ABSTRACT
This study examined whether a single session of repetitive transcranial magnetic stimulation (rTMS) of the left prefrontal cortex (PFC) would inhibit food cravings in healthy women who endorsed frequent food cravings. Ten participants viewed images of food and completed ratings for food cravings before and after receiving either real or sham rTMS over the left PFC (10 Hz, 100% resting motor threshold, 10 s-on, 20 s-off for 15 min; 3000 pulses). Sham-TMS was matched with real TMS with respect to perceived painfulness of the stimulation. Each participant received both real and sham rTMS in random order and were blind to the condition in a within-subject cross-over design. With an improved sham control condition, prefrontal rTMS inhibited food cravings no better than sham rTMS. The mild pain from the real and sham rTMS may distract or inhibit food craving, and the decreased craving may not be caused by the effect of rTMS itself. Further studies are needed to elucidate whether rTMS has any true effects on food craving and whether painful stimuli inhibit food or other cravings. A sham condition which matches the painfulness is important to understand the true effects of TMS on behaviors and diseases.
ABSTRACT
BACKGROUND: Transcranial magnetic stimulation (TMS) is a relatively noninvasive brain stimulation technology that can focally stimulate the human cortex. One significant limitation of much of the TMS research to date concerns the nature of the placebo or sham conditions used. When TMS pulses are delivered repetitively (especially prefrontal TMS), it is often experienced as painful. Most sham TMS techniques produce identical sounds to active TMS, but they do not cause much, if any, scalp or facial sensation or discomfort. This is a serious problem when investigators are attempting to evaluate the effects of TMS by using traditional sham techniques because of unintended systematic differences between real and sham TMS groups (ie, confounds). As long as traditional approaches to sham TMS are used, the validity of the inferences regarding the efficacy of TMS will be limited. Although some other sophisticated systems have been developed to address these concerns, they tend to be expensive and lack portability. Portability will likely become more and more important as TMS applications expand into different clinical areas (eg, TMS in the postanesthesia care unit after surgery). METHODS: This study describes a portable electrical TMS sham system (eSham system) modeled after the James Long System that was designed to produce similar scalp sensations as real TMS. Preliminary results are presented on 9 healthy adults who received both real and eSham 10 Hz repetitive TMS (rTMS) (at 80%, 100%, and 120% of resting motor threshold) over the prefrontal cortex and rated the sensation quality (pain, tingling, sharpness, piercing, electric, tugging, pinching), tolerability, and location. RESULTS: Real TMS and eSham TMS were rated similarly across all seven sensory dimensions examined. Real and eSham TMS were also rated similarly with respect to tolerability and perceived location of the TMS-induced sensations. CONCLUSIONS: The eSham system may be a simple, affordable, and portable approach to providing convincing sham TMS for future clinical trials. This study provides preliminary evidence supporting the use of the eSham system. Future larger-scale studies are warranted.
