The touchscreen operant platform for assessing cognitive functions in a rat model of depression

摘要

In the present study we assessed alterations in cognitive functions in a chronic mild stress (CMS) rat model of depression. Cognitive functions were assessed in two different tasks applying the translational operant platform touchscreen technology; the visual discrimination/acquisition task was used to assess the ability to perceive and distinguish visual stimuli and to assess associative stimulus-reward learning. The visual discrimination/reversal learning task was used to assess functional brain plasticity or reprogramming of previously acquired stimulus reward associations. These tasks permit the dissociation of multiple cognitive domains. The CMS model is a validated depression model with the useful feature that rats upon stress exposure show a graduated, individual stress response allowing the segregation of rats into different phenotypes including stress-resilient and anhedonic-like subgroups. Anhedonic-like rats are less likely to acquire the pairwise discrimination task, and they have a slower acquisition rate than controls. In the reversal learning task, resilient rats performed significantly better than anhedonic-like rats over time and 50% passed criterion as opposed to 25% for controls and only 14% for anhedonic-like rats. This indicates that resilient rats have higher cognitive flexibility than anhedonic-like rats. Thus they perform better in learning a novel task, which at the same time potentially implies an increased ability to inhibit previously rewarded behavior. (C) 2016 Elsevier Inc. All rights reserved.