BRAIN STIMULATION: Basic, Translational, and Clinical Research in Neuromodulation
Volume 2, Issue 3 , Pages 168-173, July 2009

Sham transcranial magnetic stimulation using electrical stimulation of the scalp

  • Mark S. Mennemeier, PhD

      Affiliations

    • Department of Neurobiology and Developmental Sciences, University of Arkansas for Medical Sciences, Little Rock, Arkansas
    • Corresponding Author InformationCorrespondence: Mark Mennemeier, PhD, University of Arkansas for Medical Sciences, 4301 W Markham St, #826, Little Rock, AR 72205-7199.
    • ,
  • William J. Triggs, MD

      Affiliations

    • Department of Neurology, University of Florida, Gainesville, Florida
    • ,
  • Kenneth C. Chelette, MS

      Affiliations

    • Department of Neurobiology and Developmental Sciences, University of Arkansas for Medical Sciences, Little Rock, Arkansas
    • ,
  • A.J. Woods, MS

      Affiliations

    • Department of Psychology, The George Washington University, Washington, DC
    • ,
  • Timothy A. Kimbrell, MD

      Affiliations

    • Department of Psychiatry, University of Arkansas for Medical Sciences and Mental Health Service, Central Arkansas Veterans Healthcare System (CAVHS), North Little Rock, Arkansas
    • ,
  • John L. Dornhoffer, MD

      Affiliations

    • Department of Neurobiology and Developmental Sciences, University of Arkansas for Medical Sciences, Little Rock, Arkansas
    • Department of Otolaryngology-Head and Neck Surgery, University of Arkansas for Medical Sciences, Little Rock, Arkansas

Received 10 December 2008; received in revised form 5 February 2009; accepted 5 February 2009. published online 06 April 2009.

Background

Most methods of sham, repetitive transcranial magnetic stimulation (rTMS) fail to replicate the look, sound, and feel of active stimulation in the absence of a significant magnetic field.

Objective/hypothesis

To develop and validate a new method of sham rTMS appropriate for a double-blind, placebo-controlled study with subject crossover.

Methods

The look and sound of active rTMS was replicated using a matched, air-cooled sham TMS coil. Scalp muscle stimulation associated with rTMS was replicated with the use of large rubber electrodes placed over selected muscles. The intensity and pulse width of electrical stimulation necessary to match 1-Hz rTMS was developed in one sample of normal, healthy subjects. The sham technique was validated in back-to-back comparisons with active rTMS in new samples of normal, healthy subjects who were either naïve or experienced with rTMS.

Results

Subjects naïve to TMS could not tell which type of stimulation was active or sham or which was electrical or magnetic. Naïve subjects incorrectly picked sham stimulation as active, when forced to choose, because electrical stimulation felt more focused than magnetic stimulation. Subjects experienced with TMS could correctly identify sham and active stimulation. Experimenters could detect subtle differences between conditions.

Conclusions

This method of sham rTMS closely mimics the look, sound, and feel of active stimulation at 1Hz without creating a significant magnetic field. It is valid for use with naïve subjects and in crossover studies. It can accommodate differences in scalp muscle recruitment at different sites of stimulation, and it could potentially be used with higher frequency stimulation.

Keywords: TMS, rTMS, sham

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 This study was supported by the National Institutes of Health (NIH) National Center for Research Resources Centers of Biomedical Research Excellence (COBRE) Grant number RR20146, National Institute of Neurological Disorders and Stroke NS39348, and National Institute of Child Health and Human Development HD040631, HD055269; and by a Tinnitus Research Consortium Grant-in-Aid An abstract of this study was presented at the third International Conference on TMS and tDCS, October 1-4, Gottingen, Germany.

PII: S1935-861X(09)00010-2

doi:10.1016/j.brs.2009.02.002

BRAIN STIMULATION: Basic, Translational, and Clinical Research in Neuromodulation
Volume 2, Issue 3 , Pages 168-173, July 2009

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