Intra- And Extra-Dimensional Learning in the Common Marmoset

Abstract

Cognitive flexibility is the brain’s ability to suppress the current strategy in favour of a better alternative when the context changes. Impaired cognitive flexibility is a transdiagnostic deficit in several neuropsychiatric disorders. How the primate brain supports this process is not well understood. We trained 4 marmosets on a novel intra- and extra-dimensional shifting (IEDS) task involving 2 dimensions: shape and colour. They were pre-trained on each of the 6 features (3 shapes and 3 colours) separately, which were then combined into compound stimuli. Marmosets were required to select the compound stimulus with the target feature (e.g. red). After reaching criterion (8/10 correct), the target feature shifted within or across dimensions. Next, we implemented a feature reinforcement learning model, and found that the estimated learning rate, choice determinism and attentional parameters for marmosets fell within the range typically observed in healthy humans, underscoring translational value.