This is an exploratory study that will determine and standardize how best to record gastric evoked potentials (GEPs) elicited by a non-invasive method of brain stimulation (Transcranial Magnetic Stimulation, TMS), by optimizing the TMS parameters and cortical sites necessary to evoke GEPs.

The overall goal of this exploratory study is to determine the optimal conditions to elicit gastric evoked potentials (GEPs) with Transcranial Magnetic Stimulation (TMS).

Aim 1: Determine the optimal stimulation parameters and the optimal location for eliciting GEPs in cortical motor areas.

Aim 2: Determine whether various modes of repetitive TMS (rTMS) neuromodulation targeted to GEP hotspots shape gastric motor responses to a water load.

The investigators will record some clinical, demographic, and autonomic data (i.e. EKG) in our enrolled subjects. Secondary analyses will use these variables as covariates to investigate any systematic impact on the measures from Aims 1 and 2.

Inclusion Criteria:

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Exclusion Criteria:

• psychosis or altered cognitive status
• history of head injury, metal in the skull, stroke, or a history of seizures, loss of consciousness or syncope
• implantable devices, such as a pacemaker or nerve stimulator
• current use of antiepileptic medications or current use of the following medications or substances which are known to lower the seizure threshold: Clozapine (Clozaril), Chlorpromazine (Thorazine), amphetamines or methamphetamine, Ecstasy, Ketamine, Angel Dust/PCP, cocaine, or 3 or more alcoholic drinks per day
• pregnancy
• BMI > 30
• history of bariatric surgery such as sleeve gastrectomy or Roux-en-Y gastric bypass
• diabetes
• suffering from a neurodegenerative disorder.

There is no current plan to place participant data into a open-access, shared data repository. However, a data sharing agreement can be made if requested.