Visual Association Areas

Extrastriate areas V2 and V3 surround V1 above and below the calcarine sulcus. Isolated and clinically apparent lesions of V2 and V3 are unusual, but a combined lesion of V2 and V3 restricted to upper or lower bank typically causes a homonymous quadrantic visual field defect. y

Higher cortical processing of visual information occurs in visual association areas, which are divided anatomically and functionally into ventral and dorsal pathways. In general, the ventral stream (occipitotemporal) is more concerned with object recognition ("what") and represents the continuation of the parvocellular pathway. [10] Area V4, which is situated in the lingual and fusiform gyri, is responsible for color perception within the contralateral hemifield. y Bilateral mesial occipitotemporal regions are necessary for object and facial recognition. y y y In contrast, the dorsal stream carries out functions related to spatial orientation y (the "where" pathway) and is the extension of the magnocellular pathway. The parietal lobe is devoted to directed attention. Evidence suggests that Brodmann area 39, within the lateral occipitotemporal region, is analogous to monkey area MT and is important for motion perception.

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