The Neural Control of Vision
N. Intermediate Level Vision

Yet another task that examines intermediate visual capacities that have to do with the selection of targets that are less salient is shown in Figure 76. In this case the oddity task was used as previously described. The discrimination has to be made on the basis of brightness differences. On the left the target is always brighter than the comparison stimuli whereas on the left the target is dimmer than the comparison stimuli. V4 lesions produce a major deficit in the monkey's ability to select the "lesser" target. Another parameter we studied was the relative size of the stimuli; similar major deficit was obtained when the monkey was asked to selected a target that was smaller than the comparison stimuli. Not only is there a deficit in performance, but it takes the monkey significantly longer to carry out the task after the V4 lesion.