Noninvasive stimulation of the central nervous system, including transcranial magnetic stimulation (TMS) and transcranial direct current stimulation (tDCS), has been increasingly used in the investigation of cortical plasticity. The purpose of our study is to understand mechanistically-at the neurophysiological and systems levels-how the brain learns new motor skills. We propose to study the acquisition, consolidation, and retention of motor skill learning in healthy subjects. At the behavioral level, we will use movement kinematics to quantify and characterize movement, which allow us to infer functional strategies used by the brain to reduce movement errors. At a neurophysiological level, we will use TMS to document changes in cortical circuitry, which will allow us to infer neuroplastic changes possibly subserving these strategies. At a systems level, we will enhance motor system excitability using tDCS, which will enable us to infer the contribution of the stimulated area to the motor system's ability to learn new skills.

Inclusion Criteria:

• Right-handed dominance
• Ability to give informed consent

Exclusion Criteria:

• active and/or chronic neurological, psychiatric (including depression), or medical conditions
• psychoactive medication use
• active drug/alcohol dependence or abuse history
• homelessness or other social situation that would preclude consistent visits
• history of head injury (including neurosurgery)
• history of seizure
• inability to comprehend or participate in the procedures involved
• metal in the head (besides in mouth), such as implanted electrodes or devices, shrapnel, surgical clips, or fragments from welding/metalwork
• implanted devices (such as cardiac pacemakers, medical pumps, or intracardiac lines) in the thorax