All ETDs from UAB

Advisory Committee Chair

Mary M Boggiano

Advisory Committee Members

Christianne Strang

Edward Taub

Merida M Grant

Document Type

Dissertation

Date of Award

2018

Degree Name by School

Doctor of Philosophy (PhD) College of Arts and Sciences

Abstract

Transcranial direct current stimulation (tDCS) is a neuromodulation technique with promise to improve numerous diseases, but results are inconsistent. A strong candidate explanation for conflicting evidence is that imbalances in expectation effects arise because participants frequently discern full-session current in “real” tDCS from mostly absent current in “fake” tDCS (sham, or control) conditions. Therefore, we conducted a study to test a better control procedure. The real tDCS condition targeted dorsolateral prefrontal cortex (DLPFC) with a right-anode/left-cathode montage expected to suppress food craving and eating. The control targeted sensorimotor cortex with a left-anode/right-cathode montage. Twenty-eight adults with overweight or obesity body mass indexes (BMIs) were informed that tDCS might decrease, increase, or have no effect on craving and eating. Both conditions delivered 2 mA of current for 20 minutes. Demographics, BMI, and baseline trait scores related to impulsivity, suggestibility, and eating-related traits and behaviors were obtained. Food photo ratings and in-lab eating measured craving and eating, respectively. Three original questionnaires were used: The Stimulation-Induced Changes in Eating Perception (SICEP) assessed perceived eating-related changes after stimulation; the Physical Sensations Sheet (PSS) determined types, intensities, and frequencies of sensations experienced during stimulation; and the Real vs. Sham Interview (RSI) assessed whether participants believed both conditions were real, fake, or one real and one fake, along with reasons for their guesses. Analyses found no main effects of condition on craving, amount consumed, perception of changes in eating, or sensations. However, compared to the DLPFC, the sensorimotor control condition reduced craving when BMI and some baseline traits were controlled, and increased perceived reflex-like reaching for food. Further, 50% of participants guessed both conditions were real and 50% guessed one real/one fake. Among the latter, odds of correctly distinguishing conditions not differ from chance. Combined, these results indicate that sensorimotor tDCS may be an improved control condition for DLPFC applications, and that stimulating an alternate site may generally be preferable to the traditional tDCS sham method. Results also question the effectiveness of DLPFC stimulation in suppressing craving and eating. Adoption of the new control type should improve consistency across tDCS studies and clarify tDCS’ utility.

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