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Changes in Cortical Potential Associated With Modulation of Peripheral Sympathetic Activity in Patients With Epilepsy

From the Department of Psychology (Y.N.), University of Essex, Wivenhoe Park, Colchester, Essex, UK; Department of Clinical and Experimental Epilepsy (Y.N., J.S.D., M.R.T.), Institute of Neurology, University College London, London, UK; Brighton and Sussex Medical School (H.D.C.), Brighton, East Sussex, UK; Sobell Department of Motor Neuroscience and Movement Disorders (J.C.D.), Institute of Neurology, University College London, London, UK.

Address correspondence and reprint requests to Yoko Nagai, Department of Psychology, University of Essex, Wivenhoe Park, Colchester, Essex CO4 3SQ, UK. E-mail: ynagai{at}essex.ac.uk

Objectives: To examine the immediate and sustained effects of volitional sympathetic modulation, using galvanic skin response (GSR) biofeedback training on cortical excitability in patients with drug-resistant epilepsy.

Methods: Ten patients undertook 12 sessions of GSR biofeedback training over 1 month, during which they were trained to increase sympathetic arousal, using GSR biofeedback. Contingent negative variation (CNV) (a slow cortical potential reflecting cortical arousal and excitability) and the related post imperative negative variation (PINV) were quantified before and after biofeedback treatment.

Results: A significant reduction in CNV amplitude was observed in both the short-term (within the first session, after 10 minutes of GSR biofeedback) and long-term (sustained after 12 training sessions). Specifically, the change in baseline CNV amplitude after the 12 training sessions correlated with a percentage reduction in seizure frequency. Furthermore, changes in baseline amplitude of the PINV also correlated with seizure reduction.

Conclusions: Our findings demonstrate that behavioral enhancement of peripheral sympathetic tone (GSR) is associated with modulation of indices of cortical excitability. Moreover, GSR biofeedback training over repeated sessions was associated with a chronic baseline reduction in slow cortical potentials and concurrent therapeutic improvement.

Key Words: biofeedback • galvanic skin response • contingent negative variation • slow cortical potential • post imperative negative variation • epilepsy

Abbreviations: GSR = galvanic skin response; CNV = contingent negative variation; SCP = slow cortical potential; PINV = post imperative negative variation.