas of cortex. Layer IV receives the majority of inputs from the “thalamus.” Layer V projects mostly to “subcortical” structures other than the thalamus, such as the “brainstem,” “spinal cord,” and “basal ganglia.” Layer VI projects primarily to the thalamus. In addition to these connections, numerous other circuits exist between and within the cortical layers. (Blumenfeld, 30) Also referred to as ‘layers.’

Cerebral Hemispheres: if the brain is split right down the middle into two halves, each half is called a 'hemisphere' and referred to as either the “right hemisphere” or the “left hemisphere.” Both hemispheres match each other. They have identical parts. Each hemisphere is grouped into four different chunks or parts called lobes. (Great Brain, 45) One side of the cerebral cortex. (Also refers to) one side of the “cerebellum” (which is not a part of the cerebral cortex.) (Kolb, 5) Each hemisphere controls the movements of the muscles on the opposite side of your body. The two hemispheres are specialized for different mental capacities. The most striking asymmetry involves language. (Ramachandran, 131) Also referred to as ‘hemispheres.’

Left Hemisphere: specialized not only for the actual production of speech sounds but also for the imposition of (the “syntax”) structure on speech and for "semantics." (Ramachandran, 133) The left hemisphere is better at dealing with familiar information than the right hemisphere. (Goldberg, 32)  More rational than the “right hemisphere.” People who suffer damage here are often anxious, depressed or worried about their prospects for recovery. The reason seems to be that with the left brain injured, their right brain takes over and frets about everything. (Ramachandran, 13)

Right Hemisphere: involved in recognizing faces and determining if they are new. (Goldberg, 26) The right hemisphere is better at dealing with novel, unfamiliar information than the left. (Goldberg, 32) Seems to be involved in more subtle aspects of language such as nuances of “metaphor”, “allegory”, and “ambiguity.” Concerned with holistic aspects of vision such as ‘seeing the forest for the trees,’ reading facial expressions, and responding with the appropriate “emotion” to evocative situations. (Ramachandran, 133) Tends to be more emotionally volatile than the left. People who suffer damage here tend to be blissfully indifferent to their own predicament. (Ramachandran, 13)

Cortical: adjective referring to “cortex.”

Cortical Column: large bundle of ascending or descending nerve fibers. (Patestas, 4) Neurons in the occipital lobe are organized in columns, where each neuron in a column has similar "receptive fields." (Chudler, 47) A design feature of the cortex. Neurons are not haphazardly arranged within the brain, but assemble according to orderly principles that neuroscientists are uncovering bit by bit. Most neurons found within a column, extending perpendicular to the ‘cortical sheet' from top to bottom over a distance of a few millimeters, have one or more features in common. For example, neurons stacked above each other in “V1” are active in the orientation of visual stimuli. Neurons stacked above each other in an area called "MT" are active in one particular direction of movement. (Koch, 28)

Gyrus: bulge on the surface of the cortex. (Carter, 15) The bumps on the cerebral cortex. They ‘demarcate’ functional zones. (Kolb, 5) The (cerebral) cortex forming the gyri dips down into the pit of the adjacent “sulci” to line them. Certain gyri and (sulci) are similar in all normal human brains. Others, may vary in different brains. (Patestas, 399) Plural - ‘gyri.’

Subcortical: adjective referring to brain regions below or underneath the (cerebral cortex). Somatosensory patterns travel through a set of subcortical areas that are unique to somatic senses. Hearing relies on a set of audition-specific subcortical structures that process auditory patterns before they reach the (cerebral cortex). (Hawkins, 198) A number of subcortical structures exist in the brain. In the ancient brain two sets of structures could be identified: the “thalamus” and the “basil ganglia.” (Goldberg2, 30) Also referred to as ‘old cortical regions.’

Sulcus (Sulci): the grooves on the outside surface of the brain. (Chudler, 25) Each infold on the surface of the (cerebral) cortex. (Blakeslee, 20) The groves of the cerebral cortex. Demarcate functional zones. (Kolb, 5) Shallow, short groves. Approximately two-thirds of the brain’s surface lies within 'sulcal valleys.' (Fisch, 276) Plural - ‘sulci.’ Adjective - ‘sulcal.’

