Abstract
Object category learning is a fundamental ability, requiring the combination
of "bottom-up" stimulus-driven with "top-down" task-specific information.
It therefore may be a fruitful domain for study of the general neural
mechanisms underlying cortical plasticity. A simple model predicts
that category learning involves the formation of a task-independent
shape-selective representation that provides input to circuits learning
the categorization task, with the computationally appealing prediction
of facilitated learning of additional, novel tasks over the same
stimuli. Using fMRI rapid-adaptation techniques, we find that categorization
training (on morphed "cars") induced a significant release from adaptation
for small shape changes in lateral occipital cortex irrespective
of category membership, compatible with the sharpening of a representation
coding for physical appearance. In contrast, an area in lateral prefrontal
cortex, selectively activated during categorization, showed sensitivity
posttraining to explicit changes in category membership. Further
supporting the model, categorization training also improved discrimination
performance on the trained stimuli.
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