Behavioural and neural correlates of sensorimotor timing and error correction

Timing is essential for human movement and cognition and is affected in many psychiatric and neurological disorders. The aim of this thesis was to determine the behavioural and neural correlates of sensorimotor timing and of temporal error correction. Motor timing can be studied using a sensorimotor synchronization (SMS) task. In SMS, timing accuracy is assessed during synchronized finger tapping with a regular pacing stimulus and error correction performance is measured based on responses following induced local timing shifts. Study one addressed the effects of task-related and subject-specific factors on SMS performance and showed that tapping variability was reduced during bimanual SMS, compared with unimanual SMS. Study two examined the role of the primary and pre-motor cortices in SMS using theta burst transcranial magnetic stimulation (TBS). The findings suggested that the left-lateralized pre-motor cortex may play a role in temporal error correction. This hypothesis was tested in study three which confirmed that suppression TBS over the left pre-motor significantly affected error correction responses following supraliminal timing shifts. Study four used functional magnetic resonance imaging (fMRI) to determine the neural correlates of timing and error correction. It was shown that connectivity emerges in a cortico- cerebellar network including the left-lateralized cerebellum and frontal regions during the correction of supraliminal timing shifts. Study five further examined the role of functional connectivity using fMRI and revealed that interhemispheric connectivity between the primary motor cortices was significantly greater during bimanual SMS, compared with unimanual SMS. Lastly, studies six and seven addressed the efficacy of TBS and showed that the local distribution of subarachnoid cerebrospinal fluid can significantly alter TBS-induced stimulation. In the general discussion it is suggested that sensorimotor timing and error correction may be achieved using internal feedforward models in the cerebellum that inform movement initiation controlled by the left pre-motor cortex.