Coherence Technique in Multisited EMG Writer’s Cramp Signals

We setup an EMG amplifier for multi channel capturing of EMG signal with special reference to Writer's cramp (WC) from the subject having input impedance greater than 100 MegOhm(M ). By using this setup we gathered EMG- EMG data (signals) from WC subjects (diseased conditions) hand muscles: ECR and ECU, FCR and FCU, followed by fifth muscle using a set-of-five innocuous micro-wire-electrodes (50μ) in each-subject. We then assessed coherence and conducted chi-square (χ²) tests on these data in eight subjects of concordant(C) group and 4 subjects of discordant (D) group of right-hand-writing-signal (RHWS) and in left-hand-writing-signal (LHWS)) studied. We compared the difference between flexor-aspect-of-forearm and extensor-aspect-of-intrinsic hand-muscles. This showed significant coherence in both concordant and discordant groups of WC mirror-movements (MMs) in mirror-Dystonia. These observations suggest that the nature of EMG-EMG coherence in dystonic WC may be constrained by the descendingmotor- systems, both in terms of their anatomical-distribution and their frequency-characteristics. In our computation, the coherence showed symmetry along the diagonals in graphs. We thus state that, this study showed significant quantifiable EMG differences in the signals/waveforms seen while writing with the right and left hands between those WC subjects with concordant MMs (C group) versus those with discordant MMs (D group).