Enhanced Hippocampal Neuroplasticity for Surfacing of Inaccessible Traumatic Memories in Veterans With PTSD

Our memory constructs a sense of coherence and defines the way we perceive the world. Effective encoding of memories in an adequate context, and their deliberate retrieval at a later time, are crucial for maintaining biographic continuity, and are both heavily dependent on hippocampal function.

Post-traumatic stress disorder (PTSD) can be considered a prototype disorder in which a stressogenic event leads to hippocampal malfunction and mal-encoding of a traumatic memory. Persistent hippocampal dysfunction contributes to the unremitting nature of PTSD years after the acute event. The upshot is not only amnesia, but also difficulty in memory integration in the context of time and location, and the feeling that the traumatic event is present all the time and everywhere. Improved hippocampal function may contribute to better access to memories of a traumatic event and to memory contextualization and neutralization. Memory processing is essential for PTSD recovery.

Hyperbaric oxygen therapy (HBOT) includes the inhalation of 100% oxygen at pressures exceeding one atmosphere absolute. HBOT has been applied worldwide, mostly for chronic non-healing wounds. Our team demonstrated that HBOT induced hippocampal neuroplasticity in veterans with long-standing treatment-resistant PTSD; this led to enhanced memory recovery and significant improvement in PTSD symptoms. The investigators also demonstrated effects of HBOT on memory recovery among women with fibromyalgia due to childhood sexual abuse.

Both physical activity, such as aerobic exercise, and cognitive training were shown to support neurogenesis in the hippocampus. Therefore, the current study aims to evaluate whether hippocampal training, induced by physical and cognitive training, will augment the hippocampal neuroplasticity effect of HBOT and further enhance recovery of inaccessible memories in veterans with PTSD.

The protocol will include forty male veterans aged 25 to 60 years, with combat-associated PTSD and peritraumatic amnesia, who will receive either HBOT alone or HBOT and hippocampal training. The HBOT protocol will consist of 60 daily sessions, 90-minutes each, five days a week. Hippocampal training will combine physical and cognitive training 3 times per week, prior to HBOT sessions. Detailed psychological evaluation, anatomic and functional MRI, electroencephalogram and autonomic nervous system data will be obtained at baseline, and during and after treatment.