Influence on Plasticity of Brain Temperature

Background: - Brain activity changes with changes in body temperature. Brain activity can be studied with a procedure called transcranial magnetic stimulation (TMS). Researchers want to cool the brain through the scalp using a cooling cap. They want to see if cooling changes the brain and body s response to TMS. Objectives: - To look at the effects of cooling on the brain. Eligibility: - Right-handed adults age 18-50 who can abstain from caffeine and tobacco. Design: - Participants will be screened with medical history and physical exam. They will be asked about alcohol use, smoking, and substance abuse. They may take a pregnancy test. They may have a magnetic resonance imaging (MRI) scan of the brain. For MRI, participants lie on a table that slides in and out of a metal tube that takes pictures. - Participants will have 3 outpatient visits. The following procedures will occur at each visit. - Participants will wear a cooling cap for up to 45 minutes. Cool water will flow through the cap. It will feel like an ice pack in a towel. Their core temperature will be monitored. Their temperature will also be measured under their tongue and on scalp, stomach, forearm, and calf. - Participants will have TMS before and after wearing the cap. A brief electrical current will pass through a wire coil held on their scalp. Electrodes that detect muscle movement will be placed on their hand. They will also have repetitive TMS, which uses repeated magnetic pulses. Their wrist will also receive a shock.