Reduced posterior hippocampal volume in posttraumatic stress disorder

Objective: Hippocampal volume is reduced in posttraumatic stress disorder (PTSD). In the we sought to determine whether present study, volume loss is homogenously distributed or confined to a certain part of the structure. Method: Twenty-two adult outpatients with PTSD (11 after prolonged prepubertal trauma single adult trauma) and 22 matched and 11 after. healthy subjects were scanned at the National Institute of Mental Health using high-resolution 3T magnetic resonance imaging between September 2003 and August 2004. PTSD diagnosis was conferred using the Structured Clinical Interview for DSM-IV. Volumes of whole, anterior, and posterior hippocampus and subiculum were compared between groups. Results: Total hippocampal volume was lower in patients with PTSD (p = .02), with a significant diagnosis by hippocampal-subregion interaction (p = .02). Post hoc analysis revealed significantly smaller posterior hippocampi in PTSD (p = .006) with no difference in the volumes of anterior hippocampus or subiculum. No volume differences were found between PTSD participants with prolonged childhood abuse compared to single adult trauma exposure. Conclusions: The posterior hippocampus has been associated with storage, processing, and retrieval of spatiotemporal memories, central to the protective function of fear conditioning. Volume deficit in the posterior hippocampus may indicate malfunction in this faculty, leading to the exaggerated conditioned fear response observed in PTSD.