A NEURAL SYSTEM FOR HUMAN VISUAL WORKING-MEMORY

Working memory is the process of actively maintaining a representation of information for a brief period of time so that it is available for use, In monkeys, visual working memory involves the concerted activit y of a distributed neural system, including posterior areas in visual cortex and anterior areas in prefrontal cortex, Within visual cortex, ventral stream areas are selectively involved in object vision, wherea s dorsal stream areas are selectively involved in spatial vision, This domain specificity appears to extend forward into prefrontal cortex, with ventrolateral areas involved mainly in working memory for objects and dorsolateral areas involved mainly in working memory for spatial locations, The organization of this distributed neural system for work ing memory in monkeys appears to be conserved in humans, though some d ifferences between the two species exist, In humans, as compared with monkeys, areas specialized for object vision in the ventral stream hav e a more inferior location in temporal cortex, whereas areas specializ ed for spatial vision in the dorsal stream have a more superior locati on in parietal cortex, Displacement of both sets of visual areas away from the posterior perisylvian cortex may be related to the emergence of language over the course of brain evolution, Whereas areas speciali zed for object working memory in humans and monkeys are similarly loca ted in ventrolateral prefrontal cortex, those specialized for spatial working memory occupy a more superior and posterior location within do rsal prefrontal cortex in humans than in monkeys, As in posterior cort ex, this displacement in frontal cortex also may be related to the eme rgence of new areas to serve distinctively human cognitive abilities.