MAPPING THE BRAIN: UNVEILING THE NEURAL MECHANISMS OF SIGN-TRACKING AND GOAL-TRACKING BEHAVIOUR

Evaluative learning entails the association of sensory stimuli, used as conditioned stimuli (CS), with an intrinsically rewarding stimulus (US). Notably, significant inter-individual variability exists regarding how learning is manifested in animals (and humans). Some individuals display signtracking behaviour, with CS gaining incentive salience and driving automatic attention/approach; for others, CS are learned as informative reward predictors, known as goal-tracking. The current study aims at investigating major neurocognitive mechanisms underlying evaluative learning by assessing varying behavioural phenotypes, and related brain activity, in the rat model. Seventy-eight SD rats, enrolled in a Pavlovian Conditioning Approach paradigm, experienced repeated pairings (30 trials/session) of a retractable lever and a tone (CS) with sucrose pellets (US). The protocol comprised 8 sessions, after which rats were perfused to perform brain slicing and processing by immunohistochemistry for the brain expression of the immediate early gene c-Fos, and by immunofluorescence for the labelling of excitatory and inhibitory neurons, using CamKII and PV, respectively. Following a standardized approach, we quantified any bias in the speed/frequency of rat contacts with the CS or the US at session #8 to classify animals as pure sign- or goal-trackers. Behavioral results showed clearly distinct learning manifestations: along sessions, during CS presentation, sign-trackers developed a tendency to quickly and repeatedly approach the cue stimuli, while goal trackers showed increased focusing onto the reward location. Moreover, pure phenotypes showed activation differences in specific brain regions, including areas within the dopaminergic system, frontal areas and sensory cortices, indicating potentially distinct pathways underlying the two opposing behaviors.