Defective inhibition and inter‐regional phase synchronization in pianists with musician's dystonia: An EEG study

Abstract

Recent neurophysiological studies have associated focal-task specific dystonia (FTSD) with impaired inhibitory function. However, it remains unknown whether FTSD also affects the inhibition (INH) of long-term overlearned motor programs. Consequently, we investigated in a Go/NoGo paradigm the neural correlates associated with the activation (ACT) and inhibition of long-term overlearned motor memory traces in pianists with musician's dystonia (MD), a form of FTSD, during a relevant motor task under constraint timing conditions with multichannel EEG. In NoGo trials, the movement related cortical potentials showed a positive shift after the NoGo signal related to inhibition and was significantly smaller over sensorimotor areas in musicians with MD. Further, we observed an increase at 850-900 ms in the power of beta oscillations which was significantly weaker for the patient group. The role of the inter-electrode phase coupling in the sensorimotor integration of inhibitory processes turned out to be the most relevant physiological marker: the global phase synchronization during INH exhibited an increase between 230 and 330 ms and 7-8 Hz, increase which was significantly smaller for pianists with MD. This effect was due to a weaker phase synchronization between the supplementary motor cortex and left premotor and sensorimotor electrodes in patients. Thus, our findings support the hypothesis of a deficient phase coupling between the neuronal assemblies required to inhibit motor memory traces in patients with MD. EMG recorded from the right flexor pollicis longus muscle confirmed that patients with MD had a disrupted INH in NoGo trials.

Aberrant Oscillatory Activity during Simple Movement in Task-Specific Focal Hand Dystonia

“…These findings support the posit that the timing of activity in the motor system is impaired in tspFHD. This data is consistent with an overall observation of aberrant oscillatory power in tspFHD obtained from power analyses of EEG sensor data during both self-paced (Toro et al, 2000; Kristeva et al, 2005) and cued movement (Ruiz et al, 2009). It is likely that impairments in both cortical excitability and intracortical inhibition contribute to these aberrant patterns of activity we identify in our patient sample.…”

EEG oscillatory patterns are associated with error prediction during music performance and are altered in musician's dystonia

“…Thus, the coordination between brain regions and the corresponding large-scale integrationassessed here by the phase synchronization -seems to be altered in MD, even in tasks performed by the healthy non-affected hand. This result is in line with a previous study of cortical function in MD in an overlearned motor task (Herrojo Ruiz et al, 2009b): in MD pianists an altered interregional phase synchronization was detected in the upper theta/lower alpha (7-8 Hz) bands between the neuronal assemblies required to inhibit motor memory traces. Thus, both studies suggest a possible predominance of theta band oscillations to mediate cortical phase interactions among electrode regions.…”

Abnormal Movement Preparation in Task-Specific Focal Hand Dystonia

“…This argues for abnormalities of an established motor program in task-specific dystonia. On the cortical level, the neural correlates of such abnormalities could be a loss of inhibitory function, as observed intracortically prior to movements in focal hand dystonia [3], or during suppression of motor programs in a Go/NoGo trial in musicians’ dystonia [51]. …”