Intracortical inhibition in the human trigeminal motor system

Shapour Jaberzadeh, Sophie L Pearce, Timothy S Miles, Kemal Turker, Michael A Nordstrom

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8 Citations (Scopus)

Abstract

OBJECTIVE: To investigate the presence and features of short-interval intracortical inhibition (SICI) in the human trigeminal motor system. METHODS: Surface electromyogram (EMG) was recorded from left and right digastric muscles in 7 subjects, along with additional experiments with intramuscular EMG in 2 subjects. Focal transcranial magnetic stimulation (TMS) was used to activate the motor cortex of one hemisphere and elicit motor evoked potentials (MEPs) in digastric muscles on each side, at rest and while subjects activated the muscles at 10 maximal EMG. Paired or single TMS pulses were delivered in blocks of trials, while conditioning TMS intensity and interstimulus interval (ISI) were varied. RESULTS: At rest, paired TMS (3-ms ISI) with conditioning intensities 0.8-0.9x active motor threshold (TA) reduced the digastric MEP amplitude to a similar extent bilaterally. Conditioning at 0.5-0.7TA did not significantly reduce the MEP. MEP amplitude was reduced to a similar extent in both digastric muscles by ISIs between 1 and 4 ms (0.8TA). Voluntary bilateral activation of digastric muscles reduced the effectiveness of conditioning TMS compared to the resting state, with no differences between sides. The similarity of the responses in both digastric muscles was not due to EMG cross-talk (estimated to be approximately 10 in surface records and approximately 2 in intramuscular records), as the intramuscular records showed the same pattern as the surface records.
Original languageEnglish
Pages (from-to)1785 - 1793
Number of pages9
JournalClinical Neurophysiology
Volume118
Issue number8
Publication statusPublished - 2007

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