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.
The proposed study offers a new approach of biological treatment for memory manipulations.
The findings will help elucidate the mechanism of PTSD-related memory impairment, and is
expected to contribute to the development of biological memory manipulations for treating
PTSD and other memory-related conditions.