The goal of this research is to elucidate the role of the cerebellum in cognitive function by combining sophisticated event-related functional magnetic resonance imaging (fMRI) and transcranial magnetic stimulation (TMS) techniques with tasks of human verbal working memory. Using the Sternberg paradigm as the test of verbal working memory, we hypothesize that regions of the cerebellum can be differentially activated by sensory acquisition, motor control-error correction, and executive search processes. We further hypothesize that by increasing cognitive demands separately during these encoding, maintenance and retrieval phases, corresponding process-specific increases in the same regional cerebellar activation will occur. We will further test for which of the fMRI-identified regions of activation are necessary for performance using TMS, a technique for producing a transient functional disruption of neural circuitry. We will develop methods and software for integration fMRI and TMS, use TMS to disrupt cerebellar, neocortical and both cerebellar and neocortical areas known to activate during working memory, and cerebellar regions shown to activate during verbal working memory as a determined by our fMRI studies. These data will lead to two studies of cerebro-cerebellar interactions in cognition, in which we hypothesize that: (1) frontal-cerebellar and temporal/parietal-cerebellar circuits are linked with the articulatory control and phonological store components of working memory, and (2) search and selection are dissociable in explicit, semantic, and working memory retrieval. Upon completion of this project, the processes that influence cerebella activation for higher cognitive function, the importance of these activations for task performance, and the specific interactions of cortical and cerebellar function for cognitive performance will be defined with greater psychological specification and localization than ever before.
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