Neural circuits do not operate in the same state throughout the day. Neuromodulator release, baseline neural activity, behavioral drive, and responses to salient events can all vary with circadian phase.

We use long-term fiber photometry and behavioral monitoring to measure neural signals repeatedly across days and weeks. In the nucleus accumbens, for example, we found that spontaneous dopamine release, reward-evoked dopamine signals, and reward-related behavior peak at different circadian phases. The relationships among these signals also change across the day.

More broadly, we ask how circadian signals and local molecular clocks shape the operating state of neural circuits and, in turn, alter the relationship between neural activity and behavior.