Amygdalo–striatal neurons have been implicated in the processing of appetitive and aversive valence. Adding to our understanding of this neural pathway’s heterogeneity, Tian, Song et al. found that mice in which the anterior commissure was transected, which lack interhemispheric projections from basolateral amygdala (BLA) to contralateral nucleus accumbens (NAc), show blunted aversion. Strikingly, contralateral and ipsilateral BLA–NAc neurons were found to be largely separate populations. In intact mice, contralateral BLA–NAc neurons tended to be activated by aversive stimuli and suppressed by reward, whereas ipsilateral BLA–NAc neurons were activated by reward and suppressed by aversive stimuli. Selective activation and inhibition of contralateral neurons promoted and suppressed aversion, respectively, whereas ipsilateral neuron activation promoted appetitive behaviors. The authors showed that ipsilateral BLA–NAc neurons primarily target and activate D1 medium spiny neurons (MSNs) and might mediate appetitive valence by promoting dopamine release in the NAc. By contrast, contralateral BLA–NAc neurons primarily target D2 MSNs and mediate negative valence. These results extend our understanding of amygdalo-accumbal projection neurons and aversive coding in the brain.

Original reference: Science 386, eadp7520 (2024)