Abstract
Converging evidence suggest that motor training is associated with early and late changes of the cortical motor system. Transcranial magnetic stimulation (TMS) offers the possibility to study plastic rearrangements of the motor system in physiological and pathological conditions. We used TMS to characterize long-term changes in upper limb motor cortical representation and interhemispheric inhibition associated with bimanual skill training in pianists who started playing in an early age. Ipsilateral silent period (iSP) and cortical TMS mapping of hand muscles were obtained from 30 strictly right-handed subjects (16 pianists, 14 naïve controls), together with electromyographic recording of mirror movements (MMs) to voluntary hand movements. In controls, motor cortical representation of hand muscles was larger on the dominant (DH) than on the non-dominant hemisphere (NDH). On the contrary, pianists showed symmetric cortical output maps, being their DH less represented than in controls. In naïve subjects, the iSP was smaller on the right vs left abductor pollicis brevis (APB) indicating a weaker inhibition from the NDH to the DH. In pianists, interhemispheric inhibition was more symmetric as their DH was better inhibited than in controls. Electromyographic MMs were observed only in naïve subjects (7/14) and only to voluntary movement of the non-dominant hand. Subjects with MM had a lower iSP area on the right APB compared with all the others. Our findings suggest a more symmetrical motor cortex organization in pianists, both in terms of muscle cortical representation and interhemispheric inhibition. Although we cannot disentangle training-related from preexisting conditions, it is possible that long-term bimanual practice may reshape motor cortical representation and rebalance interhemispheric interactions, which in naïve right-handed subjects would both tend to favour the dominant hemisphere.
Highlights
Plasticity represents the ability of the central nervous system to react to physiological and pathological events, occurring during normal development, environmental stimuliPLOS ONE | DOI:10.1371/journal.pone.0157952 June 23, 2016Motor Cortical Plasticity in Piano PlayersAbbreviations: Transcranial magnetic stimulation (TMS), transcranial magnetic stimulation; iSP, Ipsilateral silent period; DH, dominant hemisphere or hand; NDH, than on the non-dominant hemisphere or hand; MMs, mirror movements; fMRI, functional magnetic resonance imaging; MEPs, Motor evoked potentials; APB, from abductor pollicis brevis; ADM, adductor digiti minimi; ECR, extensor carpi radialis; Nine Hole Peg Test (NHPT), nine hole peg test; EMG, electromyogram; RMT, resting motor threshold; CoG, centre-of-gravity; AI, asymmetry index.and pathological processes[1]
Functional magnetic resonance imaging studies have demonstrated lower ipsilateral motor cortex activation during unilateral movement [10, 11] and reduced recruitment of motor association areas during bimanual coordination [12] in piano players compared to naïve subjects
We considered differences in n-iSParea, AI-NHPT, AI-Finger tapping (FT), AI-maparea-AI iSPduration and AI-iSParea according to the occurrence or not of MMs subjects using Mann-Whitney test
Summary
Plasticity represents the ability of the central nervous system to react to physiological and pathological events, occurring during normal development, environmental stimuli (i.e. learning)PLOS ONE | DOI:10.1371/journal.pone.0157952 June 23, 2016Motor Cortical Plasticity in Piano Playersand pathological processes[1]. Functional magnetic resonance imaging (fMRI) studies have demonstrated lower ipsilateral motor cortex activation during unilateral movement [10, 11] and reduced recruitment of motor association areas (such as premotor cortex, cerebellum, prefrontal or basal ganglia) during bimanual coordination [12] in piano players compared to naïve subjects. These data have been interpreted as the result of a long lasting change in the functional properties and connectivity in sensorimotor cortex after extensive hand training [13, 14]. Neurophysiological changes occurring in the motor representations after long-term bimanual skilled learning are, instead, still largely unknown
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