 Design. Subjects will be assigned to either of two groups, with each group receiving one of the following drugs; carbamazepine CBZ, and lamotrigine LTG. Measures of cortical excitability will be performed using TMS in various drug treatment phases: at baseline before drug intake; during the AED induction period once a day for the first 5 days, after 12 days of drug intake at the maximum dose during steady state; and 3, 7, and 14 half-lives after, and finally three weeks after abrupt drug withdrawal. Blood sampling for drug levels will be performed at each TMS study. 