Disconnection of the entorhinal cortex and dorsomedial striatum impairs the sensitivity to instrumental contingency degradation.

The capacity to detect changes in the causal efficacy of actions is mediated by a number of brain areas, including the entorhinal cortex (EC) and the posterior part of the dorsomedial striatum (pDMS). In this study we examined whether interactions between the EC and pDMS are required to detect changes in the instrumental contingency. Rats that received EC-pDMS disconnection lesions, that is, unilateral cell body lesions of the EC and contralateral dopamine depletions of the pDMS, were trained to press two levers, with one delivering food pellets and the other a sucrose solution. Thereafter, we tested whether rats were sensitive (1) to a selective devaluation of the value of one of two outcomes using a specific satiety procedure, and (2) to a selective degradation of one of two contingencies controlling instrumental choice behavior. Our results reveal that rats with EC-pDMS disconnection lesions were sensitive to outcome devaluation. However, unlike rats with sham lesions or unilateral EC and pDMS lesions, rats with EC-pDMS disconnection lesions showed a reduced sensitivity to contingency degradation. These findings suggest that EC and pDMS may be part of a neural system that supports the detection of changes in the causal relationship between an action and its consequences.