Visual cognition and its disorders


Authors: F. Koukolík
Authors‘ workplace: Oddělení patologie a molekulární medicíny ;  Národní referenční laboratoř prionových chorob ;  Fakultní Thomayerova nemocnice s poliklinikou, Praha ;  Primář: MUDr. František Koukolík, DrSc.
Published in: Prakt. Lék. 2008; 88(3): 140-145
Category: Various Specialization

Overview

The visual system of the brain is functionally specialized. The visual information is processed through two main streams, dorsal and ventral, called the WHERE system and the WHAT system. V1, V2 and V3 are visual cortical maps at the posterior and medial hemispheral surface. Human V4 (hV4) and VO1 (ventral occipital 1) are visual cortical maps at the ventral surface of the occipital lobe. Dorsal visual cortical maps V3A, V3B and V7 are situated forwardly from the posterior part of intraparietal sulcus. Lateral visual cortical maps hMT1 and LOC (lateral occipital complex) are situated from the occipital pole to the superior temporal sulcus. The brain system of colour cognition starts with S, M and L retinal cones. Its hierarchical focal point is called V4. Cerebral achromatopsia is a result of damage to V4. Neurons of the hMT V5 visual cortical area are tuned to motion recognition. Akinetopsia results from damage to this cortical area. There are three cortical areas activated in visual object cognition. Their damage results in visual object agnosia. Face cognition is socially fundamental in humans and other social primates. Its hierarchical focal point is the fusiform face area, FFA. Damage here results in prosopagnosia. Four types of topographical disorientation are due to damage of ego- and/or exocentric representational systems.

Key words:
system WHERE, system WHAT, visual cortical maps, achromatopsia, akinetopsia, visual object agnosia, prosopagnosia, topographical disorientation.


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