Summary: Those with decreased activity in the hippocampus following a traumatic event are more likely to experience worse PTSD symptoms.
After a traumatic event, people with decreased activity in the hippocampus experience worse PTSD symptoms, according to new research published in Journal of Neuroscience.
The hippocampus does more than encode new memories — it also takes stock of spatial and emotional contexts and processes threat.
PTSD impacts all of these functions, generating symptoms like the overgeneralization of fear and recurrent traumatic memories. Yet the exact interplay between the hippocampal activity and PTSD was unclear.
Tanriverdi et al. measured PTSD symptoms and hippocampal activity in people who had visited the emergency room after a traumatic event like a car crash.
Participants answered a questionnaire about PTSD symptoms, then they viewed frightened and neutral faces while the researchers measured their brain activity with fMRI.
These results indicate certain individuals may be more susceptible to PTSD because of impaired activity in their hippocampus. Image is in the public domain
People with more severe PTSD symptoms had decreased activity in the hippocampus in response to the frightened faces. This relationship strengthened in people who startled more easily in a defensive learning task.
For these participants, their hippocampus may not be discriminating between safe and unsafe contexts.
These results indicate certain individuals may be more susceptible to PTSD because of impaired activity in their hippocampus.
Hippocampal Threat Reactivity Interacts with Physiological Arousal to Predict PTSD Symptoms
Hippocampal impairments are reliably associated with post-traumatic stress disorder (PTSD); however, little research has characterized how increased threat-sensitivity may interact with arousal responses to alter hippocampal reactivity, and further how these interactions relate to the sequelae of trauma-related symptoms.
In a sample of individuals recently exposed to trauma (N=116, 76 Female), we found that PTSD symptoms at 2-weeks were associated with decreased hippocampal responses to threat as assessed with functional magnetic resonance imaging (fMRI).
Further, the relationship between hippocampal threat sensitivity and PTSD symptomology only emerged in individuals who showed transient, high threat-related arousal, as assayed by an independently collected measure of Fear Potentiated Startle. Collectively, our finding suggests that development of PTSD is associated with threat-related decreases in hippocampal function, due to increases in fear-potentiated arousal.