Calcarine Sulcus: posteriorly, it divides the "occipital lobe" into two gyri. (Fisch, 282) Divides the “cuneus” from the “lingula.” (Blumenfeld, 25-26) Does not affect the “ventricular system.” (Fisch, 276) Also referred to as ‘calcarine fissure.’

Callosal Sulcus: runs along the dorsal surface of the “corpus callosum.” (Fisch, 282)

Central Sulcus: large (sulcus) separating the front and back of the (cerebral cortex). (Hawkins, 103) The division between the “frontal” and “parietal lobes.” (Fisch, 280) The central sulcus and the “silvian fissure” form the boundaries of each frontal lobe. They also form the boundaries of each parietal lobe. (Kolb, 53) The region surrounding it is called the “paracentral lobule.” (Blumenfeld 25) Also referred to as the ‘central fissure' and the 'central sulcus of Rolando.’

Cingulate Sulcus: boundary of the “limbic lobe.” Located above and parallel to the corpus callosum. (Fisch, 280)

Circular Sulcus: completely circumscribes the insula. (Patestas, 75)

Fissure: a deep sulci. (Kolb, 41) Extends through the entire cerebral wall and later the contour of the deep-lying ventricular system. (Fisch, 276) Editor's note - some authors make a distinction between a 'sulcus' and a 'fissure' describing a ‘sulcus’ as merely indenting the outer surface of the brain. Others use the terms interchangeably.

Frontal Sulci: editor's note - these primarily define the frontal lobe gyri.

Inferior Frontal Sulcus: divides the “inferior frontal gyrus” from the “middle frontal gyrus.” (Blumenfeld, 25)

Olfactory Sulcus: just inside the medial border of the frontal lobe. (Fisch, 284-285) Contains the “olfactory bulb” and separates the “orbital frontal gyri” from the “gyrus rectus.” (Blumenfeld, 25)

Paracentral Sulcus: divides the “superior frontal gyrus” and the “anterior paracentral gyrus.” (Fisch, 283)

Precentral Sulcus: “anterior” boundary of the “precentral gyrus.” Vertically oriented. (Fisch, 278)

Superior Frontal Sulcus: divides the superior frontal gyrus from the middle frontal gyrus. (Blumenfeld, 25)

Great Longitudinal Fissure: separates the two hemispheres of the brain. (Blumenfeld, 25) The floor of the 'longitudinal' is formed by the “corpus callosum.” (Patestas, 69) Also referred to as  ‘interhemispheric fissure,’ ‘longitudinal fissure,’ ’longitudinal cerebral fissure,'  ‘medial longitudinal fissure,’ and 'sagittal fissure.’

Marginal Cingulate Sulcus: marginal branch running up to the “superior” surface that forms an important landmark, since the sulcus immediately in front of it, on the superior surface, is the central sulcus. (Blumenfeld, 25)

Parietal Sulci: editor's note - these sulci primarily define the parietal lobe gyri.

Intraparietal Sulcus: divides the "inferior parietal lobule" from the “superior parietal lobule.” (Blumenfeld, 25)

Postcentral Sulcus: posterior boundary of the “postcentral gyrus.” Vertically oriented. (Fisch, 278)

Parieto-Occipital Sulcus: separates the parietal and occipital lobes. (Blumenfeld, 25) Also referred to as the ‘parieto-occipital-fissure.’

Preoccipital Notches: points on the surface of the brain used to draw an imaginary line to define the border between the occipital lobe and the (temporal) lobe. (Patestas, 70) For practical purposes, the division between the occipital and temporal lobes. No true boundary separates the temporal lobe from the occipital lobe. (Fisch, 280)

Sylvian Fissure: the (prominent) sulci at the side of the brain. (Kolb, 41) An especially deep sulcus. (Blumenfeld, 24) Demarcates each temporal lobe, forming its dorsal boundary. (Kolb, 53) The floor of the Sylvian fissure is formed by the insula. (Patestas, 70) Also referred to as the ‘lateral sulcus’  ‘lateral fissure,’ and ‘fissure of Sylvius.’

Anterior Horizontal Ramus: extension of the sylvian fissure, extending horizontally, divides the “pars orbitalis” and the “pars triangularis.” (Fisch, 286-287)

Ascending Ramus: extension of the sylvian fissure, extending vertically, divides the  “pars triangularis” and the “pars opercularis.” (Fisch, 286-287)

Temporal Sulci: editor's note - these sulci primarily define the temporal lobe gyri.

