Climbing fiber inputs to the cerebellum encode error signals that instruct learning. Recently, 26evidence has accumulated to suggest that the cerebellum is also involved in the processing 27 of reward. To study how rewarding events are encoded, we recorded the activity of climbing 28 fibers when monkeys were engaged in an eye movement task. At the beginning of each trial, 29 the monkeys were cued to the size of the reward that would be delivered upon successful 30 completion of the trial. Climbing fiber activity increased when the monkeys were presented 31 with a cue indicating a large reward size. Reward size did not modulate activity at reward 32 delivery or during eye movements. Comparison between climbing fiber and simple spike 33 activity indicated different interactions for coding of movement and reward. These results 34indicate that climbing fibers encode the expected reward size and suggest a general role of 35 the cerebellum in associative learning beyond error correction. 36

Climbing fiber inputs to the cerebellum encode error signals that instruct learning. Recently, evidence has accumulated to suggest that the cerebellum is also involved in the processing of reward. To study how rewarding events are encoded, we recorded the activity of climbing fibers when monkeys were engaged in an eye movement task. At the beginning of each trial, the monkeys were cued to the size of the reward that would be delivered upon successful completion of the trial. Climbing fiber activity increased when the monkeys were presented with a cue indicating a large reward, but not a small reward. Reward size did not modulate activity at reward delivery or during eye movements. Comparison between climbing fiber and simple spike activity indicated different interactions for coding of movement and reward. These results indicate that climbing fibers encode the expected reward size and suggest a general role of the cerebellum in associative learning beyond error correction.

The basal ganglia and the cerebellum are major subcortical structures in the motor system. The basal ganglia have been cast as the reward center of the motor system, whereas the cerebellum has been hypothesized to be involved in adjusting sensorimotor parameters. Recent findings of reward signals in the cerebellum have challenged this dichotomous view. To directly compare the basal ganglia and the cerebellum we recorded from oculomotor regions in both structures from the same monkeys. We partitioned the trial-by-trial variability of the neurons into reward and eye-movement signals to compare the coding within and across structures. Reward expectation and movement signals were the most pronounced in the output structure of the basal ganglia, intermediate in the cerebellum, and the smallest in the input structure of the basal ganglia. These results indicate different information convergence properties within these structures and demonstrate differences in internal computations.

The Substantia Nigra pars reticulata (SNpr), an output structure of the basal ganglia, has been hypothesized to gate the execution of movements. Previous studies focusing mostly on saccadic eye movements have reported that SNpr neurons are tonically active and either pause or increase their firing during movements, consistent with the gating role. We recorded activity in the SNpr of two monkeys during smooth pursuit and saccadic eye movements. SNpr neurons exhibited highly diverse reaction patterns during pursuit, including frequent increases and decreases in firing rate, uncorrelated responses in different movement directions and in reward conditions resulting in the high dimensional activity of single neurons. These diverse temporal patterns surpassed those in other oculomotor areas in the frontal cortex, basal ganglia, and cerebellum. These results suggest that temporal properties of the responses enrich the coding capacity of the basal ganglia output beyond gating or permitting movement.

The basal ganglia and the cerebellum are major subcortical structures in the motor system. The basal ganglia have been cast as the reward center of the motor system, whereas the cerebellum has been hypothesized to be involved in adjusting sensorimotor parameters. Recent findings of reward signals in the cerebellum have challenged this dichotomous view. To directly compare the basal ganglia and the cerebellum we recorded from oculomotor regions in both structures from the same monkeys. We partitioned the trial-by-trial variability of the neurons into reward and eye-movement signals to compare the coding within and across structures. Reward expectation and movement signals were the most pronounced in the output structure of the basal ganglia, intermediate in the cerebellum, and the smallest in the input structure of the basal ganglia. These results indicate different information convergence properties within these structures and demonstrate differences in internal computations.