Mediodorsal thalamus is critical for updating during extra-dimensional shifts but not reversals in the attentional set-shifting task

Abstract

Cognitive flexibility, attributed to frontal cortex, is vital for navigating the complexities of everyday life. The mediodorsal thalamus (MD), interconnected to frontal cortex, may influence cognitive flexibility. Here rats performed an attentional set-shifting task measuring intra-dimensional and extra-dimensional shifts in sensory discriminations. MD lesion rats needed more trials to learn the rewarded sensory dimension. However, once the choice response strategy was established, learning further two-choice discriminations in the same sensory dimension, and reversals of the reward contingencies in the same dimension, were unimpaired. Critically though, MD lesion rats were impaired during the extra-dimensional shift, when they must rapidly update the optimal choice response strategy. Behavioral analyses showed MD lesion rats had significantly reduced on-the-fly correct second choice responses. Diminshed c-Fos expression in the prelimbic and orbitofrontal cortex was also documented. This evidence shows transfer of information via the MD is critical when monitoring and rapid updates in established choice response strategies are required.