 The broad goal of the current project is to determine the specific effects of AEDs on cognitive function and driving performance. To address this goal we will assess driving performance and cognitive abilities in neurologically normal volunteers taking phenytoin Dilantin, the most commonly prescribed AED. Effects of phenytoin on driving performance and cognition will be addressed in a randomized, double-blind, placebo-controlled, crossover study. Driver cognition will be assessed using a battery of neuropsychological tests. Driving performance will be objectively assessed in all participants on standardized tasks enacted in a state-of-the-art driving simulator. Our 3 Specific Aims are: 