Gulf War illness (GWI) is characterized symptomatically in veterans who served in the 1990-1991 Gulf War by a constellation of symptoms including headache, pain, fatigue, gastrointestinal problems and alterations in cognition. Diagnostic tests and effective treatments have not been identified. The proposed project leverages existing brain imaging data from a sample of 1990-91 Gulf War veterans and includes an in-depth, detailed analysis of the integrity of the corticostriatal circuit using high resolution diffusion imaging. While institutional human subjects approvals have been obtained during this period, there is no other progress to date under this award as the start of this project is pending initiation of the parent study which has been delayed due to DMDC regulation changes and delays in institutional contracting which are detailed in the annual reports for the parent grant. The revised timeline for the parent study has a data collection start date in the first quarter of 2016. Consistent with this delayed start, no funds have been used to date.