Luria "Neuropsychological studies in the USSR" Perception

op cit. still part I. Neuropsychology of perception

Luria stresses perception depends not just on afferents to primary visual cortex,but on selection of decisive cues about which objects seen are significant. Perception depends greatly on inputs from secondary visual areas, parietal and frontal inputs that are important for visual coding. Searching activities are crucial in formation of visual images in children. Sechenov is cited as showing ocular movements play a role similar to the searching movements of the hand.

Hubel and Wiesel showed the primary visual zone has neurons responsive to specific pieces of visual information such as shape, brightness, etc. Lesions lead to spatial disorganization of perceptions. Lesions of secondary areas lead to ability only to see separate details of an perceived object that Luria calls "amorphosynthesis" wherein they see only separate details of the image but can'tsynthesize it into a whole. The amount of "visual noise " in the background can affect perception. Lesions of the tertiary zones (occipito-parietal) cause Balint's syndrome involving simultanagnosia and impaired searching in space. Lesions of posterior eye fields lead to problems in passive eye searching, and lesions of the anterior premotor eye fields lead to problems in active eye searching.