2017 doi: 10.1152/jn.00209.2017. P-cells PKI-402 favored error. From these results, we inferred the anatomy of a sensory-to-motor adaptive controller that transformed visual error vectors into motor-corrections. Introduction Cerebellar Purkinje cells, P-cells, produce high frequency simple spikes to predict kinematics of the ongoing movement1C6. These simple spikes are flexible, changing following experience of a sensory error7C9, which are transmitted to P-cells from your inferior olive10, resulting in complex spikes (CS)11C13. However, CSs are rare events that occur approximately once per second14, producing a disparity between richness of information regarding predictions via the simple spikes, and the poverty of sensory error information in the CSs. Indeed, errors can double15,16 or halve in size17 without significant changes in CS rates. How can P-cells accurately produce simple spikes when their teacher is seemingly so impoverished in its encoding of sensory errors? One possibility is usually that error magnitude modulates the shape of CS waveforms. Properties of a sensory stimulus can affect the number of spikes in the climbing fiber18, thereby altering the duration of the producing CS waveform19,20. A longer CS waveform has been shown to induce a larger change in the simple spikes, producing a larger switch in behavior21,22. Another possibility is usually that error magnitude may impact CS PKI-402 timing. The latency of the CS with respect to simple spikes in the flocculus has been shown to modulate plasticity at the parallel fiber to P-cell synapse23. That is, CSs that arrive MMP19 during a precise temporal windows may have a larger effect on the simple spikes by maximizing the switch in the strength of the recently active P-cell synapses. Here, we considered saccadic eye movements to visual targets. At saccade end, sometimes the eyes missed the target, resulting in an error. We quantified how CSs encoded the vector space of visual errors, how this encoding changed the simple spikes that were produced in the subsequent saccade, and how the motor output in this subsequent saccade differed from those that the animal experienced produced before the experience of error. We found that in the oculomotor vermis, each P-cell experienced a preference for a specific direction of visual error16,24, with the error direction encoded in the probability of generating a CS. However, the magnitude of that error vector affected the CS timing. As the error became larger, CS timing became less variable and more likely to occur during a specific temporal windows: the windows that was most effective in inducing plasticity. Intriguingly, CSs that occurred in this temporal windows were of longer period. Using trial-by-trial analysis7,9,21, we observed a chain of events that tied the P-cells favored direction of error in visual-space to a vector of pressure production in motor-space. From these functional results we made an anatomical inference. The error preference in a region of sensory-space, as signaled by the CSs, organized the P-cells into a computational unit that collectively predicted movement kinematics4. That preference for error also organized the downstream projections of the computational unit so that, through learning, the P-cells altered the motor output only along a vector that was parallel to their favored error. Results We analyzed simple and PKI-402 CSs of n=67 well-isolated P-cells from your oculomotor vermis of 7 monkeys in 187,008 trials. Each trial began with fixation on a visual target. After a random interval the target was relocated to a new location 10C25 away, resulting in a saccadic eye movement16,24,25..
