Temporal dynamics of nucleus accumbens neurons in male mice during reward seeking.

The nucleus accumbens (NAc) regulates reward-motivated behavior, but the temporal dynamics of NAc neurons that enable "free-willed" animals to obtain rewards remain elusive. Here, we recorded Ca²⁺ activity from individual NAc neurons when mice performed self-paced lever-presses for sucrose. NAc neurons exhibited three temporally-sequenced clusters, defined by times at which they exhibited increased Ca²⁺ activity: approximately 0, −2.5 or −5 sec relative to the lever-pressing. Dopamine D1 receptor (D1)-expressing neurons and D2-neurons formed the majority of the −5-sec versus −2.5-sec clusters, respectively, while both neuronal subtypes were represented in the 0-sec cluster. We found that pre-press activity patterns of D1- or D2-neurons could predict subsequent lever-presses. Inhibiting D1-neurons at −5 sec or D2-neurons at −2.5 sec, but not at other timepoints, reduced sucrose-motivated lever-pressing. We propose that the time-specific activity of D1- and D2-neurons mediate key temporal features of the NAc through which reward motivation initiates reward-seeking behavior. Volitional reward taking emerges through a sequence of preluding events. Yet, the underlying neural mechanism is not fully understood. Here authors show a series of temporal dynamics of nucleus accumbens neurons that may substantiate such preluding events to commit "free-willed" animals to reward taking. [ABSTRACT FROM AUTHOR]