Hoeft, Fumiko and Wu, Daw-An and Hernandez, Arvel and Glover, Gary H. and Shimojo, Shinsuke (2008) Electronically Switchable Sham Transcranial Magnetic Stimulation (TMS) System. PLoS ONE, 3 (4). e1923. ISSN 1932-6203 http://resolver.caltech.edu/CaltechAUTHORS:HOEplosone08
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Transcranial magnetic stimulation (TMS) is increasingly being used to demonstrate the causal links between brain and behavior in humans. Further, extensive clinical trials are being conducted to investigate the therapeutic role of TMS in disorders such as depression. Because TMS causes strong peripheral effects such as auditory clicks and muscle twitches, experimental artifacts such as subject bias and placebo effect are clear concerns. Several sham TMS methods have been developed, but none of the techniques allows one to intermix real and sham TMS on a trial-by-trial basis in a double-blind manner. We have developed an attachment that allows fast, automated switching between Standard TMS and two types of control TMS (Sham and Reverse) without movement of the coil or reconfiguration of the setup. We validate the setup by performing mathematical modeling, search-coil and physiological measurements. To see if the stimulus conditions can be blinded, we conduct perceptual discrimination and sensory perception studies. We verify that the physical properties of the stimulus are appropriate, and that successive stimuli do not contaminate each other. We find that the threshold for motor activation is significantly higher for Reversed than for Standard stimulation, and that Sham stimulation entirely fails to activate muscle potentials. Subjects and experimenters perform poorly at discriminating between Sham and Standard TMS with a figure-of-eight coil, and between Reverse and Standard TMS with a circular coil. Our results raise the possibility of utilizing this technique for a wide range of applications.
|Additional Information:||© 2008 Hoeft et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Received: December 2, 2007; Accepted: February 29, 2008; Published: April 9, 2008. We thank Professors John D.E. Gabrieli (MIT) and Allan L. Reiss (Stanford) for support throughout the study. Author Contributions: Conceived and designed the experiments: SS FH. Performed the experiments: DW FH AH. Analyzed the data: FH AH GG. Wrote the paper: SS DW FH GG. Funding: This study was funded by the National Science Foundation under BCS-0305276 and BCS-0305866. The sponsors did not play any role in the study besides providing funding. Competing interests: The authors have declared that no competing interests exist.|
|Official Citation:||Hoeft F, Wu D-A, Hernandez A, Glover GH, Shimojo S (2008) Electronically Switchable Sham Transcranial Magnetic Stimulation (TMS) System. PLoS ONE 3(4): e1923. doi:10.1371/journal.pone.0001923|
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|Deposited On:||02 May 2008|
|Last Modified:||26 Dec 2012 10:00|
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