Transcranial magnetic stimulation (TMS) is a noninvasive procedure that utilizes an externally positioned current-carrying coil to induce a transcranial magnetic field and stimulate neurons in superficial regions of the cortex. TMS has been approved by the FDA for several psychiatric disorders, including major depressive disorder and obsessive compulsive disorder; however, despite some clinical successes, the mechanisms responsible for the therapeutic effects are not well understood. TMS stimulation protocols vary widely with frequency, pulse duration, and magnitude of the applied magnetic field, all of which influence the underlying cellular responses.