Abstract
It is generally understood that the main role of the cerebellum is in movement planning and coordination, but neuroimaging has led to striking findings of its involvement in cognitive processing. Visualization is a key cognitive process in a wide range of ‘internal’ and ‘externalized’ functionalities, from learning and memory to artistic creativity and engineering design. Here we use fMRI and the SUIT toolbox to investigate the involvement of the cerebellum in mental visualization, and Granger Causal connectivity to analyze its progressive interplay with the whole-brain visualization network. For each of a set of complex spatial structures in the form of line-drawings, sighted adults performed in a 3T scanner i) visual exploration (30s) and ii) visualization-from-memory of the explored images (30s), interleaved with fixation periods (20s); each scan consisted of three repeats of this sequence. A well-structured visualization network of activated and suppressed regions was identified in the cerebellum. The change in activation with the visualization and perceptual exploration repeats in each region-of-interest (ROI) was analyzed to define the temporal evolution of the rapid learning process. In visualization, positive caudal cerebellar ROIs showed significant increases in the level of activation as the learning progressed across repeats, while negative Crus I/II ROIs showed significantly increased negative signal, implying a progressive differentiation of the cerebellar responses; comparative analysis of the exploration revealed an interplay of overlapping and contrasting learning effects. The causal connectivity analysis uncovered a characteristic dynamics of cross-coupling between key cerebellar ROIs and large-scale brain networks, such as the default mode network (DMN). These multidimensional fMRI and connectivity findings laid a solid basis for a novel framework of rapid cerebro-cerebellar reorganization. They provide important insights into fundamental questions of cognitive cerebellar function, and also have implications for the development of practical methods for enhancing the cognitive abilities of learning and memory.