HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) All Versions of this Article: 100/5/2825    most recent 90221.2008v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Web of Science (3) Citing Articles via Google Scholar Google Scholar Articles by Bo, J. Articles by Bastian, A. J. Search for Related Content PubMed PubMed Citation Articles by Bo, J. Articles by Bastian, A. J.

A Cerebellar Deficit in Sensorimotor Prediction Explains Movement Timing Variability

¹Kennedy Krieger Institute; ²Departments of Neurology, Neuroscience, and Physical Medicine and Rehabilitation, The Johns Hopkins University School of Medicine, Baltimore; and ³Department of Kinesiology, University of Maryland, College Park, Maryland

Submitted 4 February 2008; accepted in final form 16 September 2008

A popular theory is that the cerebellum functions as a timer for clocking motor events (e.g., initiation, termination). Consistent with this idea, cerebellar patients have been reported to show greater deficits during hand movements that repeatedly start and stop (i.e., discontinuous movements) compared with continuous hand movements. Yet, this finding could potentially be explained by an alternate theory in which the cerebellum acts as an internal model of limb mechanics. We tested whether a timing or internal model hypothesis best explains results from a circle-drawing task, where individuals trace a circle with the hand at a desired tempo. We first attempted to replicate prior results showing greater impairment for discontinuous versus continuous circling movements, and then asked whether we could improve patient performance by reducing demands in each domain. First, we slowed the movement down to reduce the need to predict and compensate for limb dynamics. Second, we supplied external timing information to reduce the need for an internal event timer. Results showed that we did not replicate the previous findings—cerebellar patients were impaired in both discontinuous and continuous movements. Slowing the movement improved cerebellar performance to near control values. The addition of an external visual timing signal paradoxically worsened timing deficits rather than mitigating them. One interpretation of these combined results is that the cerebellum is indeed functioning as an internal model and is needed to make appropriate predictions for movement initiation and termination.

This article has been cited by other articles:

				D. L. Harrington, J. L. Zimbelman, S. C. Hinton, and S. M. Rao Neural Modulation of Temporal Encoding, Maintenance, and Decision Processes Cereb Cortex, September 24, 2009; (2009) bhp194v1. [Abstract] [Full Text] [PDF]