Facilitatory effects of thalamic reticular nucleus lesions on two-way active avoidance in rats

Two experiments were performed in order to study the effects of lesions of the rostral thalamic reticular nucleus (Rt) on two-way active avoidance. Male Wistar rats were subjected to either a bilateral electrolytical lesion of the rostral Rt or to control procedures. After recovery, all rats were trained in either a distributed (five training sessions, ten trials each; experiment I) or a massed (a single 30-trials session; experiment II) two-way, active-avoidance task. The level of long-term retention of the task was assessed 10 days later. Lesioned rats showed an overall higher performance than control rats both in experiment I (with lesions affecting the rostral Rt and small portions of some adjacent nuclei) and in experiment II (with lesions almost restricted to the rostral Rt). In contrast, detrimental effects on other tasks have been reported in the literature. Although it cannot be ruled out that those differences might be due to methodological factors, they also might be indicative of an action of rostral Rt lesions on certain mechanisms (either indirectly or directly related to information processing) that could be differentially required depending on the kind of learning task. The latter possibility is discussed in terms of the role played by this nucleus as a modulator of thalamocortical transmission, attentional mechanisms and cortical arousal.