Dataset Information

Electronically switchable sham transcranial magnetic stimulation (TMS) system.

ABSTRACT: 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.

SUBMITTER: Hoeft F

PROVIDER: S-EPMC2271126 | biostudies-literature | 2008 Apr

REPOSITORIES: biostudies-literature

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Electronically switchable sham transcranial magnetic stimulation (TMS) system.

Hoeft Fumiko F Wu Daw-An DA Hernandez Arvel A Glover Gary H GH Shimojo Shinsuke S

PloS one 20080409 4

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 t ...[more]

PMID: 18398456

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Project description:Daily left prefrontal repetitive transcranial magnetic stimulation (rTMS) over several weeks is an FDA approved treatment for major depression. Although rTMS is generally safe when administered using the FDA guidelines, there are a number of side effects that can make it difficult for patients to complete a course of rTMS. Many patients report that rTMS is painful, although patients appear to accommodate to the initial painfulness. The reduction in pain is hypothesized to be due to prefrontal stimulation and is not solely explained by accommodation to the stimulation.In a recent 4 site randomized controlled trial (using an active electrical sham stimulation system) investigating the antidepressant effects of daily left dorsolateral prefrontal rTMS (Optimization of TMS, or OPT-TMS), the procedural painfulness of TMS was assessed before and after each treatment session. Computerized visual analog scale ratings were gathered before and after each TMS session in the OPT-TMS trial. Stimulation was delivered with an iron core figure-8 coil (Neuronetics) with the following parameters: 10 Hz, 120% MT (EMG-defined), 4 s pulse train, 26 s inter-train interval, 3000 pulses per session, one 37.5 min session per day. After each session, procedural pain (pain at the beginning of the TMS session, pain toward the middle, and pain toward then end of the session) ratings were collected at all 4 sites. From the 199 patients randomized, we had usable data from 142 subjects for the initial 15 TMS sessions (double-blind phase) delivered over 3 weeks (142 × 2 × 15 = 4260 rating sessions).The painfulness of real TMS was initially higher than that of the active sham condition. Over the 15 treatment sessions, subjective reports of the painfulness of rTMS (during the beginning, middle and end of the session) decreased significantly 37% from baseline in those receiving active TMS, with no change in painfulness in those receiving sham. This reduction, although greatest in the first few days, continued steadily over the 3 weeks. Overall, there was a decay rate of 1.56 VAS points per session in subjective painfulness of the procedure in those receiving active TMS.The procedural pain of left, prefrontal rTMS decreases over time, independently of other emotional changes, and only in those receiving active TMS. These data suggest that actual TMS stimulation of prefrontal cortex maybe related to the reduction in pain, and that it is not a non-specific accommodation to pain. This painfulness reduction softly corresponds with later clinical outcome. Further work is needed to better understand this phenomenon and whether acute within-session or over time painfulness changes might be used as short-term biomarkers of antidepressant response.

Dataset Information

Electronically switchable sham transcranial magnetic stimulation (TMS) system.

Publications

Electronically switchable sham transcranial magnetic stimulation (TMS) system.

Similar Datasets

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