Clockwork Dysfunctions: Impaired Use of Temporal Structure in Cerebellar and Basal Ganglia Lesion Patients

Abstract

Contrasting with the distinct psychological sense of time in humans, physiological correlates underlying this impression are not readily observable. Classical motor structures such as the cerebellum and the basal ganglia are among the prime candidates for the neural implementation of dedicated temporal processing mechanisms, specialized in generating representations of the temporal structure of events. Consequently, circumscribed structural damage to these brain areas is expected to alter the use of temporal structure in motor and non-motor behavior. A crucial aspect of this general capacity is temporal extrapolation, i.e., the ability to use the temporal structure of past events to predict when a future event will happen and to adapt behavior accordingly. Such predictive adaptation to temporal structure provides the opportunity to optimize behavior on the basis of perceived regularity in temporal structure. Against this background, a series of experiments was conducted, taking advantage of the high spatial resolution of structural magnetic resonance imaging and the high temporal resolution of event-related potentials of the electroencephalogram. Patients with focal lesions of either the cerebellum or the basal ganglia and matched controls performed tasks, which require precise production and/or perception of temporal structure. Production of temporal structure was tested in the context of sensorimotor synchronization with auditory pacing sequences containing a tempo change. Measures of interest related to the general efficiency of the tapping performance, to error correction in response to the tempo change, as well as to the awareness of the change. Perception was tested in the context of auditory deviance processing as a function of temporal predictability, i.e., by means of “oddball sequences”, consisting of tones that were presented with regular or irregular temporal structure. Measures of interest related to qualitative differences in early and later stages of deviance processing, as indexed by event-related potentials (P50, P300). In comparison to controls, the performance of the patients diverges systematically on several of these measures, suggesting impaired use of temporal structure. Taken together, the results differentiate the specific contributions of the cerebellum and the basal ganglia to the processing of temporal structure, most likely within an integrative dedicated temporal processing network.