Hippocampus function predicts severity of post-traumatic stress disorder

Post-traumatic stress disorder (PTSD) is often accompanied by memory problems and abnor-mal brain structure, particularly within the hippocampus. We implemented a cross-species, hippocampal-dependent task—the virtual Morris Water task—to assess hippocampal func-tion in people with PTSD and age-matched controls during functional magnetic resonance imaging (fMRI). Performance on the task was equivalent between the groups. However, when correlating fMRI-derived hippocampal activity during this task with PTSD severity, we observe a 0.84 correlation, indicating that those with reduced hippocampal activity show more severe PTSD symptoms. This correlation is not explained by differences in task performance, IQ, duration since trauma, nor time with PTSD. Hence, PTSD severity is pre-dicted by functionally assessing the hippocampus using the virtual Morris water task, sug-gesting that this task may be used to identify those at risk for developing PTSD following a trauma. 23