How does hunger and food reward control learning

Learning is essential to successfully adapt to changing environments. The process of learning uses experience to guide current and future behaviour to maximise beneficial outcomes and minimise adverse outcomes. This is classically observed in nature where animals utilise learned cues to guide behaviour. Anyone with pets or with a farming background will know that food is one of the strongest universal behavioural rewards (reinforcers), and that food deprivation or food tastiness motivates the appropriate behaviour by increasing the rewarding value of food (reinforcement). From cows following the tractor at feeding time to dogs trained to guide visually impaired people, food is the defining behavioural reward promoting these learned behaviours. Therefore, it is no surprise that hunger has provided one of the strongest evolutionary survival pressures to optimise behaviour. For example, hunger increases the motivation to learn and successfully save new information, such as the location and quality of different food sources, which can be recalled later when needed. Without an appropriate strategy based on experience-dependent learning, food-seeking behaviour could exhaust an animal’s limited energy reserves in environments with an unknown food supply. Indeed, food-seeking and intake is reduced in hungry mice when placed in unfamiliar territory, which slowly changes with habituation to the territory. This demonstrates that experience-dependent learning is required to optimise food seeking and intake. Yet, even with decades of behavioural neuroscience research and millennia of agricultural practices showing that hunger and food reward (reinforcement) enhances learning, it is astonishing that we still don’t know how brain circuits sensing hunger influence experience-dependent learning. Because hunger and feeding behaviour affect learning, we hypothesised that hunger-sensing neurons should regulate learning and reflect this through changes in neural activity. Indeed, a population of neurons in the arcuate nucleus of the hypothalamus, characterised by the expression of Agouti-Related Peptide (AgRP), are recognised as canonical hunger sensing neurons that increase food intake. Thus, AgRP neurons are prime candidates linking hunger with learning. What are the key research aims? 1. Decode simultaneous neural responses in hunger and reward pathways during learning. 2. Assess the co-reliance of hunger and reward pathways on learning. 3. Control behavioural performance by artificially replicating the activity of hunger pathways.