Different stimulation frequencies alter synchronous fluctuations in motor evoked potential amplitude of intrinsic hand muscles—A TMS study

Martin V. Sale, Nigel C. Rogasch, Michael A. Nordstrom

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3 Citations (Scopus)


The amplitude of motor-evoked potentials (MEPs) elicited with transcranial magnetic stimulation (TMS) varies from trial-to-trial. Synchronous oscillations in cortical neuronal excitability contribute to this variability, however it is not known how different frequencies of stimulation influence MEP variability, and whether these oscillations are rhythmic or aperiodic. We stimulated the motor cortex with TMS at different regular (i.e. rhythmic) rates, and compared this with pseudo-random (aperiodic) timing. In 18 subjects, TMS was applied at three regular frequencies (0.05 Hz, 0.2 Hz, 1 Hz) and one aperiodic frequency (mean 0.2 Hz). MEPs (n = 50) were recorded from three intrinsic hand muscles of the left hand with different functional and anatomical relations. MEP amplitude correlation was highest for the functionally related muscle pair, less for the anatomically related muscle pair and least for the functionally-and anatomically-unrelated muscle pair. MEP correlations were greatest with 1 Hz, and least for stimulation at 0.05 Hz. Corticospinal neuron synchrony is higher with shorter TMS intervals. Further, corticospinal neuron synchrony is similar irrespective of whether the stimulation is periodic or aperiodic. These findings suggest TMS frequency is a crucial consideration for studies using TMS to probe correlated activity between muscle pairs.

Original languageEnglish
Article number100
JournalFrontiers in Human Neuroscience
Issue numberMAR2016
Publication statusPublished or Issued - 7 Mar 2016
Externally publishedYes


  • Abductor digiti minimi
  • Abductor pollicis brevis
  • Cortical oscillations
  • First dorsal interosseous
  • Motor cortex
  • Motor-evoked potential
  • Transcranial magnetic stimulation

ASJC Scopus subject areas

  • Neuropsychology and Physiological Psychology
  • Neurology
  • Psychiatry and Mental health
  • Biological Psychiatry
  • Behavioral Neuroscience

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