The rat's not for turning: Dissociating the psychological components of cognitive inflexibility

Abstract

Executive function is commonly assessed by assays of cognitive flexibility such as reversal learning and attentional set-shifting. Disrupted performance in these assays, apparent in many neuropsychiatric disorders, is frequently interpreted as inability to overcome prior associations with reward. However, non-rewarded or irrelevant associations may be of considerable importance in both discrimination learning and cognitive flexibility. Non-rewarded associations can have greater influence on choice behaviour than rewarded associations in discrimination learning. Pathology-related deficits in cognitive flexibility can produce selective disruptions to both the processing of irrelevant associations and associations with reward. Genetic and pharmacological animal models demonstrate that modulation of reversal learning may result from alterations in either rewarded or non-rewarded associations. Successful performance in assays of cognitive flexibility can therefore depend on a combination of rewarded, non-rewarded, and irrelevant associations derived from previous learning, accounting for some inconsistencies observed in the literature. Taking this combination into account may increase the validity of animal models and may also reveal pathology-specific differences in problem solving and executive function.

Keywords: Animal models; Attentional set shifting; Cognitive flexibility; Discrimination learning; Reversal learning.

Fig. 1

Performance of Lister Hooded rats on a touchscreen reversal learning task with interleaved CS+ vs. CS− presentations (visual discrimination, VD) and probe trials investigating perseverance and learned non-reward. Retention (Ret.) represents performance on the last 100 trials preceding reversal. ‘Early’ represents the first 100 trials after reversal, ‘Random’ represents 100 trials when performance on the VD trials have reached 50%, and ‘Late’ represents 100 trials when the rats have reached 80% accuracy on the VD trials. (a) Reversal-learning performance in the probe task does not differ from control rats tested on the VD trials only (test group: F_1,10 = .046, p = .834, group × group p = F_9,90 = .714, p = .695). (b) Accuracy on probe trials, i.e. choosing CS50/50 over CS− and choosing CS+ over CS50/50, is significantly above chance (50%) during retention (one-sample t-test, t₆ = 2.703, p = .035) and late reversal phases (t₆ = 3.532, p = .0123), whereas performance drops below chance during early reversal (t₆ = 2.677, p = .0367). (c) Number of errors on perseverance and learned non-reward probe trials does not differ (paired t-test, t₆ = 0.242, p = .817), indicating that the task equally assesses previous positive and negative associations in reversal learning.