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Abstract:
Identical sensory information often needs to be interpreted and responded to in different ways. For example, identification may require the viewer to pay attention to different information in a visual stimulus than classification. Is task-context-specific processing of a visual stimulus represented in the responses of IT neurons?
We trained two monkeys (macaca mulatta) to perform a classification / identification task in which the animal had to classify or identify a particular stimulus depending on a cue presented at the beginning of the trial.
We analyzed the activity of 356 visually responsive neurons. While the majority of these neurons (65) responded nearly the same to a stimulus regardless of the task, a considerable population (35, 126/356) exhibited task-context dependent responses, firing significantly differently to one or more, but never to all, stimuli depending on the task. As a population, task-context dependent neurons fired significantly more during the classification task. A contrast-based selectivity index revealed that these neurons did not respond more selectively to stimuli in the context of the identification task.
In conclusion, IT neurons are more active during classification. Moreover, task-context dependent responses do not appear to be correlated with visual selectivity. A possible explanation for this, perhaps unexpected, effect is that less specificity and broader tuning results in the activation of larger populations which may lead to an increase in the response of individual units during classification. One model of recognition does indeed predict this outcome.
