[Visual information processing from the retina to the prefrontal cortex]

Studies on the neural bases of visual information processing were reviewed by tracing connections from the retina to the prefrontal cortex in the monkey; i.e., retina--lateral geniculate body (LGB)--striate cortex--prestriate cortex--inferotemporal (IT) cortex or posterior parietal (PP) cortex--prefrontal cortex. The retinotopy exists up to the level of prestriate cortex, but it is lost in the IT or PP cortex. A general tendency is observed that the later is the stage of information processing, the longer is the latency of cell activity changes, the larger is the size of receptive field, and more complex become trigger features. Small spot stimuli activate retinal ganglion cells or LGB cells while bars or edges with proper orientation are trigger stimuli for striate and some prestriate cells. In restricted prestriate areas, cells which are selective to color or movement are observed. IT cells are activated by complex pattern stimuli, while PP cells are selective to spatial aspects of the stimulus. Some prefrontal cells encode the meaning of the stimulus independent of its physical properties.