Chilling the brain: scientists probe Temperature's role in brain plasticity

Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.

* INCLUSION CRITERIA: Main Study: To be eligible for this research study participants must: * Be between 18 and 50 years of age. * Be right-handed. * Able to abstain from food or drinks containing caffeine 24 hours before the last 3 session visits. The screening visit does not require the ability to abstain from food or drinks containing caffeine. * Able to abstain from tobacco on the day of the last three session visits. The screening visit doesn t require the ability to abstain from tobacco. Sub-study: Phase-triggered paired associative stimulation (PAS) * Males and females between 18 and 35 years of age. * Subjects must be able to give written informed consent prior to participation in this study. EXCLUSION CRITERIA: Main Study: Participants will be excluded from this research study if they: * Are taking medications of the following classes: antidepressants, anxiolytics, anticonvulsants, antipsychotics, antiparkinson, hypnotics, stimulants, and antihistamines. * Have a heart rate that exceeds 100 bpm (resting tachycardia). * Have a history of psychiatric condition(s). * Have a neurologic disorder such as a history of brain tumor, stroke, central nervous system infection, epilepsy, cerebrovascular disease, dementia, head trauma, or increased intracranial pressure. * Have surgically or traumatically implanted metallic foreign bodies such as, pacemakers, medication pumps, implanted hearing aids, defibrillators, metal plates in the skull or metal implants in the skull or eyes (other than dental fillings), intracardiac lines, or any other condition/device that might be physically hazardous during TMS or magnetic resonance imaging (MRI), or might distort the images. * Are unable to lie flat on back for up to 1 hour. * Have claustrophobia or a feeling of discomfort from being in small, enclosed spaces of enough severity to prevent MRI scanning. * Are pregnant or have a positive pregnancy test before the research procedure due to the risks associated with MRI scans and TMS. * Have abnormal findings in clinical MRI that we will do during the screening visit. * Have any abnormal or focal finding on the neurological exam. * Have a known hearing loss. * Have an alcohol or substance abuse problem, as determined by the Alcohol, Smoking and Substance Abuse Screening Test (ASSIST). * Have sensitivity to coldness. (main experiment only, not an exclusion for the sub-study which does not utilize cooling) * NIMH employees and staff and their immediate family members will be excluded from the study per NIMH policy. Sub-study: Phase-triggered paired associative stimulation (PAS) * Individuals taking medication that, in the opinion of the investigator, significantly lowers seizure threshold. * Have a history of psychiatric condition(s). * Have a neurologic disorder such as a history of brain tumor, stroke, central nervous system infection, epilepsy, cerebrovascular disease, dementia, head trauma, or increased intracranial pressure. * Have abnormal findings in MRI that will be conducted during screening or prior to TMS under the current protocol * Are pregnant or have a positive pregnancy test before the beginning of the study due to the risks associated with TMS. * Subjects who have hearing loss that has been clinically evaluated and diagnosed. * Any implant, prosthesis or other permanent alteration of the body that, in the opinion of the investigator, would be unsafe with TMS or that would produce an artifact that would compromise the integrity of data. * Positive test for HIV. * Have an alcohol or substance abuse problem. * NIMH employees and staff and their immediate family members will be excluded from the study per NIMH policy.