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Publications and source records attributed to Ipata, A. E..
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Although the cerebellum has been traditionally considered to be exclusively involved in motor control, recent anatomical and clinical studies show that it also has a role in reward-processing. However, the way in which the movement related and the reward related neural activity interact at the level of the cerebellar cortex and contribute towards learning is still unclear. Here, we studied the simple spike activity of Purkinje cells in the mid-lateral cerebellum when monkeys learned to associate a right or left-hand movement with one of two visual symbolic cues. These cells had distinctly different discharge patterns between an overtrained symbol-hand association and a novel symbol-hand association, responding in association with the movement of both hands, although the kinematics of the movement did not change between the two conditions. The activity change was not related to the pattern of the visual symbols, the movement kinematics, the monkeys reaction times or the novelty of the visual symbols. The simple spike activity changed with throughout the learning process, but the concurrent complex spikes did not instruct that change. Although these neurons also have reward-related activity, the reward-related and movement-related signals were independent. We suggest that this mixed-selectivity may facilitate the flexible learning of difficult reinforcement learning problems.
Climbing fiber input to Purkinje cells has been thought to instruct learning related changes in simple spikes and cause behavioral changes through an error-based learning mechanism. Although, this framework explains simple motor learning, it cannot be extended to learning higher-order skills. Recently the cerebellum has been implicated in a variety of cognitive tasks and reward-based learning. Here we show that when a monkey learns a new visuomotor association, complex spikes predict the time of the beginning of the trial in a learning independent manner as well as encode a learning contingent reward expectation signal after the stimulus onset and reward delivery. These complex spike signals are unrelated to and were unlikely to instruct the reward based signal found in the simple spikes. Our results provide a more general role of complex spikes in learning and higher-order processing while gathering evidence for their participation in reward based learning.
How do we learn to establish associations between arbitrary visual cues (like a red light) and movements (like braking the car)? We investigated the neural correlates of visuomotor association learning in the monkey mid-lateral cerebellum. Here we show that, during learning but not when the associations were overlearned, individual Purkinje cells reported the outcome of the monkeys most recent decision, an error signal, which was independent of changes in hand movement or reaction time. At the population level, Purkinje cells collectively maintained a memory of the most recent decision throughout the entire trial period, updating it after every decision. This error signal decreased as the performance improved. Our results suggest a role of mid-lateral cerebellum in visuomotor associative learning and provide evidence that cerebellum could be a generalized learning system, essential in non-motor learning as well as motor learning.
Although the cerebellum has been traditionally considered to be exclusively involved in motor control and learning, recent anatomical and clinical studies suggest that it may also have a role in cognition. However, no electrophysiological evidence exists to support this claim. Here we studied the activity of simple spikes of hand-movement related Purkinje cells in the mid-lateral cerebellum when monkeys learned to associate a well-learned right or left-hand movement with one of two visual symbolic cues. The cells had distinctly different discharge patterns between an overtrained symbol-hand association and a novel symbol-hand association although the kinematics of the movement did not change between the two conditions. The activity change was not related to the pattern of the visual symbols, the hand making the movement, the monkeys reaction times or the novelty of the visual symbols. We suggest that mid-lateral cerebellum is involved in higher-order cognitive processing related to learning a new visuomotor association.\n\nOne Sentence SummaryHand-movement related Purkinje neurons in midlateral cerebellum, which discharge during an overtrained visuomotor association task, change their activity when the monkey has to associate the same movements with new cues, even though the kinematics of the movements do not change.