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Dopamine Subcircuits in Reinforcement Learning, Decision-Making, and Habit Formation
Dopamine signaling in the dorsomedial striatum promotes compulsive behavior (Seiler et al., Current Biology, 2022).
Here we observed activity in SNc dopamine neurons axons in the dorsomedial striatum (DMS) using fiber photometry. The signals were recorded while mice made nosepoke responses in a behavioral chamber to receive sugar pellets. The signals recorded from DMS dopamine axons predicted the number of shocks mice would tolerate when presented with a risk of footshock punishment for nosepoking. These data demonstrate that individual differences in compulsive reward-seeking can be explained, at least in part, by differences in dopamine circuit function between individual subjects.
Striatonigrostriatal circuit architecture for disinhibition of dopamine signaling (Ambrosi and Lerner, Cell Reports, 2022).
Here, we investigated how parallel basal ganglia subcircuits may interact through the dopamine system. We used electrophysiology, in concert with transsynaptic and intersectional genetic tools, to study these striatonigrostriatal circuits, one of which (the “ascending spiral”) has been long hypothesized to underlie habit formation. We found strong evidence that synaptic connectivity in closed-loop striatonigrostriatal circuits can regulate dopamine neuron firing. Connectivity in the ascending spiral is present, but the circuit cannot support straightforward disinhibition of DLS dopamine signaling. Finally, we discovered a previously uncharacterized “descending spiral” whose function remains mysterious, but of interest for future studies.
Region-specific Nucleus Accumbens Dopamine Signals Encode Distinct Aspects of Avoidance Learning (Lopez et al., bioRxiv, 2024).
In this study, we examined what computations dopamine signals perform to support avoidance learning. To understand how heterogeneous dopamine responses to aversive stimuli contribute to avoidance learning, we used fiber photometry to record NAc core (Core) and NAc ventromedial shell (vmShell) dopamine during a task in which mice could avoid a footshock punishment by moving to the opposite side of a 2-chamber apparatus during a five-second warning cue. Mice could either completely avoid a shock by crossing within 5s (blue) or escape shocks that started after 5s (orange). On both avoid and escape trails across days of training, NAc Core and vmShell dopamine signals are very different, but both evolve substantially with learning. Based on this data, we suggest that NAc vmShell dopamine guides initial cue-shock associations while NAc Core dopamine encodes prediction errors that guide the consolidation of avoidance learning.
