Aim 7.1: To determine the effect of ibogaine treatment on whole brain connectivity as measured by changes in functional connectivity patterns of brain networks from baseline to immediate post treatment in an observational study of individuals with history of TBI. Aim 7.2: To determine if resting state fMRI changes correlate with cerebral perfusion (ASL) changes between baseline and immediate post treatment, and baseline and one-month post-treatment in an observational study of individuals with a history of TBI. Aim 7.3: To determine whether Ibogaine treatment results in decreased within network connectivity of the default mode network from baseline to immediate post treatment in an observational study of individuals with a history of TBI. Aim 7.4: To determine whether Ibogaine treatment results in increased global interconnectivity between previously defined brain networks from baseline to immediate post treatment in an observational study of individuals with a history of TBI. Aim 7.5: To determine whether Ibogaine treatment results in decreased within network connectivity between previously defined brain networks from baseline to immediate post treatment in an observational study of individuals with a history of TBI. Aim 7.6: To determine whether observed changes in between and within network connectivity correlate with observed changes in cognitive function and clinical symptoms from baseline to immediate post treatment in an observational study of individuals with a history of TBI. Aim 7.7. To test the following hypothesis: Using the AFQ method, at baseline, our participants’ FA will be negatively correlated with the number of blast exposures and with time elapsed since the most severe blast exposure in the following white matter tracts: 1) cingulum bundle, 2) uncinate fasciculus, 3) superior longitudinal fasciculus, 4) inferior longitudinal fasciculus, and the 5) anterior thalamic radiation. Lower FA in the tracts listed above will also be correlated with greater PTSD symptoms and worse neurocognitive performance. Note: for hypothesis justifications see https://onlinelibrary.wiley.com/doi/epdf/10.1002/hbm.23365 and https://doi.org/10.1016/j.ynirp.2021.100047 (note: this hypothesis was registered after data collection but prior to the specific analysis described here). Aim 7.8. To test the following hypothesis: Ibogaine therapy will be associated with increased FA at the 1-month time point as compared to baseline in 1) cingulum bundle, 2) uncinate fasciculus, 3) superior longitudinal fasciculus, 4) inferior longitudinal fasciculus, and the 5) anterior thalamic radiation. Increases in FA in those tracts will be correlated with reduced PTSD symptoms and improved neurocognitive performance. Note: for hypothesis justifications see https://onlinelibrary.wiley.com/doi/epdf/10.1002/hbm.23365 and https://doi.org/10.1016/j.ynirp.2021.100047 (note: this hypothesis was registered after data collection but prior to the specific analysis described here). Aim 7.9. To test the following hypothesis: Brain age at a point in time will be negatively correlated with FA at a point in time in the white matter tracts listed in Aim 7.7 above. (note: this hypothesis was registered after data collection but prior to the specific analysis described here). Aim 7.10. To test the following hypothesis: Reductions in brain age from baseline to immediate post and to one month will be negatively correlated with increases in FA in the white matter tracts listed in Aim 7.7 above. (note: this hypothesis was registered after data collection but prior to the specific analysis described here). Aim 7.11. To test the following hypothesis: Reductions in PTSD symptoms and improvements in cognitive performance will be correlated with reductions in brain age, and this effect will be mediated by improvements in FA in the tracts listed in Aim 7.7 above. (note: this hypothesis was registered after data collection but prior to the specific analysis described here). Aim 7.12. To test the following hypothesis: Using the AFQ method, at baseline, our participants’ FA will be negatively correlated with the number of blast exposures and with the time elapsed since the most severe blast exposure in the following white matter tracts: 1) the suprachiasmatic nucleus, 2) paraventricular nucleus, 3) optic tract (optic chiasm + left and right lateral geniculate) 4) optic nerve, and the 5) retinohypothalamic tract. Lower FA in the tracts listed above will also be correlated with symptoms of poor sleep and worse neurocognitive performance. Note: for hypothesis justifications see https://www.sciencedirect.com/science/article/pii/B9780128093245023919 and https://www.sciencedirect.com/science/article/abs/pii/B9780444529039000145 and https://www.sciencedirect.com/science/article/abs/pii/S0010945219300309?via%3Dihub and https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3482689/ and https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0046204 and https://www.mdpi.com/2079-7737/11/7/1031/pdf (note: this hypothesis was registered after data collection but prior to the specific analysis described here). Aim 7.13. To test the following hypothesis: Ibogaine therapy will be associated with increased FA at the 1-month time point as compared to baseline in 1) the suprachiasmatic nucleus, 2) paraventricular nucleus, 3) optic tract (optic chiasm + left and right lateral geniculate) 4) optic nerve, and the 5) retinohypothalamic tract. Increases in FA in those tracts will be correlated with improved sleep. Note: for hypothesis justifications see https://www.sciencedirect.com/science/article/pii/B9780128093245023919 and https://www.sciencedirect.com/science/article/abs/pii/B9780444529039000145 and https://www.sciencedirect.com/science/article/abs/pii/S0010945219300309?via%3Dihub (note: this hypothesis was registered after data collection but prior to the specific analysis described here).