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Research highlights significance of resting metabolism in fear circuitry of PTSD

Recent findings indicated resting metabolism in fear circuitry was associated with functioning, PTSD symptoms and extinction recall activations.

“Exposure-based therapy, an effective treatment for [PTSD], relies on extinction learning principles. In PTSD patients, dysfunctional patterns in the neural circuitry underlying fear extinction have been observed using resting-state or functional activation measures,” Marie-France Marin, PhD, of Massachusetts General Hospital, Boston, and colleagues wrote. “It remains undetermined whether resting activity predicts activations during extinction recall or PTSD symptom severity. Moreover, it remains unclear whether trauma exposure per se affects resting activity in this circuitry.”

To assess relationships between resting metabolism, clinical systems and activations during extinction recall in PTSD, researchers evaluated 24 individuals with PTSD, 20 individuals exposed to trauma with no PTSD, and 21 healthy comparison subjects unexposed to trauma. Resting positron emission tomography scans were conducted 4 days before a functional MRI fear conditioning and extinction paradigm.

Amygdala resting metabolism was negatively associated with clinical functioning in trauma-exposed individuals without PTSD.

Hippocampal resting metabolism was negatively associated with clinical functioning in individuals with PTSD.

Dorsal anterior cingulate cortex resting metabolism positively correlated with PTSD symptom severity, and predicted increased activations in the dorsal anterior cingulate cortex, but decreased activations in the hippocampal and ventromedial prefrontal cortex during extinction recall.

Trauma-exposed individuals without PTSD had lower amygdala resting metabolism compared with individuals with PTSD and controls, and exhibited lower hippocampus resting metabolism compared with controls.

“Our findings support the importance of examining resting metabolism in the fear extinction network. In fact, our results highlight the fact that the neural effects of trauma exposure and PTSD diagnosis can be observed at rest, without probing the network with fear-related stimuli. Our findings also highlight the utility of examining resting metabolism in the nodes of the fear extinction network to predict activations in the network during extinction recall,” the researchers wrote. “Given the established relationship between extinction and exposure-based therapy and the fact that individuals with PTSD show impairments in extinction recall at the psychophysiological and neural levels, it is crucial to identify predictors of such dysfunctional patterns to better inform treatment.” – by Amanda Oldt

Disclosure: The researchers report no relevant financial disclosures.