Can we improve slow learning in cerebellar patients?

We tested whether training paradigms targeting slow learning alleviate motor learning deficits of cerebellar patients compared to matched controls using four visuomotor tasks: standard, gradual, overlearning and long intertrial interval. We measured slow learning using spontaneous recovery, the return to learned adaptation after brief wash out of fast adaptation. Spontaneous recovery increased in both groups only in overlearning. A model of adaptation suggested that in controls the increase reflects changes in slow system dynamics. In contrast, because cerebellar participants plateaued more slowly than controls, added trials in models of cerebellar participants increased the level of slow learning. Whereas, under the model, slow learning became more resilient in controls, there was no change in its dynamics for cerebellar participants. Our results and modeling suggest that while residual slow learning does exist in cerebellar patients and can be expressed through increased training trials, the primary cerebellar deficit cannot be improved by overlearning paradigms.