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Abstract:
In order to investigate the possibility of a more cognitive role for inferior temporal (IT) cortex in visual recognition, we trained two monkeys (macaca mulatta) to perform a classification (CL) / identification (ID) task in which the animal had to classify or identify a particular stimulus depending on a cue presented at the beginning of the trial. Here we compare the responses of neurons in ventral STS and lateral and ventral TE to identical stimuli presented in the context of two different recognition tasks.
Of the 399 neurons recorded to date, roughly 20 were visually responsive to the stimuli presented in the task (86 excitatory, 14 inhibitory). While the majority of neurons (70) exhibited task-context independent responses, a small population (30, 23/78) did respond significantly differently to one or more, but never to all, stimuli depending on the task. Closer examination of this population of task-context dependent neurons revealed that the vast majority (21/23) fired more for the stimulus or stimuli for which they showed a significant difference in the context of the CL task. Moreover, only 3 of these cells responded selectively (more than 2:1 over the next best stimulus) to any of the stimuli presented, although 15/78 were selective in one or both tasks by the same criterion.
These results indicate that IT neurons may be contributing more than just a faithful representation of the sensory input in the act of visual recognition. Additionally, task-context dependent information does not appear to be correlated with the selectivity for complex stimuli often observed in the responses of IT neurons.
