Primary Cortex

Synonyms

Agranular (motor cortex); Granular or koniocortex (sensory cortex); Idiotypic cortex

Definition

Those areas of neocortex that either receive direct projections from the specific sensory relay nuclei of the thalamus (primary sensory cortex) or represent the final common pathway for motor fibers (primary motor cortex) prior to their entering the corticobulbar and corticospinal tracts of the internal capsule. The primary sensory cortices include Brodmann’s areas 3, 1 and 2 (somatosensory) in the postcentral gyrus of the parietal lobe, area 41 (auditory) dorsal portion of the superior temporal gyrus within the temporal operculum, and area 17 (visual) on the upper and lower banks of the calcarine fissure on the medial aspect of the occipital lobe. The primary motor cortex (Brodmann’s area 4) is located in the precentral gyrus of the frontal lobe. Although all are considered “primary” cortices, only unilateral lesions of the primary visual cortex will result in a complete loss of...