- Cerebral Gray Matter 269
Cerebral Cytoarchitecture ( Advanced )
■ Th ree diff erent histologic patterns of cerebral
cortex exist: neocortex, allocortex, and mesocortex.
■ Neocortex (aka isocortex) is the phylogenetically
newest cortical cytoarchitecture and comprises six
layers.
■ Allocortex is phylogenetically older and comprises
from three to fi ve layers.
■ Mesocortex represents transitional cortex between
neocortex and allocortex.
■ A prominent example of a pyramidal cell are the
Betz cells, which lie primarily within the primary
motor cortex.
■ Th e six cytoarchitectural layers of the neocortex,
from outside to inside, are the molecular, external
granular, external pyramidal, internal granular layer,
internal pyramidal, and multiform layers.Brodmann Areas
■ Areas 3, 1, 2 lie within the postcentral and posterior
paracentral g yri; they constitute the primary sensory
area.
■ Area 4 lies within the precentral and anterior
paracentral g yri; it is the primary motor area.
■ Area 8 lies in front of area 6; it contains the human
homologue to the rhesus monkey frontal eye
fi elds.
■ Area 44 lies in the pars opercularis of the inferior
frontal g yrus and area 45 lies in the pars triangularis
of the inferior frontal g yrus; together, they make up
Broca’s area — the speech output area.
■ Areas 41 and 42 lie in the transverse temporal g yri
(Heschl’s g yri); they make up the primary auditory
cortex.
■ Area 22 lies in the superior temporal g yrus and,
posteriorly, it contains Wernicke’s area — the language
reception area.
■ Area 17 lies on the banks of the calcarine sulcus and
is the primary visual cortex.