The structure and function of the human visual pathway

The authors present the fundamen­tals and some recent data on the human visal pathway obtained by the new imaging tech­niques of the cerebral cortex and non-inva­sive electrophysiological and other methods. Perception of colours and motion is explained in the light of the new findings of parallel par- vocellular (P) and magnocellular (M) pathways. Discrimination of colours is rendered possible by the following important structures of the P pathway: P ganglion cells in the retina – parvo- cellular layers in the thalamic lateral geniculate nucleus (LGN) – »blob« regions in the primary visual cortex V1 – V4 visual area. Important structures of the M pathway providing for the dis­crimination of motion include: M ganglion cells in the retina – magnocelllular layers in the LGN – primary visual cortex V1 – V5 visual area. Location of other cortical areas involved in vision is presented; the visual pathway responsible for what is seen ends in the temporal cortex, and the pathway concerned with motion (where the objects are) ends in the parietal cortex. Clinical data for cerebral achromatopsia (complete colour blindness), akinetopsia (inability to discern move­ment of objects), prosopagnosia (inability to recognise familiar faces), also speak for the existence of several functionally specialised visu­al cortical areas. For the conscious perception of light and movement