A cortical circuit mechanism for coding and updating task structural knowledge in inference-based decision-making

Abstract

Making decisions based on knowledge about causal environmental structures is a hallmark of higher cognition in mammalian brains. Despite mounting work in psychological and cognitive sciences, how the brain implements knowledge-based decision-making at neuronal circuit level remains a terra incognita. Here we established an inference-based auditory categorization task, where mice performed within-session re-categorization of stimuli by inferring the changing task rules. Using a belief-state reinforcement learning (BS-RL) model, we quantified the hidden variable associated with task knowledge. Using simultaneous two-photon population imaging and projection-specific optogenetics, we found that a subpopulation of auditory cortex (ACx) neurons encoded the hidden task-rule variable, which depended on the feedback input from orbitofrontal cortex (OFC). Chemogenetic silencing of the OFC-ACx projection specifically disrupted re-categorization performance. Finally, imaging from OFC axons within ACx revealed task state-related value signals in line with the modeled updating mechanism. Our results provide a cortical circuit mechanism underlying inference-based decision-making.

Neural codes in early sensory areas maximize fitness

“…Crucially, our findings indicate that downstream circuits do not necessarily need to continuously compute reward distributions based on stimulus-outcome associations because this information can be efficiently embedded in the neural codes of early sensory systems. This notion is supported by a recent study showing that functional remapping of stimulus-reward contingencies in early sensory areas causally depends on top-down control signals from prefrontal structures (23,24,33). We argue that this gives the organism the advantage of rapidly transmitting behaviorally-relevant information encoded by early sensory systems to downstream circuits specialized in action, learning, or decision-making.…”