An automated method to determine the transcranial magnetic stimulation-induced contralateral silent period.
BACKGROUND
The transcranial magnetic stimulation (TMS)-induced contralateral silent period (CSP) refers to a period of interruption of voluntary muscle activity measured in tonically active muscles. The length of the CSP is generally interpreted to reflect cortical inhibition. The determination of the return of voluntary motor activity is typically accomplished via visual inspection of the electromyography (EMG) waveform and may be subject to inaccuracy on the part of the rater.


OBJECTIVE
To present and evaluate an automated method (AM) to determine the CSP.


METHODS
The CSP of 11 healthy controls was recorded using stimulus intensities 20 and 50% above the resting motor threshold (RMT). The mean CSP duration obtained by the two raters using visual inspection and our automated approach were compared.


RESULTS
The interclass correlation coefficient (ICC) between the two raters and the AM was 0.99 at 150% of RMT and was 0.97 at 120% of RMT. The level of pre-stimulus EMG amplitude and sampling rate did not affect agreement between the AM and more conventional visually guided methods.


CONCLUSIONS
Our study demonstrates that this AM is a simple, objective and reliable approach for CSP determination.


CONCLUSIONS
The CSP is an important neurophysiological measure of cortical inhibition and its determination by our AM provides a more objective and automated approach compared to visually guided methods.
Centre for Addiction and Mental Health, Schizophrenia and Continuing Care Program, University of Toronto, Ontario, Canada.
Zafiris J
ZJ
Daskalakis
Gregory F
GF
Molnar
Bruce K
BK
Christensen
Alexandra
A
Sailer
Paul B
PB
Fitzgerald
Robert
R
Chen
D000328:Adult; D000368:Aged; D001331:Automation / Q000295:instrumentation / Q000379:methods*; D002540:Cerebral Cortex / Q000502:physiology*; D004576:Electromyography / Q000379:methods; D019054:Evoked Potentials, Motor / Q000502:physiology; D005260:Female; D007839:Functional Laterality / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D050781:Transcranial Magnetic Stimulation