SENSORIMOTOR INTEGRATION IN FOCAL TASK-SPECIFIC HAND DYSTONIA: A MAGNETOENCEPHALOGRAPHIC ASSESSMENT F. TECCHIO, a,b * J. M. MELGARI, c F. ZAPPASODI, a,d C. PORCARO, d,e D. MILAZZO, d E. CASSETTA b,d AND P. M. ROSSINI b,c a ISTC-CNR, Unità MEG, Fatebenefratelli Hospital, Dip. Neuroscienze, Osp. Fatebenefratelli, Isola Tiberina 39, 00186 Rome, Italy b Casa di Cura San Raffaele Cassino e IRCCS San Raffaele, Pisana, Italy c Department of Neurology, “Campus Bio-Medico” University, Via Al- varo del Portillo, 200, 00128 Rome, Italy d AFaR, Fatebenefratelli Hospital, Isola Tiberina, 00186 Rome, Italy e ITAB Institute for Advanced Biomedical Technologies, “G. D’Annunzio” University, Chieti, Italy Abstract—To obtain a direct sensorimotor integration as- sessment in primary hand cortical areas (M1) of patients suffering from focal task-specific hand dystonia, magnetoen- cephalographic (MEG) and opponens pollicis electromyo- graphic (EMG) activities were acquired during a motor task expressly chosen not to induce dystonic movements in our patients, to disentangle abnormalities indicating a possible substrate on which dystonia develops. A simple isometric contraction was performed either alone or in combination with median nerve stimulation, i.e. when a non-physiological sensory inflow was overlapping with the physiological feed- back. As control condition, median nerve stimulation was also performed at rest. The task was performed bilaterally both in eight patients and in 16 healthy volunteers. In comparison with results in controls we found that in dystonic patients: i) MEG-EMG coherence was higher; ii) it reduced much less during galvanic stimulation in the hemi- sphere contralateral to the dystonic arm, simultaneously with iii) stronger inhibition of the sensory areas responsiveness due to movement; iv) the cortical component including con- tributions from sensory inhibitory and motor structures was reduced and v) much more inhibited during movement. It is documented that a simultaneous cortico-muscular coherence increase occurs in presence of a reduced M1 responsiveness to the inflow from the sensory regions. This could indicate an unbalance of the fronto-parietal functional impact on M1, with a weakening of the parietal components. Concurrently, signs of a less differentiated sensory hand representation—possibly due to impaired inhibitory mecha- nisms efficiency—and signs of a reduced repertoire of vol- untary motor control strategies were found. © 2008 IBRO. Published by Elsevier Ltd. All rights reserved. Key words: sensorimotor integration, dystonia, cortico- muscular coherence, SEF, magnetoencephalography, MEG. Movement control quality requires continuum functional integration between two activities: the motor areas in- volved in the task programming and execution, and the areas elaborating sensory and proprioceptive information (Terao et al., 1999; Battaglia-Mayer et al., 2003; Scott 2004). Focal dystonia is a disorder characterized by involun- tary, sustained muscle contractions, frequently causing repetitive twisting movements or abnormal postures of a single body part (Fahn et al., 1987, 1998). Dystonia in- volves co-contraction of antagonist muscles that is com- monly worsened during voluntary movement. In the case of task-specific dystonia this pathologic situation occurs only within a specific motor frame (Bressman, 2000). An etiological role of highly articulated, strictly repetitive move- ments, is expected (Byl et al., 1996; Hallett, 2006; Quart- arone et al., 2006). Pathophysiological changes in neuro- nal pools’ balance, mainly reduced efficiency of inhibitory structures (Berardelli et al., 1998; Hallett, 2004), have been reported at various levels of the CNS: motor cortex (Ridding et al., 1995; Byl et al., 1996), sensory cortex (Tinazzi et al., 2003) or sensorimotor integration networks (Abbruzzese and Berardelli, 2003; Quartarone et al., 2006; Murase et al., 2006). In focal dystonia sensory input to a certain area of the body can reduce abnormal contractions in muscles nearby suggesting a role of sensorimotor links in modulating dys- tonia. This pathognomonic characteristic is called “sensory trick” (Berardelli et al., 1998; Abbruzzese et al., 2003; Candia et al., 2003; Zeuner et al., 2002; Tinazzi et al., 2003). In addition to this clinical evidence, a large bulk of data indicated that sensory input can modify dystonia (for a review see Tinazzi et al., 2003). Starting from the growing evidence of sensorimotor integration impairment as a key pathophysiological mech- anism in dystonia, our task in the present study is to discriminate between sensory and motor counterparts at primary cortical level. We will aim to simultaneously assess two aspects: the sensory areas’ excitability modulation due to movement, and the motor area cortico-muscular cou- pling modulation due to an additional non-physiological sensory inflow. A motor task not inducing dystonia was selected in order to disentangle abnormalities indicating a possible substrate on which dystonia develops. We ap- plied a magnetoencephalographic (MEG) experimental procedure previously validated in healthy subjects (Tec- chio et al., 2006). The sensorimotor interaction studied in *Correspondence to: F. Tecchio, ISTC-CNR, Unità MEG, Dip. Neuro- scienze, Osp. Fatebenefratelli, Isola Tiberina 39, 00186 Roma, Italy. Tel: +39-06-6837-382; fax: +39-06-6837-360. E-mail address: franca.tecchio@istc.cnr.it (F. Tecchio). Abbreviations: ANOVA, analysis of variance; BA, Brodmann area; ECD, equivalent current dipole; EMG, electromyographic; M1, primary hand cortical areas; MEG, magnetoencephalographic; MVC, maximal voluntary contraction; OP, opponens pollicis; PSD, power spectral density; SEF, somatosensory evoked field; SM1, sensorimotor primary hand cortical areas. Neuroscience 154 (2008) 563–571 0306-4522/08$32.00+0.00 © 2008 IBRO. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.neuroscience.2008.03.045 563