A genetic variation of the noradrenergic system is related to differential amygdala activation during encoding of emotional memories

Abstract

Emotionally arousing events are typically well remembered, but there is a large interindividual variability for this phenomenon. We have recently shown that a functional deletion variant of ADRA2B, the gene encoding the alpha2b-adrenergic receptor, is related to enhanced emotional memory in healthy humans and enhanced traumatic memory in war victims. Here, we investigated the neural mechanisms of this effect in healthy participants by using fMRI. Carriers of the ADRA2B deletion variant exhibited increased activation of the amygdala during encoding of photographs with negative emotional valence compared with noncarriers of the deletion. Additionally, functional connectivity between amygdala and insula was significantly stronger in deletion carriers. The present findings indicate that the ADRA2B deletion variant is related to increased responsivity and connectivity of brain regions implicated in emotional memory.

Fig. 1.

Genotype-independent amygdala activation during encoding of negative vs. neutral pictures. The t values from the one-sample t test (red-white) are overlaid on a T1 template and displayed at a threshold of P(FWE) < 0.05, FWE-corrected for the whole brain. The anatomical defined bilateral amygdala (Talairach atlas) is indicated in blue. Left corresponds to the left side of the brain.

Fig. 2.

Genotype-dependent brain activity in the amygdala. (A) Carriers of the ADRA2B deletion variant activated the right amygdala in response to negative vs. neutral images to a greater extent compared with noncarriers [P(SVC) < 0.05, displayed at an uncorrected threshold of P = 0.005]. The white circle indicates the activation in the right amygdala. (B) Parameter estimates at the peak voxel in the right amygdala for noncarriers and carriers of the deletion.

Fig. 3.

Genotype-dependent differences in connectivity between the right amygdala and the left insula. (A) In deletion carriers, amygdala and insula activity was positively coupled during encoding of negative pictures, whereas an inverse association was observed in noncarriers. The difference in connectivity estimates between the genotype groups was significant (P = 0.001, displayed at a threshold of P = 0.005). The white circle indicates the increase in connectivity in the left insula. (B) Parameter estimates for the genotype-specific difference in connectivity with the amygdala in the left insula.