Neuronal Responses to Object Images in the Macaque Inferotemporal Cortex at Different Stimulus Discrimination Levels

Abstract

We can discriminate visual objects at multiple levels, from coarse categorization to individual identification. It is not known how the brain adapts to the varying levels of discrimination required in different behavioral contexts. In the present study, we investigated whether the stimulus selectivity of neuronal responses in the monkey inferotemporal cortex, which is the final unimodal stage in the ventral visual pathway, changes with the varying levels of discrimination required for different task conditions. Responses of each inferotemporal cell to the same set of nine object images were examined in two different task conditions. The task alternated between coarse and fine discriminations in the first experiment, and the rule alternated between categorization and individual object identification in the second experiment. Despite these changes in the task requirements and the resulting differences in the monkeys' behavior, we found that the responses of inferotemporal cells were largely unchanged in both experiments. Our results suggest that representation of object images in the inferotemporal cortex is stable and rather insensitive to these kinds of shifts in behavioral context. Neuronal adaptations to behavioral context may occur downstream of the inferotemporal cortex.