Reversal learning protocols in the training of rats in the midsession reversal task

• Grant number: 25/10272-5
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: September 01, 2025
• End date: August 31, 2026
• Field of knowledge: Humanities - Psychology - Experimental Psychology
• Principal Investigator: Marcelo Bussotti Reyes
• Grantee: Fillipi da Rosa Ferreira
• Host Institution: Centro de Matemática, Computação e Cognição (CMCC). Universidade Federal do ABC (UFABC). Ministério da Educação (Brasil). Santo André , SP, Brazil
• Associated research grant: 22/16315-0 - The serial organization of behavior: studies with the mid-session reversal task, AP.R

Abstract

Human life is permeated by dilemmas involving the decision to remain in one action or switch to another. However, the processes that regulate how and why we make these switches are not yet fully understood. An experimental paradigm in animals has provided important clues: midsession reversal learning. In this paradigm, two distinct stimuli (S1 and S2) are presented; the choice of S1 is reinforced in the first half of the session, while the choice of S2 is reinforced in the second half-that is, the contingency between positive and negative stimuli reverses at the midpoint of the session. Previous research shows that pigeons adopt a suboptimal strategy: they initially prefer S1, but as the reversal approaches, they progressively choose S2, generating anticipation errors. After the reversal, they continue to choose S1 for a few trials, incurring perseveration errors, which decrease towards the end of the session. Studies with rats reveal different adaptations depending on the context: they can adopt either an optimal strategy, similar to that of humans, or a near-optimal strategy, similar to that observed in pigeons. Previous work by our group manipulated the interval between trials and showed that, even when performing near-optimally, rats resort to a temporal strategy. However, in these studies, S1 and S2 were always presented on the same side of the operant box, allowing the animals to use postural cues (e.g., staying closer to the chosen side) as mnemonic aids. The present study will investigate whether rats' performance deviates from optimal when this source of cues is eliminated. To this end, S1 and S2 will be presented randomly to the left or right of the operant box. Our hypothesis is that the absence of postural cues will increase both anticipation and perseveration errors, bringing the response pattern closer to that observed in rats trained in plus mazes.