Understanding the neural circuits involved in the balance of learning between cues with different proximity to rewards.

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We have shown that the lateral hypothalamus differently regulates learning about cues depending on the relative temporal distance of the cues to rewarding outcomes (Sharpe et al., 2017, Current Biology; Sharpe et al., 2021, Nature Neuroscience). This opens up a new avenue for neuroscience research, which is to understand the dynamics of how the brain prioritises learning and behaviour towards information most relevant to desirable outcomes. To formally investigate this using computational modelling and optogenetics in rats, we adapted the “Daw two-step task”, which quantifies the ability of human subjects to use complex task structure to predict rewards (e.g., Daw et al., 2011, Neuron). This task enables us to measure the weights of distal and proximal cues on future decision making. In our task, rats first receive one of two distal cues followed by presentation of two levers. Rats press one of the levers and then receive one of two proximal cues. The distal cues inform the probabilistic state transitions from the lever choice to the proximal cues. In turn, the proximal cues inform the fluctuating reward probabilities. We found that rats are able to guide their choices by using the transitional structure of the task, including significant weightings on decision making by both the distal and proximal cues. We are now combining our task with optogenetic approaches to parse the contribution of lateral hypothalamus and orbitofrontal cortex in the balance of learning and behaviour between distal and proximal cues of rewards.