Question

Why does the cerebral cortex have both visual cortex and a visual association center? What would be the result if the visual cortex was damaged but not the association center? what would be the result if the visual association center was damaged but not the visual cortex?

Answer 1

Cerebral cortex has visual cortex and visual association area both because of their functions. Primary visual area (Visual Cortex) is concerned with reception and perception of isolated visual impressions like colour , size, form, motion, illumination and transparency. It is just for seeing the object.

Secondary visual area (Visual Association Area) receives afferents from the visual cortex. It relates the information to the past experiences, thus enabling the individual to recognise and appreciate what he is seeing. In other words, this area is responsible for recognition of objects seen.

Damage of visual cortex:-

IT results in the loss of vision in the opposite visual field (crossed homonymous hemianopia). Peripheral vision is lost with normal macular vision called macular sparing. The unilateral lesions of the superior wall of post calcarine sulcus results in inferior quandrantopic hemianopia. Whereas lesion of Inferior wall of post calcarine sulcus results in superior quandrantopic hemianopia.  

Damage of Visual Association Area:-

The patient can see the object but cannot recognise. Loss of ability to recognise objects (VISUAL AGNOSIA) seen in the opposite field of vision.