THE CONTRIBUTION OF THE CEREBELLUM TO COGNITION: AN fMRI STUDY IN VERBAL WORKING MEMORY

Open Access
Author:
Medaglia, John Dominic
Graduate Program:
Psychology
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
March 28, 2011
Committee Members:
  • Frank Gerard Hillary, Thesis Advisor
  • Rick Owen Gilmore, Thesis Advisor
  • Peter Andrew Arnett, Thesis Advisor
Keywords:
  • functional connectivity
  • fMRI
  • cerebellum
  • working memory
Abstract:
Two decades of research support the notion that the cerebellum contributes to cognitive processes such as executive functions and working memory in addition to motor functions. A number of distinct literatures now provide a framework for investigating the hypothesis that the cerebellum contributes to cognition and specifically working memory. First reviewed is evidence from paleontological, comparative and psychological studies demonstrating that the earliest cerebellum-like structures evolved in conjunction with complex senses and presently maintain a role in a wide range of sensory and other nonmotor processes across species. Neuroanatomical studies have revealed several that cortico-cerebellar structural loops integrate an extended network between the frontal and parietal cortices and the cerebellum and findings in modern human development reveal a tight functional relationship between the cerebellum and dorsolateral prefrontal cortex. Studies of executive functions and working memory in neuropsychology and neuroimaging found broad ranging involvement of the cerebellum in many higher order tasks, with pronounced involvement in verbal working memory. These literatures show that the cerebellum has a complex and nuanced functional relationship to the neocortex, but its role in working memory remains poorly explained. For example, the cerebellum’s influence on task performance has not been examined in the context of a distributed functional network during a continuous working memory task. It is a goal of the current thesis to review specific evidence supplied by multiple domains of inquiry that provide a framework for understanding the cerebellum’s role in modern human cognition, especially in executive functions and verbal working memory. Based upon this review, the current study investigated the contribution of the cerebellum to performance in verbal working memory and the relationships between activity in the cerebellum to several cortical regions in the context of a continuous verbal working memory task, the n-back, using functional magnetic resonance imaging and functional connectivity analyses. Reaction time was found to decrease during performance of both verbal working memory tasks. In general, the BOLD signal in the cerebellum was highly related to that in the contralateral prefrontal and parietal cortices. Unified structural equation modeling revealed that cerebellar influences on motor and cognitive regions were equivalent with the exception of the early and late portions of the 2-back task, during which the left cerebellum demonstrated high connectivity with the right prefrontal and parietal cortices. These findings suggest that the cerebellum is highly interactive with cognitive regions during verbal working memory, including regions thought to be involved in cognitive control.