Where do a person’s bad memories go?
Investigators from Yale and Mount Sinai schools of medicine studied the neural activity of 28 people diagnosed with post-traumatic stress disorder (PTSD). They found that autobiographical memories for sad and neutral memories are processed differently in the brain than for traumatic memories.
The findings, published in Nature Neuroscience, suggest the processing of traumatic memories is possibly the result of a PTSD patient developing a highly detailed and very personal memory of the event, making that representation unique to that person.
Another possibility is that traumatic memory reactivation is not experienced as memory per se but is rather disconnected from time and space and from current surroundings, and thus experienced as an intrinsic mental event.
A third possibility is that patients attempted to block or suppress the reactivation of the traumatic content, and by doing so exhibited brain activity that was incongruent with other memories they may have had that are not traumatic.
“Our main finding, that hippocampal patterns of PTSD patients showed a differentiation in semantic representation by narrative type during memory reactivation, supports the idea of a profoundly separate cognitive experience in the reactivation of traumatic memories,” said Ilan Harpaz-Rotem, PhD, professor of psychiatry and of psychology at Yale School of Medicine and the paper’s co-senior author.
“This is consistent with the notion that traumatic memories are not experienced as memories per se,” said Harpaz-Rotem, who is also a member of Yale Center for Brian and Mind Health and the Wu Tsai Institute. “Rather, these are fragments of prior events, subjugating the present moment to evade the comfort of belonging to the past.”
He said the results are crucial to scientists’ understanding of the significant role of recalling these fragments of past trauma and processing them, to recreate a coherent narrative that can be reconsolidated and organized as critical components of PTSD treatment.
The 28 subjects underwent reactivation of autobiographical memory through script-driven imagery while undergoing functional magnetic resonance imaging (fMRI). The data was collected at Yale and was analyzed in collaboration with the Mount Sinai team.
Other authors affiliated with Yale School of Medicine are Or Duek, PhD; Charles Gordon, MA; John Krystal, MD; and Ifat Levy, PhD. Daniela Schiller, PhD, from Mount Sinai was co-senior author with Harpaz-Rotem.
Funding was provided by an Independent Investigator Grant from the Brain and Behavior Research Foundation (IHR), by the Clinical Neurosciences Division of the National Center for PTSD (IHR), and the Yale Center for Clinical Investigation (YCCI) supported by CTSA Grant from the National Center for Advancing Translational Science (NCATS), a component of the National Institutes of Health (NIH).