Nucleus Accumbens Cell Type- and Input-Specific Suppression of Unproductive Reward Seeking.

The nucleus accumbens (NAc) contributes to behavioral inhibition and compulsions, but circuit mechanisms are unclear. Recent evidence suggests that amygdala and thalamic inputs exert opposing control over behavior, much like direct and indirect pathway output neurons. Accordingly, opponent processes between these NAc inputs or cell types may underlie efficient reward seeking. We assess the contributions of these circuit elements to mouse operant behavior during recurring conditions when reward is and is not available. Although direct pathway stimulation is rewarding and indirect pathway stimulation aversive, the activity of both cell types is elevated during periods of behavioral suppression, and the inhibition of either cell-type selectively increases unproductive reward seeking. Amygdala and thalamic inputs are also necessary for behavioral suppression, even though they both support self-stimulation and innervate different NAc subregions. These data suggest that efficient reward seeking relies on complementary activity across NAc cell types and inputs rather than opponent processes between them.

Coordinated Reductions in Excitatory Input to the Nucleus Accumbens Underlie Food Consumption.

Reward-seeking behavior is regulated by a diverse collection of inputs to the nucleus accumbens (NAc). The information encoded in each excitatory afferent to the NAc is unknown, in part because it is unclear when these pathways are active in relation to behavior. Here we compare the activity profiles of amygdala, hippocampal, and thalamic inputs to the NAc shell in mice performing a cued reward-seeking task using GCaMP-based fiber photometry. We find that the rostral and caudal ends of the NAc shell are innervated by distinct but intermingled populations of forebrain neurons that exhibit divergent feeding-related activity. In the rostral NAc shell, a coordinated network-wide reduction in excitatory drive correlates with feeding, and reduced input from individual pathways is sufficient to promote it. Overall, the data suggest that pathway-specific input activity at a population level may vary more across the NAc than between pathways.