AUTHOR=Royter Vladislav , Gharabaghi Alireza 

TITLE=Brain State-Dependent Closed-Loop Modulation of Paired Associative Stimulation Controlled by Sensorimotor Desynchronization

JOURNAL=Frontiers in Cellular Neuroscience

VOLUME=10

YEAR=2016

URL=https://www.frontiersin.org/journals/cellular-neuroscience/articles/10.3389/fncel.2016.00115

DOI=10.3389/fncel.2016.00115

ISSN=1662-5102

ABSTRACT=<p><bold>Background</bold>: Pairing peripheral electrical stimulation (ES) and transcranial magnetic stimulation (TMS) increases corticospinal excitability when applied with a specific temporal pattern. When the two stimulation techniques are applied separately, motor imagery (MI)-related oscillatory modulation amplifies both ES-related cortical effects—sensorimotor event-related desynchronization (ERD), and TMS-induced peripheral responses—motor-evoked potentials (MEP). However, the influence of brain self-regulation on the associative pairing of these stimulation techniques is still unclear.</p><p><bold>Objective</bold>: The aim of this pilot study was to investigate the effects of MI-related ERD during associative ES and TMS on subsequent corticospinal excitability.</p><p><bold>Method</bold>: The paired application of functional electrical stimulation (FES) of the extensor digitorum communis (EDC) muscle and subsequent single-pulse TMS (110% resting motor threshold (RMT)) of the contralateral primary motor cortex (M1) was controlled by beta-band (16–22 Hz) ERD during MI of finger extension and applied within a brain-machine interface environment in six healthy subjects. Neural correlates were probed by acquiring the stimulus-response curve (SRC) of both MEP peak-to-peak amplitude and area under the curve (AUC) before and after the intervention.</p><p><bold>Result</bold>: The application of approximately 150 pairs of associative FES and TMS resulted in a significant increase of MEP amplitudes <italic>and</italic> AUC, indicating that the induced increase of corticospinal excitability was mediated by the recruitment of additional neuronal pools. MEP increases were brain state-dependent and correlated with beta-band ERD, but not with the background EDC muscle activity; this finding was independent of the FES intensity applied.</p><p><bold>Conclusion</bold>: These results could be relevant for developing closed-loop therapeutic approaches such as the application of brain state-dependent, paired associative stimulation (PAS) in the context of neurorehabilitation.</p>