Transcranial Direct Current Stimulation for Impulsivity and Food-related Impulsivity in Obesity (tDCS)

Effect of Transcranial Direct Current Stimulation (tDCS) Applied Over the Orbitofrontal Cortex on Impulsivity and Decision Making in Obese Subjects

In this study the investigators aim to assess whether transcranial direct current stimulation (tDCS; a safe non-invasive method for modulating the activity of specific brain regions) when applied over the orbitofrontal cortex (OFC) is able to modulate impulsivity in obese participants.

In this single-blind, sham controlled study, the investigators will assess whether transcranial direct current stimulation (tDCS; a safe non-invasive method for modulating the activity of specific brain regions) when applied over the orbitofrontal cortex (OFC) is able to modulate impulsivity in obese volunteers. The investigators hypothesize that tDCS applied to the OFC, in comparison to sham tDCS, will significantly reduce impulsivity and enhance decision making as measured by computerized neurocognitive tasks. For this study the investigators will enroll 30 obese individuals aged 18-65 years. Participants will be assessed with a battery of computerized tasks as well as self-reported questionnaires on eating, impulsivity, mood and anxiety. Assessments will be carried out before, during, and after a single 20-minute 2mA tDCS session.

2mA will be applied for 20 minutes with the tDCS anode applied to the left OFC and Cathode applied to the right primary motor cortex.

Current will be ramped up for 30s followed by a 30s ramp down to mimic the physical sensation of stimulation and habituation. The anode placed over the left OFC and cathode placed over the right primary motor cortex.

Net score of the Iowa Gambling Task The net score ranges from -20 to 30. Higher values represent a better outcome (i.e., enhanced decision-making)

Interference index in the Stroop Color-word Task. Interference index is the reaction time computed between the presentation of the stimulus and the response of the participant. It typically ranges from 0 to 300 millisecond, with smaller values of reaction time indicate better outcome (i.e., better cognitive control).

The interference index in the Food-Stroop Color-Word test. Interference index is the reaction time computed between the presentation of the stimulus and the response of the participant. It typically ranges from 0 to 300 millisecond, with smaller values of reaction time indicate better outcome (i.e., better Food-specific cognitive control).

The discount rate for delayed monetary rewards. This rate is quantified by the hyperbolic discounting function using the following equation: V = A/(1+kD), where A presents the value of the delayed reward A at delay D, and k is a free parameter that determines the discount rate, with higher values of k indicate worse outcome (i.e., greater discounting of rewards as a function of time).

The stop-signal reaction time in the Stop-Signal Task. The stop signal reaction time ranges from 50 to 250, where greater values represent worse outcome (i.e, increased motor impulsivity).

Individuals with high levels of impulsivity, impulsive eating, binge eating, self-reported food addiction will show greater moderation by tDCS on our primary and secondary outcomes. Barrat's impulsiveness scale-11 with a range of scores from 0 to 120, with higher scores indicating greater impulsivity. Reward-based eating drive scale-13 with a range of scores from 0 to 54, with higher scores indicating greater uncontrolled eating. Binge eating scale with a range of scores from 0 to 46: minimal binge eating ( >17), moderate binge eating (18-26), and severe binge eating (<27)). Yale Food Addiction Scale with a range of symptom severity from 0 to 7: mild (2-3 symptoms), moderate (4-5 symptoms), severe (6 or more symptoms)).

Inclusion Criteria: Men or Women aged 18 to 65 have body mass index of 35 or above have had no recent change in medications in the 2 weeks prior participating in the study able to fast for 4 hours prior participating in the study Exclusion Criteria: Active Substance use disorder Active Suicidal ideation Psychoactive Medication Past or current Gambling disorder Past or current Anorexia Past or current Bulimia Nervosa Past or current Psychosis Visual impairments preventing performance of the neuropsychological tasks Epilepsy Traumatic Brain Injury Stroke Neurological disorder affecting motor functions (Parkinsons, Huntington's, etc) Previous participation in tDCS research/treatment

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