The brain requires many functions to span the gap from visual sensation to perception. Our studies indicate that different visual areas in the brainmay communicate via temporally modulated messages, suggesting that understanding these temporally encoded messages may give clues to the types of functional processes involved in visual information processing. New evidence suggests one such functional role for neurons in inferior temporal (IT) cortex during a short-term visual memory task. In all visual areas studied to date, neurons encode information about pictures in a multidimensional temporal code. We are now recording from individual neurons during a short-term visual memory task. Neurons in the IT cortex appear to send three messages during a pattern recognition task. One message describes the current picture, another describes the previous picture, and a third indicates which behavioral response is required. These results lead to a new hypothesis concerning the role of IT neurons in short-term visual memory tasks: the memory-wave hypothesis, which states that neurons in the inferior temporal cortex receive input from separate visual and memory systems. These inputs consist of temporally modulated waves of activity. The temporal waveform of the response of IT neurons is formed by multiplying these two input waveforms together. This product may represent the first part of a temporal correlation process used to determine whether the temporal messages in the visual pathway match the temporal messages recalled from the memory system. The most exciting prediction of this hypothesis is that the purpose of the short-term memory system is to generate a replica of the waveform originally elicited by the visual stimulus.
