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.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
BASIC_SCIENCE
Masking
SINGLE
Enrollment
30
Anode placed over the OFC and cathode placed over the right primary motor cortex.
University of Calgary
Calgary, Alberta, Canada
Probabilistic Decision Making
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)
Time frame: Before and after a 20-minute tDCS session
Cognitive Control
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).
Time frame: Before and after a 20-minute tDCS session
Food-specific 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).
Time frame: Before and after a 20-minute tDCS session
Delayed discounting
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).
Time frame: Before and after a 20-minute tDCS session
Motor impulsivity
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).
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Time frame: Before and after a 20-minute tDCS session.
Moderation of effect by self-reported measures of impulsivity and dysregulated eating
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)).
Time frame: Before and after a 20-minute tDCS session.