Selective recruitment of cerebellum in cognition
Abstract
Previous studies of cerebellar function in humans have shown that it is activated by a myriad of tasks ranging from motor learning and language to working memory and more. These studies have prompted a deviation from the traditional view of the cerebellum as a purely motor structure. However, the precise contribution of the cerebellum to these tasks remains ambiguous.
A prevalent assumption in fMRI studies is interpreting BOLD activation as evidence of the cerebellum's involvement in specific tasks. However, this interpretation is potentially misleading, especially considering that the BOLD signal predominantly represents cerebellar input, with output activity largely absent. Consequently, observed activations in the cerebellum may merely reflect the transmission of signals via fixed anatomical connections with the neocortex, independent of any requisite cerebellar computations.
To circumvent this interpretative limitation, we present a novel framework. First, we take advantage of the diversity of tasks in a multi-domain task battery, proposing a \textbf{task-invariant model of cortico-cerebellar connectivity}. This model predicts cerebellar activation levels based on neocortical inputs. Building on this, we introduce the concept of \textbf{"selective recruitment"} to examine cerebellar-specific processes via functional MRI. Drawing insights from cerebellar patient studies, we validate this framework in the motor domain, demonstrating that the cerebellum's input is gated based on task requirements, with intensified activation at higher speeds.
Venturing into a more complex domain, we test the framework in a working memory task; A task with subtler deficits and inconclusive cerebellar patient study outcomes. We reveal that the cerebellum becomes selectively engaged during the encoding of substantial information loads, as demonstrated with six items in our task.
In sum, our approach of investigating selective cerebellar recruitment, particularly in areas where patient studies offer limited clarity, paves the way for a more holistic comprehension of the cerebellum's nuanced roles, enriching our appreciation of this intricate "little brain."