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Unread December 7th, 2009, 09:29 PM
James Brody James Brody is offline
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Arrow Trauma x Genes


Why We Don't All React to Trauma the Same Way: The answer might include genetic influences and an adrenergic-amygdala-insula connection.
Individuals have varying abilities to recall significant, or stressful, events.

Researchers have found that a deletion variant of the gene encoding for the {alpha}2b-adrenoreceptor (ADRA2B) enhances emotional memory in healthy controls and in individuals who had traumatic experiences during the Rwandan civil war.

The same study group has now examined the neuroanatomical localization for enhanced emotional memory.
The investigators used functional MRI to examine amygdala activity in 57 subjects as they looked at pictures with neutral or emotional content (mean age, 24; 16 men; 30 participants heterozygous or homozygous for the ADRA2B deletion variant).

All participants showed higher amygdala activity while looking at emotional versus neutral pictures, but activation, especially in the right amygdala, was even greater in carriers of the ADRA2B deletion variant.
When subjects' emotional subsequent memory was tested (i.e., examining brain activity during successful encoding of emotional memory), stronger activation was seen in the left insula of deletion carriers than of noncarriers. Analyses found greater connectivity between the right amygdala and left insula associated with negative pictures in deletion carriers.

Comment: A biological predisposition can have effects on symptoms, including intrusive memories of traumatic events. The {alpha}2b-adrenoreceptor is an autoreceptor that inhibits norepinephrine release. The authors hypothesize that the deletion variant acts as a loss-of-function polymorphism, resulting in increased norepinephrine activity. Enhanced amygdala activation and amygdala-insula interactions have been seen in patients with post-traumatic stress disorder, and insula activity may be related to PTSD flashbacks. Prazosin, an alpha-1 adrenergic antagonist, has been used for PTSD-associated nightmares, and the current study's finding is consistent with this application.

-- Jonathan Silver, MD

Published in Journal Watch Psychiatry December 7, 2009

Citation(s): Rasch B et al. A genetic variation of the noradrenergic system is related to differential amygdala activation during encoding of emotional memories. Proc Natl Acad Sci U S A 2009 Nov 10; 106:19191. (Subscription may be required) (Free)
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