Brain activation in motor sequence learning - the role of variability in input and output space

Abstract

Cortical excitability may be subject to changes through training and learning. Somatosensory learning can increase cortical excitability in somatosensory cortex, an effect which correlates with learning success. Facilitation of motor cortical exitability has been shown to be positively correlated with improvements in performance in simple motor tasks. Thus cortical excitability may be another marker of learning and use-dependent plasticity. Previous studies focussed on the change in cortical excitability brought about by learning processes, therefore the relation between the native level of cortical excitability on the one hand and brain activation and behavioral parameters on the other is as yet widely unknown. In this study, we explored the role of variability of input (motor cortical excitability) and output (motor behavior) upon involvement of brain regions in a complex motor sequencing task requiring either low or high variability of behavior. Results showed that participants with low cortical excitability had significantly higher BOLD activation in task-relevant brain regions than participants with high cortical excitability in both task conditions of high and low behavioral variability, while there were no differences between these groups in percentage of correct responses and improvisation level. Cortical excitability did not change significantly after learning and training. However, the excitability levels of the two groups, which pre-training were significantly different, converged post-training towards mean values that were statistically non-different. High variability of output recruited an extended network consisting of regions in prefrontal ventromedial and orbitofrontal cortex, anterior cingulate, as well as temporoparietal regions and cerebellum, whereas low variability of output activated predominantly precuneus, insula, hippocampus as well as posterior cingulate regions, cingulate gyrus and caudate.