All ETDs from UAB

Advisory Committee Chair

Mary M Boggiano

Advisory Committee Members

Franklin R Amthor

Kevin R Fontaine

Edward Taub

Bulent Turan

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. Possible explanations for the conflicting evidence include: 1) expectation effects arising from discernable real vs. sham tDCS conditions, and 2) uncontrolled individual differences related to the outcome variables. Therefore, we conducted a study that systematically assessed the putative action of tDCS to suppress food craving and eating while controlling for expectation effects and baseline individual differences. N=74 adults were randomized to one of four groups: Told Fake/Got Fake (participants were told they were receiving fake and received fake tDCS), Told Fake/Got Real (told they were receiving fake but received real tDCS), Told Real/Got Fake (told they were receiving real but received fake tDCS), and Told Real/Got Real (told they were receiving real and received real tDCS). All groups were informed that tDCS was known to reduce food craving and eating. For real tDCS, 2 mA of current were delivered for 20 minutes. For fake tDCS, current was delivered only during the first and last minute of the 20-minute session. The anode/cathode was placed over the right/left dorsolateral prefrontal cortex for both tDCS conditions. Participants also completed questionnaires including baseline psychological trait surveys related to impulsivity, eating habits, and suggestibility. Food craving and eating, measured with a food-photo craving task and in-lab eating task, were the outcome variables. Analyses revealed an effect of expectation (Told Real vs. Told Fake) on craving and eating; participants who were Told Real craved (p < 0.01) and ate (p <0.01) less that participants who were Told Fake. There was no effect of tDCS (Got Real vs. Got Fake) on craving or eating; that is, there was no difference between participants who Got Real vs. Got Fake tDCS. These findings were unaltered when baseline individual differences were controlled. Future studies using tDCS must take measures against the powerful influence of expectation evidenced here to truly evaluate the efficacy of tDCS as a tool to understand brain function and treat diseases.

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