Cerebral Cortex Functional Areas

Expansion

• Frontal: primary motor cortex (precentral gyrus), premotor and supplementary motor areas, Broca area (dominant inferior frontal gyrus), frontal eye fields, and prefrontal cortex for executive function, personality and inhibition
• Parietal: primary somatosensory cortex (postcentral gyrus), plus association areas. Dominant lesions give Gerstmann syndrome; non-dominant lesions give neglect and dressing or constructional apraxia
• Temporal: primary auditory cortex, Wernicke area (dominant), hippocampus for memory, and the inferior optic radiation
• Occipital: primary visual cortex, with macular sparing in posterior cerebral artery infarction because of dual blood supply

The homunculus explains the pattern of weakness: the medial surface represents the leg (anterior cerebral artery territory) and the lateral convexity the face and arm (middle cerebral artery territory).

Dysphasia: Broca gives non-fluent speech with preserved comprehension and awareness of the deficit; Wernicke gives fluent but meaningless speech with impaired comprehension; conduction aphasia, from arcuate fasciculus damage, impairs repetition selectively.