NEURAL SYSTEMS UNDERLYING LEARNING AND REPRESENTATION OF GLOBAL MOTION

We demonstrate performance-related changes in cortical and cerebellar activity, The largest learning-dependent changes were observed in the anterior lateral cerebellum, where the extent and intensity of activat ion correlated inversely with psychophysical performance. After learni ng had occurred (a few minutes), the cerebellar activation almost disa ppeared; however, it was restored when the subjects were presented wit h a novel, untrained direction of motion for which psychophysical perf ormance also reverted to chance level. Similar reductions in the exten t and intensity of brain activations in relation to learning occurred in the superior colliculus, anterior cingulate, and parts of the extra striate cortex. The motion direction-sensitive middle temporal visual complex was a notable exception, where there was an expansion of the c ortical territory activated by the trained stimulus. Together, these r esults indicate that the learning and representation of visual motion discrimination are mediated by different, but probably interacting, ne uronal subsystems.