The focus of this dissertation was to provide further insight into how the motor system supports the representation of sequences over the course of extensive physical practice. In Experiment 1 (Chapter II), evidence for multiple time scales of long-term sequence learning was investigated using functional magnetic resonance imaging (fMRI) in order to quantify blood oxygenation level-dependant (BOLD) magnitude change over the course of an extensive training regimen. Functional change was measured using a novel methodology that incorporated the repetition suppression (RS) effect, which allowed for the minimization of performance confounds. A substantial portion of the motor system demonstrated decreasing patterns of RS with training, indicating that extensive practice leads to neural efficiency. Moreover, the primary motor cortex (M1) and subcortical targets demonstrated an increase in RS at a slow time scale, indicating that extensive practice also leads to neural specialization.

In Experiment 2 (Chapter III), the differential roles of the left dorsal premotor cortex (PMd) and the supplementary motor area (SMA) during sequence learning were investigated using transcranial magnetic stimulation (TMS). A double-dissociation of sequence production error revealed that the left PMd supports the representation of sequences at a faster time scale, whereas the SMA supports the representation of sequences at a slower time scale. In Experiment 3 (Chapter IV), using fMRI, the neural basis of motor chunking was investigated. Motor chunking supports the integration of the individual sequence elements during learning in order to express newly learned sequences as fluid behaviors. The quantification of motor chunking was handled with a novel multi-trial community detection metric. A regression analysis of trial-wise estimates of motor chunking strength revealed that motor chunking is supported by the sensorimotor putamen.

The results from these experiments are discussed regarding their involvement in the representation of motor sequences over the course of extensive physical practice.