Brodmann area 4
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Caption = Brodmann area 4 of human brain. |
Image2 = Gray726-Brodman.svg |
Caption2 = Lateral surface. |
IsPartOf = [[Precentral gyrus]]|
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'''Brodmann area 4''' comprises the [[primary motor cortex]] of the human [[brain]].
Brodmann area 4 is about the same as the [[precentral gyrus]]. The borders of this area are: the [[precentral sulcus]] in front ([[anterior]]ly), the [[medial longitudinal fissure]] at the top ([[medial]]ly), the [[central sulcus]] in back ([[posterior]]ly), and the [[lateral sulcus]] along the bottom ([[Human anatomical terms#Anatomical directions|lateral]]ly).
This area of cortex, as shown by [[Wilder Penfield]] and others, has the pattern of a [[homunculus]]. That is, the legs and trunk fold over the midline; the arms and hands are along the middle of the area shown here; and the face is near the bottom of the figure. Because Brodmann area 4 is in the same general location as [[primary motor cortex]], the [[homunculus]] here is called the [[motor homunculus]].
The term '''area 4 of Brodmann-1909''' refers to a [[cytoarchitecture|cytoarchitecturally]] defined portion of the [[frontal lobe]] of the [[guenon]]. It is located predominantly in the [[precentral gyrus]]. [[Brodmann]]-1909 regarded it as topographically and cytoarchitecturally homologous to the human gigantopyramidal area 4 and noted that it occupies a much greater fraction of the frontal lobe in the monkey than in the human. Distinctive features (Brodmann-1905): the cortex is unusually thick; the layers are not distinct; the cells are relatively sparsely distributed; [[pyramidal cell|giant pyramidal (Betz) cell]]s are present in the internal [[pyramidal layer]] (V); lack of an internal [[granular layer]] (IV) such that the boundary between the external pyramidal layer (III) and the internal pyramidal layer (V) is indistinct; lack of a distinct external granular layer (II); a gradual transition from the [[multiform layer]] (VI) to the subcortical [[white matter]].
==See also==
* [[Brodmann area]]
* [[List of regions in the human brain]]
{{neuroanatomy-stub}}
{{Prosencephalon}}
[[Category:Brodmann areas|04]]