Cognition and Action In The Cortico-Cerebellar System

Skill learning is the process of acquiring the ability to execute a task not only more efficiently, but also more automatically so that it is not prone to disruption from other tasks being conducted at the same time. The ability to acquire skills must depend in some way on physical changes that take place during learning within the circuits of the brain, but little is understood about these processes. Previous work has suggested that during the learning of skilled movements these changes may take place within the circuits of the cerebellum. The integrity of the cerebellum is important for the learning of skilled movements because this ability is severely impaired in patients who have suffered damage to cerebellar circuits. Brain imaging methods enable researchers to find activity in the brain that is related to particular tasks executed during scanning (giving a 'snapshot' of activity related to specific tasks). These methods have been used to demonstrate that during the execution of skilled movement, activity of specific cerebellar areas is increased in healthy human volunteers. The cerebellum operates as part of a well-known circuit that it forms with areas of the cerebral cortex (the cortico-cerebellar system), and it has been suggested that an important neural process that underlies our ability to acquire skilled movements includes a transition from cortical control to cerebellar control. The purpose of this project is to use brain imaging methods to test the idea that the cortico-cerebellar system is engaged not only during the learning of skilled actions, but also during the development of mental skills (arithmetic skills in particular). In particular, it will test the idea that during motor skill learning activity in the motor cortex declines, but activity in interconnected cerebellar areas increases as these areas gradually 'take over' the role of the cortical areas. It will also test the idea that as mental skills become more efficient and increasingly immune to the disrupting influences of external events during scanning, activity in the prefrontal cortex (the cortical area most heavily implicated in higher functions) will decrease, while interconnected parts of the cerebellar cortex will increase. The detection and correction of errors is important for the process of learning. Experiments will therefore also test the idea that these cerebellar areas are sensitive to systematically introduced errors in the control of skilled movement and mental information processing. Newly developed methods have made it possible to use functional neuroimaging to study the ways in which brain areas communicate to achieve particular information processing goals. Studies in this project will examine the ways in which the communication between cortical and cerebellar areas gradually changes as normal healthy volunteers learn mental and motor skills in the scanner. Collectively, these experiments will provide a better understanding of how information processing in the human brain changes during the course of skill learning.

The overarching goal of the proposed research is to use functional magnetic resonance imaging (fMRI) to investigate the temporal dynamics of activity in the human brain during the acquisition of motor and cognitive skills. Although previous work has shown learning-related activity changes in prefrontal cortex, motor cortex and cerebellum during motor learning, there is no coherent explanation of their involvement in motor skill learning that is consistent with the recently characterised anatomy of the primate cortico-cerebellar system. Recent evidence suggests that this system may also be involved in the acquisition of cognitive skills. I propose the specific involvement of two separate cortico-cerebellar networks in the acquisition of motor and cognitive skills. Experiments will test the long-standing idea that skill learning involves the transition of control from cortical areas during the early phases of learning, to cerebellar circuits in the later phases when the execution of skilled information processing becomes automatic and is less susceptible to additional demands. Specifically, I propose that during the acquisition of motor skills, the cortical motor areas that are initially engaged relinquish control to interconnected cerebellar areas (lobules HV and HVI). I also suggest that during the acquisition of cognitive skills, a similar transition occurs from prefrontal area 46 to its interconnected counterpart in the cerebellar cortex. Studies will additionally examine the responses of these areas to systematically introduced errors, and will also examine the temporal dynamics of information flow between cortical and cerebellar areas in each form of learning. Collectively, these experiments will give new insights into the way that anatomically well-defined cortico-cerebellar circuits become engaged in the acquisition of motor and cognitive skills in the human brain.