Primary sensorimotor areas' connectivity in focal task-specific hand dystonia

Abstract

Event Abstract Back to Event Primary sensorimotor areas' connectivity in focal task-specific hand dystonia Jean M. Melgari1, Filippo Zappasodi2*, Camillo Porcaro3, Leo Tomasevic4, Emanuele Cassetta5, Paolo M. Rossini1 and Franca Tecchio6, 7 1 Campus Biomedico University, Department of Neurology, Italy 2 G. D Annunzio University, Department of Clinical Sciences and Bioimaging , Italy 3 University of Birmingham, School of Psychology and Birmingham University Imaging Centre, United Kingdom 4 ISTC, Italy 5 Isola Tiberina, AFaR, Fatebenefratelli hospital, Italy 6 Università Campus Biomedico, Neurologia Clinica, Italy 7 Isola Tiberina, CNR-ISTC, Unità MEG, Ospedale Fatebenefratelli, Italy Starting from the growing evidence of a possible sensorimotor integration impairment in focal task-specific hand dystonia, we segregated activities of primary sensory (S1) and primary motor (M1) cortices aiming to investigate their functional cross-talk during non-dystonia inducing sensorimotor tasks. Magnetoencephalographic (MEG) and opponens pollicis electromyographic (EMG) activities were acquired at rest and during a simple isometric contraction performed either alone or in combination with median nerve stimulation. The task was performed bilaterally both in 8 patients suffering from focal task-specific hand dystonia and in 8 healthy volunteers. Through an ad-hoc procedure (Functional Source Separation, [1]) distinct sources were identified in S1 (FS_S1) and M1 (FS_M1) devoted to the hand control. The spectral properties and the functional coupling (coherence) between the two sources were assessed in the three Rolandic most reactive frequency bands (alpha [8, 12] Hz, beta [13, 32] Hz and gamma [33, 45] Hz). In dystonic patients with respect to controls we found: i) higher MEG-EMG coherence, ii) which reduced much less during galvanic stimulation; iii) that the cortical component including contributions from sensory inhibitory and motor structures was reduced and iv) much more inhibited during movement; v) higher power for both FS_S1 and FS_M1 in the gamma band and vi) lower FS_S1-FS_M1 coherence in the same band. The simultaneous occurrence of an increased cortico-muscular coherence, in presence of a reduced M1 responsiveness to the sensory inflow, indicate an unbalance of the fronto-parietal functional impact onto M1, as also suggested by the lack of FS_S1-FS_M1 coherence.