A neuronal signature for monogamous reunion

Pair bond formation depends vitally on neuromodulatory signaling within the nucleus accumbens, but the neuronal dynamics underlying this behavior remain unclear. Using in vivo Ca 2+ imaging in monogamous prairie voles, we found that pair bonding does not elicit differences in overall nucleus accumbens Ca 2+ activity. Instead, we identified distinct neuronal ensembles in this region recruited during approach to either a partner or novel vole. The partner-approach neuronal ensemble increased in size following bond formation and differences in the size of approach ensembles for partner and novel voles predicts bond strength. In contrast, neurons comprising departure ensembles do not change over time and are not correlated with bond strength indicating that ensemble plasticity is specific to partner approach. Further, the neurons comprising partner and novel approach ensembles are non-overlapping while departure ensembles are more overlapping than chance, which may reflect another key feature of approach ensembles. We posit that the features of the partner approach ensemble and its expansion upon bond formation make it a potential key substrate underlying bond formation and maturation. Highlights We performed in vivo Ca 2+ in the nucleus accumbens of pair bonded prairie voles Overall nucleus accumbens activity did not differ during partner versus stranger interaction Distinct approach neurons exist for the partner and for the stranger Partner-approach ensemble increases as partner preference emerges We identify a putative neuronal substrate underlying bond formation and maturation