Brodmann area 9

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Brain: Brodmann area 9
Brodmann area 9.png
Brodmann Cytoarchitectonics 9.png
Latin Area frontalis granularis
NeuroLex ID birnlex_1740

Brodmann area 9, or BA9, is part of the frontal cortex in the brain of humans and other primates. It contributes to the dorsolateral and medial prefrontal cortex.


The term Brodmann area 9 refers to a cytoarchitecturally defined portion of the frontal lobe of the guenon. Brodmann-1909 regarded it on the whole as topographically and cytoarchitecturally homologous to the granular frontal area 9 and frontopolar area 10 in the human. Distinctive features (Brodmann-1905): Unlike Brodmann area 6-1909, area 9 has a distinct internal granular layer (IV); unlike Brodmann area 6 or Brodmann area 8-1909, its internal pyramidal layer (V) is divisible into two sublayers, an outer layer 5a of densely distributed medium-size ganglion cells that partially merges with layer IV, and an inner, clearer, cell-poor layer 5b; the pyramidal cells of sublayer 3b of the external pyramidal layer (III) are smaller and sparser in distribution; the external granular layer (II) is narrow, with small numbers of sparsely distributed granule cells.[1]


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