Collateral Sulcus: separates the “fusiform gyrus” from the “parahippocampal gyrus.” (Blumenfeld 25)

Inferior Temporal Sulcus: separates the “inferior temporal gyrus” from the fusiform gyrus. (Blumenfeld, 25-26)

Middle Temporal Sulcus: divides the “middle temporal gyrus” from the inferior temporal gyrus. (Blumenfeld, 25-26)  

Occipitotemporal Sulcus: located in the inferior (region) of the temporal lobe. Parallel to the collateral sulcus. (Fisch, 282)

Rhinal Sulcus: an “anterior” continuation of the collateral sulcus. (Blumenfeld, 25) Also referred to as ‘rhinal fissure.’

Superior Temporal Sulcus: divides the “superior temporal gyrus” from the middle temporal gyrus. (Blumenfeld, 25-26)

Topographical: characteristic of human sensory and motor “brain maps.” It means that areas adjacent to each other on the body’s surface are generally adjacent to each other on the brain maps. (Doidge, 49) Adjacent areas on the receptive surface are ‘mapped’ to adjacent fibers in “white matter”  pathways and to adjacent regions of cortex. For example, (the) “primary motor” and “primary somatosensory cortex” regions representing the hand, are adjacent to regions representing the arm. (Blumenfeld, 28) The discovery of the topographical representation of the “motor cortex” suggested how movement might be produced. Information from other regions of the (cerebral cortex) could be sent to the (motor cortex), and neurons in the appropriate part of the (motor cortex) could then execute the movements called for. (Kolb, 354)

Body Mandala: Sandra Blakeslee’s metaphor for one’s integrated network of brain maps. (Blakeslee, 213)

Brain Map: a map of your body’s surfaces located in the brain. Any scheme that spells out one-to-one correspondences between two different things. Located in your brain are complete maps of your body’s surface, with patches devoted to each finger, hand, cheek, lip, eyebrow, shoulder, hip, knee, and all the rest. (Blakeslee, 7-8) Dr. Walter Penfield in the 1930’s discovered the connection between body parts and the brain by touching parts of a patient’s brain with an electric probe and observing that it triggered sensations that the patient felt in his body. He created a map of where a sensation from each part of the body was felt in the brain. He called his map the “homunculus.” He also discovered that the brain map was topographical. V.S. Ramachandran and his team used “MEG” on amputees to demonstrate that brain maps can change, sometimes rapidly. (Ramachandran, 31) Michael Merzenich discovered that the maps were not universal, but could vary within their borders and vary in size from person to person. He discovered that a single person’s brain map frequently changes over the course of his life. He discovered that a person could effect changes to a brain map by changing his or her "behavior." (Doidge, 48-49) Far from signaling a specific location on the skin, each neuron in the map is in a state of dynamic “equilibrium” with other adjacent neurons; its significance depends strongly on what other neurons in the vicinity are doing, or not doing. (Ramachandran, 35)

Homunculus: complete brain map of the body’s surface made by Walter Penfield in the 1930’s. First ever map of a human being’s “somatosensory cortex.” (Blakeslee, 17) Draped across the surface of the cerebral cortex. (Ramachandran, 25)

Motor Homunculus: a brain map that sends signals out to one’s muscles and creates one’s ability to move and assume complex positions in space. (Blakeslee, 214) The majority of the motor homunculus lies along the “precentral gyrus,” but the leg dangles along the “anterior”  “paracentral gyrus.” (Fisch, 282) Also referred to as ‘primary motor map.’

Sensory Homunculus: a map of one’s body surface found in the “somatosensory cortex,” a brain region that receives touch sensations, such as pressure and vibration, from the skin (Blakeslee, 215) Also referred to as ‘primary touch map.’

Peripersonal Space Map: a map of the space surrounding the body. Physiological properties (of “mirror neurons”) suggest that this is a map of ‘potential actions’ performed by the body. (Iacoboni, 16) (Brain map of the) invisible volume of space around one’s body out to arm’s length. Through a special mapping procedure, the brain annexes this space to the limbs and body, clothing one in it like an extended, ghostly skin. (Blakeslee, 3)