Effects of Repetitive tDCS on ad Libitum Smoking Behavior: EMA and EEG Study

Bilateral (left cathodal/ right anodal) transcranial Direct Current Stimulation (tDCS) over the dorsolateral prefrontal cortex (DLPFC) seems to reduce craving and to increase the time till smoking the first cigarette after the intervention. The current study explores whether actual cigarette consumption decreases after repetitive tDCS. Cigarette consumption and craving will therefore be measured by means of EMA, before (at baseline), during and after multiple tDCS sessions, and at 3 months follow-up. To study the working mechanism behind the effects of tDCS, electrophysiological responses (ERPs) and behavioral measures of cognitive control functioning will be taken into account at baseline, one day after the last tDCS session and at three months follow up. We hypothesize that cigarette consumption will decrease after repetitive tDCS, and that this effect is associated with better cognitive control functioning.

The proposed experiment is a double-blind randomized placebo-controlled trial. 60 smokers will be randomly assigned to two conditions, namely tDCS or sham (placebo). Participants will receive real tDCS or sham for three days in one week. The interventions contain twice daily sessions for 13 minutes with an interval of 20 min. Moreover, on the first treatment day and the day after the treatment week, participants complete a number of questionnaires, and perform two psychological tasks (a gambling task and the Go/NoGo task) to measure cognitive control functioning (e.g. risky decision making and inhibitory control respectively). During these tasks, event-related potentials will be recorded by means of EEG. After three months, participants are asked to return to fill out the same questionnaires and perform the same psychological tasks as before, to measure the lasting effect of tDCS. During this last session, event-related potentials will also be recorded. In addition, carbon monoxide levels will be measured on all days where subjects perform the tasks. EMA: For three weeks, starting the week before tDCS treatment, participants are asked to log every cigarette before they smoke one. During these weeks, participants complete EMA questionnaires on their mobile phone about cigarette consumption, craving, and affect that will take approximately 5 minutes. The EMA questionnaire will be presented four times daily on a quasi-random basis. Finally, during end-of-day assessments participants have the possibility to indicate any missed cigarettes. At three months follow-up, participants are asked to undergo the same EMA procedure for one more week, to study the lasting effects of tDCS.

Smoking, EMA, ERPs, tDCS, Cigarette consumption, Inhibitory control, Reward processing, Tobacco addiction, Craving, electrophysiological

This group will receive bilateral tDCS (left cathodal/right anodal) over the DLPFC. The stimulation will take place two times daily for 13 minutes with a rest interval of 20 minutes for three days in one week.

The control group receives sham, for which the stimulator will be gradually turned off after 30 seconds.

The mean number of cigarettes will be measured at three months follow-up by means of Ecological Momentary Assessments (EMA). This means that participants are asked to report every cigarette they smoke at the moment they're about to smoke it with an app on their mobile phone. Participants do this during the week before the last EEG session at three months follow-up.The mean number will be calculated over this week

The mean number of cigarettes will be measured at one week after the last tDCS session by means of Ecological Momentary Assessments (EMA). This means that participants are asked to report every cigarette they smoke at the moment they're about to smoke it with an app on their mobile phone. Participants do this for one week starting from the last tDCS session. The mean number will be calculated over this week

Participants receive 4 prompts a day in the app on the smartphone to fill out questions about craving for 1 week starting the week before the last EEG session at three months follow-up

Participants receive 4 prompts a day in the app on the smartphone to fill out questions about affect for 1 week starting the week before the last EEG session at three months follow-up

Participants receive 4 prompts a day in the app on the smartphone to fill out questions about craving for 1 week starting the day after the last tDCS session

Participants receive 4 prompts a day in the app on the smartphone to fill out questions about affect for 1 week starting the day after the last tDCS session

Measured with the two choice gambling task. After the choice (high/low risk) is made, participants receive feedback (either they lose or win). The Feedback Related Negativity (FRN) will be measured after feedback by means of EEG.

Measured with the two choice gambling task. After the choice (high/low risk) is made, participants receive feedback (either they lose or win). The reward related P300 will be measured 300-500 ms after feedback by means of EEG.

Wrong responses to Go and NoGo trials in the Go/NoGo task will be used to assess the error related negativity (ERN)

Number of cigarettes (and craving) a day starting on the first tDCS day until one week after the last tDCS intervention

Inclusion Criteria: Currently smoking 10 or more cigarettes a day The ability to speak, read, and write in Dutch at an eight-grade literacy level Exclusion Criteria: The current abuse of a substance other than nicotine or caffeine History of neurological or psychiatric disorders Any contraindication for electrical brain stimulation procedures such as electronic implants or metal implants Pregnancy or breast-feeding In the process of quitting smoking

Verveer I, Remmerswaal D, van der Veen FM, Franken IHA. Long-term tDCS effects on neurophysiological measures of cognitive control in tobacco smokers. Biol Psychol. 2020 Oct;156:107962. doi: 10.1016/j.biopsycho.2020.107962. Epub 2020 Sep 23.

Verveer I, Remmerswaal D, Jongerling J, van der Veen FM, Franken IHA. No effect of repetitive tDCS on daily smoking behaviour in light smokers: A placebo controlled EMA study. PLoS One. 2020 May 22;15(5):e0233414. doi: 10.1371/journal.pone.0233414. eCollection 2020.