Pilot Study of Startle-response Test to Assess Transcranial Direct Current Stimulation-induced Modulation of Hyperphagia in Prader-Willi Syndrome

PWS is characterized by hypotonia, feeding difficulties, developmental delay and failure to
thrive during infancy, and by an insatiable appetite (hyperphagia), rapid weight gain and
obesity in early childhood.

Hyperphagia is one of the most prominent and debilitating features of PWS, and currently no
pharmaceutical drug has been successful in decreasing appetite in such patients.

tDCS is a safe, noninvasive method whereby a weak electric current is directly transmitted
into the brain via external electrodes connected to a 9-volt radio battery. It is based on
decades-old observations that nerve cell firing can be altered by low amplitude direct
current (DC). The researchers in this study believe that tDCS may have a positive impact on
hyperphagia and weight.

In this study, the investigators intend to assess whether the effects tDCS differ between
obese subjects, non-obese subjects, and subjects with Prader-Willi syndrome by measuring the
amplitude and latency of eyeblink startle responses to a set of food- and non-food-related
visual stimuli in all subjects, various hyperphagia questionnaires, and cognitive and
behavioral assessments. It is hypothesized that as a group, subjects with Prader-Willi
syndrome will demonstrate behavioral and psychometric evidence of abnormal food image
processing, craving and associated behaviors relative to our control groups, and this group
may receive potentially beneficial effects from tDCS sessions. Obese subjects are also
predicted to have decreased hyperphagia and food cravings as a result of tDCS.

Inclusion Criteria:

- Healthy individuals and individuals diagnosed with Prader-Willi syndrome

- Provide informed consent to participate in the study

- Body Mass Index (BMI) <25kg/m2 (for non-obese subjects only)

- Body Mass Index (BMI) ≥30kg/m2 (for obese subjects only)

Exclusion Criteria:

- Subject is pregnant at time of enrollment in the study.

- Contraindications to tDCS:

1. metal in the head

2. implanted brain medical devices

- Clinically significant and unstable medical disorders (e.g., uncontrolled diabetes,
uncompensated cardiac issues, heart failure, pulmonary issues, or chronic obstructive
pulmonary disease) as self-reported.

- Clinically significant and unstable psychiatric disorders (e.g., schizophrenia,
schizoaffective disorder, other psychosis, bipolar illness, severe depression) as
self-reported.

- Significant visual impairment, as self-reported

- History of auditory deficiencies, as self-reported

- History of alcohol or substance abuse within the last 6 months as self-reported

- Use of carbamazepine within the past 6 months as self-reported.

- Current use of antidepressants

- History of neurological disorders as self-reported

- History of neurosurgery as self-reported