Neuronal Representation of Pictorial Working Memory in the Primate Temporal Cortex

Abstract

It has been proposed that visual memory traces are located in the temporal lobes of the cerebral cortex, as electric stimulation of this area in humans results in recall of imagery¹. Lesions in this area also affect recognition of an object after a delay in both humans^2,3 and monkeys^4–7, indicating a role in working memory of images⁸. Single-unit recordings from the temporal cortex have shown that some neurons continue to fire when one of two or four colors are to be remembered temporarily⁹. However, neuronal responses selective to specific complex objects^10–18, including hands^10,13 and faces^13,16,17 cease soon after the offset of stimulus presentation^10–18. These results left it open whether any of these neurons could serve memory of the object. We have recently found a group of shape-selective neurons in an anterior ventral part of the temporal cortex of monkeys that exhibited sustained activity during the delay period of a visual working memory task^19,20. The activity was highly selective for the pictorial information to be memorized and was independent of the physical attributes such as size, orientation, color or position of the object. These observations indicate that the delay activity represents the working memory of categorized percept of a picture. This article discusses the implications of these findings in the cognitive neuroscience.