Environmental complexity modulates information processing and the balance between decision-making systems

Decision-making relies on dynamic interplay between multiple neural circuits and decision-making systems integrating past experiences, current goals, and environmental demands. Past studies of rodent decision-making have largely occurred in simple environments and on isolated brain areas. This leaves unclear the impact of environmental complexity on the interaction between multiple brain areas to set adaptive strategies. To fill this gap, we either recorded neural activity across the key regions of hippocampus (HC), dorsolateral striatum (DLS), and medial prefrontal cortex (mPFC) or chemogenetically inactivated mPFC in a separate cohort while rats foraged for food under changing rules in differently complex environment. Environmental complexity increased behavioral variability, lengthened HC nonlocal sequences, and introduced intermediary subgoals. We found contrasting representations between DLS and HC, supporting a competition between decision systems. mPFC activity was indicative of setting this balance, in particular predicting nonlocal HC coding. Inactivating mPFC impaired short-term behavioral adaptation and produced long-term deficits balancing decision systems. Our findings reveal the dynamic nature of decision-making systems and how environmental complexity modulates their engagement with implications for behavior within naturalistic environments.