Activating and Identifying Neural Responses to Social Rejection: a Combined tDCS and fMRI Study

Aim 1: To test the behavioral effects of tDCS during social rejection. The first step will be to obtain behavioral effects of transcranial direct current stimulation (tDCS) during social rejection without functional magnetic resonance imaging (fMRI). Whereas previous studies used "Cyberball" (a computerized ball-tossing game that simulates social exclusion), we will use the Social Feedback Task. This task was created by Dr. Hsu to be more ethologically-relevant, has been shown to sustain negative moods during rejection and activates the right ventral lateral prefrontal cortex (rVLPFC) (preliminary fMRI data from 50 healthy controls in Dr. Hsu's previous study). Anodal tDCS will be applied over the right or left VLPFC to measure changes in mood during rejection and neutral conditions. Depending on results, alternate regions in separate subjects may also be stimulated: dorsolateral prefrontal cortex, insula, anterior cingulate cortex, pre-supplementary, and supplementary motor area [all regions may be right or left hemisphere]. All of these regions have been shown to be involved in emotion regulation. Questionnaires will be given before, during, and after the task to assess cognitive and emotional states.

Aim 2: To identify neural pathways regulating negative moods during social rejection, using tDCS for activation and fMRI for assessment. Using a cross-over, sham-controlled design similar to previous tDCS+fMRI studies, we will measure the effects of anodal tDCS over the right or left VLPFC on neural activity and negative mood during rejection and neutral conditions. Alternate regions in separate subjects may also be stimulated including the dorsolateral prefrontal cortex, insula, anterior cingulate cortex, pre-supplementary, and supplementary motor area [all regions may be right or left hemisphere]. All of these regions have been shown to be involved in emotion regulation.

Inclusion criteria

• Healthy males or females between 18 and 25 years old
• No diagnosis on Axis I by Structured Clinical Interview for Diagnostic and Statistical Manual of Mental Disorders IV. No current, or within the past 5 years.
• Not currently in a romantic relationship
• Ability to understand and follow instructions and oriented to name, time, and place.
• No additional neurologic or psychiatric disorders
• No current use of psychotropic drugs or during past 3 months (except marijuana and alcohol)
• No current use of marijuana or during past 3 weeks
• Not currently abusing alcohol
• No history of alcohol or drug dependence within past 5 years
• A negative urine pregnancy and toxicology screen. Verbal affirmation will be obtained (i.e., "not pregnant" and "not currently using psychotropic drugs or during the past 3 months") during the Screening Visit (Day 1). Urine screen will be obtained on Days 2 and 3. If subject reports that there is a "possibility that she is pregnant" on Day 1 (Screening Visit) a urine pregnancy screen will be performed on that day.
• (Women): If stopped or started oral contraceptives recently, at least 60 days on/off oral contraceptives.

Exclusion criteria

• Left-handed or ambidextrous
• Metallic dental implants
• Metallic objects in the brain/skull
• Medical device implants
• Implanted electronic devices
• History of seizures
• History of strokes
• Unexplained loss of consciousness
• Frequent or severe headaches or neck pain
• Clinically significant, uncontrolled liver, kidney, cardiac, or pulmonary disease
• Terminal medical diagnosis consistent with survival < 1 year
• Pregnancy; childbirth or miscarriage within 6 months, breastfeeding within 6 months of recruitment
• Serious mental impairment. Mini mental state exam of < 23/30
• Chronic skin disease
• Previous experience with transcranial direct current stimulation (tDCS)
• Regular tobacco use or tobacco use within past month
• If using hormonal birth control, taking progestin-only pills (e.g., Cerazette, Ovrette), or Intrauterine devices (Mirena, Skyla), since progestin-only birth controls are more likely to cause mood swings.

Addition Exclusion Criteria for participating in fMRI:

• Metal anywhere in the body
• Weight over 250 pounds, or girth size incompatible for scanner bore.