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Abstract:
The contribution of temporal cortex (TE) to vision has been studied extensively in both human and nonhuman primates. Experiments in both species have focused on the consistency of neuronal responses to stimuli presented in a particular context in defining a functional role for TE in vision, however, the role of TE in cognition remains unknown. Do cells in TE respond differently to the same visual stimulus depending on the context in which it must be evaluated, or does their response remain the same, faithfully representing the sensory input? In order to address this question, we taught two monkeys (macaca mulatta) to perform a classification (CL) / identification (ID) task. Each trial began with the presentation of a colored frame, indicating the task the animal was to perform (blue - CL, orange - ID), followed by the presentation of a stimulus from one of a number of object classes (spheroids, wires, faces, monkeys, cars, greebles). The animal indicated its response by pressing one of 18 buttons. In the CL task, the animals were taught to group similar stimuli together by pressing one of 9 buttons located in front of their left hand for every member belonging to a class (e.g., button 1 for all faces), while, in the ID task, the animals had to use their right hand to indicate which of nine individuals from a given class had been presented. The learning of new classes of stimuli, as well as new individuals, was accompanied by an increase in reaction time and error rate that improved with training until performance for the two tasks was not significantly different. In currently ongoing, combined psychophysical-physiological experiments, the responses of single neurons in both medial and lateral aspects of TE are being evaluated with respect to task context.
