Brodmann area 21
Encyclopedia
Brodmann area 21, or BA21, is part of the temporal
cortex
in the human brain
. The region encompasses most of the lateral temporal cortex, a region believed to play a part in auditory processing and language. Language function is left lateralized in most individuals. BA21 is superior to BA20
and inferior to BA40
and BA41.
This area is also known as middle temporal area 21. It is a subdivision of the cytoarchitecturally defined temporal region of cerebral cortex. In the human it corresponds approximately to the middle temporal gyrus
. It is bounded rostrally by the temporopolar area 38 (H), ventrally by the inferior temporal area 20, caudally by the occipitotemporal area 37 (H), and dorsally by the superior temporal area 22 (Brodmann-1909).
defined on the basis of cytoarchitecture. It is cytoarchitecturally homologous to the middle temporal area 21 of the human (Brodmann-1909). Distinctive features (Brodmann-1905): Compared to area 20 of Brodmann-1909, the total cortical thickness of area 21 is greater, the granular cells are less abundant, and the boundary with the subcortical white matter
is less distinct; the molecular layer (I) is wider; the pyramidal cell
s of sublayer 3b of the external pyramidal layer (III) are larger; the internal granular layer
(IV) is less developed and contains fewer cells; ganglion cell
s of the internal pyramidal layer (V) are larger, rounder, and densely arrayed adjacent to layer IV; the boundary between layer V and the multiform layer (VI) is indistinct; and layer VI is wider and has no sublayers.
Temporal lobe
The temporal lobe is a region of the cerebral cortex that is located beneath the Sylvian fissure on both cerebral hemispheres of the mammalian brain....
cortex
Cerebral cortex
The cerebral cortex is a sheet of neural tissue that is outermost to the cerebrum of the mammalian brain. It plays a key role in memory, attention, perceptual awareness, thought, language, and consciousness. It is constituted of up to six horizontal layers, each of which has a different...
in the human brain
Human brain
The human brain has the same general structure as the brains of other mammals, but is over three times larger than the brain of a typical mammal with an equivalent body size. Estimates for the number of neurons in the human brain range from 80 to 120 billion...
. The region encompasses most of the lateral temporal cortex, a region believed to play a part in auditory processing and language. Language function is left lateralized in most individuals. BA21 is superior to BA20
Brodmann area 20
-Human:Brodmann area 20, or BA20, is part of the temporal cortex in the human brain. The region encompasses most of the ventral temporal cortex, a region believed to play a part in high-level visual processing and recognition memory....
and inferior to BA40
Brodmann area 40
Brodmann area 40, or BA40, is part of the parietal cortex in the human brain. The inferior part of BA40 is in the area of the supramarginal gyrus, which lies at the posterior end of the lateral fissure, in the inferior lateral part of the parietal lobe....
and BA41.
This area is also known as middle temporal area 21. It is a subdivision of the cytoarchitecturally defined temporal region of cerebral cortex. In the human it corresponds approximately to the middle temporal gyrus
Middle temporal gyrus
Middle temporal gyrus is a gyrus in the brain on the Temporal lobe. It is located between the superior temporal gyrus and inferior temporal gyrus. Its exact function is unknown, but it has been connected with processes as different as contemplating distance, recognition of known faces, and...
. It is bounded rostrally by the temporopolar area 38 (H), ventrally by the inferior temporal area 20, caudally by the occipitotemporal area 37 (H), and dorsally by the superior temporal area 22 (Brodmann-1909).
Guenon
Brodmann area 21 is a subdivision of the cerebral cortex of the guenonGuenon
The guenons are the genus Cercopithecus of Old World monkeys. Not all the members of this genus have the word "guenon" in their common names, and because of changes in scientific classification, some monkeys in other genera may have common names that do include the word "guenon"...
defined on the basis of cytoarchitecture. It is cytoarchitecturally homologous to the middle temporal area 21 of the human (Brodmann-1909). Distinctive features (Brodmann-1905): Compared to area 20 of Brodmann-1909, the total cortical thickness of area 21 is greater, the granular cells are less abundant, and the boundary with the subcortical white matter
White matter
White matter is one of the two components of the central nervous system and consists mostly of myelinated axons. White matter tissue of the freshly cut brain appears pinkish white to the naked eye because myelin is composed largely of lipid tissue veined with capillaries. Its white color is due to...
is less distinct; the molecular layer (I) is wider; the pyramidal cell
Pyramidal cell
Pyramidal neurons are a type of neuron found in areas of the brain including cerebral cortex, the hippocampus, and in the amygdala. Pyramidal neurons are the primary excitation units of the mammalian prefrontal cortex and the corticospinal tract. Pyramidal neurons were first discovered and...
s of sublayer 3b of the external pyramidal layer (III) are larger; the internal granular layer
Granular layer
The term granular layer may refer to:*the granular layer of Tomes, seen in dentin of the teeth. When dry section of the root dentin of teeth are visualized under transmitted light, a granular layer is seen adjacent to cementum.It is believed to be caused by coalescing & looping of terminal portion...
(IV) is less developed and contains fewer cells; ganglion cell
Ganglion cell
A retinal ganglion cell is a type of neuron located near the inner surface of the retina of the eye. It receives visual information from photoreceptors via two intermediate neuron types: bipolar cells and amacrine cells...
s of the internal pyramidal layer (V) are larger, rounder, and densely arrayed adjacent to layer IV; the boundary between layer V and the multiform layer (VI) is indistinct; and layer VI is wider and has no sublayers.
External links
- For Neuroanatomy of the middle temporal area 21 visit BrainInfo
- For Neuroanatomy of Brodmann area 21 visit BrainInfo
See also
- Brodmann areaBrodmann areaA Brodmann area is a region of the cerebral cortex defined based on its cytoarchitectonics, or structure and organization of cells.-History:...
- List of regions in the human brain