 ObjectiveHypothesis: We propose to use quantitative indices of brain electrical activity and diffusion tensor imaging DTI to characterize the effects of blast injury on brain function and structure. We hypothesize that Operation Iraqi Freedom OIF soldiers injured by explosive blast will be distinguishable from those with post-traumatic stress disorder PTSD on measures of brain function and structure. Specifically, blast exposure will be associated with diminished P3a amplitudes to target stimuli during sustained attention and diminished lateralized frontal potentials during recognition of previously presented words. Individuals with PTSD will exhibit normal amplitudes of P3 and lateralized frontal brain potentials. Blast affected soldiers will also have compromised white matter integrity in supracallosal, inferior frontal, and superior frontal brain regions while PTSD will not be associated with these structural abnormalities. Finally, functional brain anomalies e.g., P3a, and frontal white matter fractional anisotropy will be associated with the adaptive functioning of soldiers. 