Luria on perception

Isomorphism, as introduced by the Gestalts such as Kohler, believe that during perception, a passive imprint on the retina is then transmitted to the cortex. More recent views of perception regard it as an active, complex process, involving perception, analysis, coding, synthesis, active inspection.

Luria notes a visual image stays on the retina for 1.5 seconds, with an afterimage lasting about 20 seconds (Working Brain p. 232). In patients with damaged occipital areas, the after image lasts a shorter time, but is longer with administration to caffeine (cites Zislina 1955). Thus the visual cortex not only synthesizes elements but also stabilizes them, similar to the temporal lobe after injury with respect to auditory elements.

Associative visual blindness (associative visual agnosia) as opposed to apperceptive agnosia is intact perception, abnormal recognition.