A circuit mechanism for differentiating positive and negative associations
Nature. 2015-04-01; 520(7549): 675-678
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The ability to differentiate stimuli predicting positive or negative outcomes is
critical for survival, and perturbations of emotional processing underlie many
psychiatric disease states. Synaptic plasticity in the basolateral amygdala
complex (BLA) mediates the acquisition of associative memories, both positive and
negative. Different populations of BLA neurons may encode fearful or rewarding
associations, but the identifying features of these populations and the synaptic
mechanisms of differentiating positive and negative emotional valence have
remained unknown. Here we show that BLA neurons projecting to the nucleus
accumbens (NAc projectors) or the centromedial amygdala (CeM projectors) undergo
opposing synaptic changes following fear or reward conditioning. We find that
photostimulation of NAc projectors supports positive reinforcement while
photostimulation of CeM projectors mediates negative reinforcement.
Photoinhibition of CeM projectors impairs fear conditioning and enhances reward
conditioning. We characterize these functionally distinct neuronal populations by
comparing their electrophysiological, morphological and genetic features.
Overall, we provide a mechanistic explanation for the representation of positive
and negative associations within the amygdala.