Saturday, March 17, 2007

Categorization Training Results in Shapeand Category-Selective Human Neural Plasticity

Xiong Jiang, Evan Bradley, Regina A. Rini, Thomas Zeffiro, John VanMeter, Maximilian Riesenhuber
Neuron 53, 891–903, March 15, 2007

Object category learning is a fundamental ability, requiring the combination of ‘‘bottom-up’’ stimulus-driven with ‘‘top-down’’ task-specific information. It thereforemay 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 ategorization, 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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