Cerebellar degeneration selectively disrupts continuous mental operations

ABSTRACT

Inspired by computational models of how the cerebellum supports the coordination of movement, we propose a novel hypothesis to specify constraints on how this subcortical structure contributes to higher-level cognition. Specifically, we propose that the cerebellum helps facilitate dynamic continuous transformations of mental representations (CoRT). To test this hypothesis, we compared the performance of individuals with cerebellar degeneration (CD) on tasks that entail continuous movement-like mental operations with tasks that entail more discrete mental operations. In the first pair of experiments, individuals with CD were impaired on a mental rotation task, showing a slower rate of mental rotation compared to control participants. In contrast, the rate at which they scanned discrete representations in visual working memory was similar to that observed in the control group. In the second pair of experiments, we turned to mathematical cognition as a test of the generality of the CoRT hypothesis. Individuals with CD were selectively impaired in adding single-digit numbers, a task hypothesized to entail a mental operation involving continuous transformations along a mental number line. In contrast, their rate of performing arithmetic operations thought to involve retrieval from a look-up table was unimpaired. These results, obtained in disparate task domains, suggest a general role for the cerebellum in coordinating dynamic transformations in mental space, paralleling key features of computational theories concerning the cerebellum’s role in coordinated movement.