Delayed matching-to-sample trained with retractable levers is impaired by lesions of the intralaminar or ventromedial but not the laterodorsal thalamic nuclei

Abstract

Rats were trained to perform a delayed matching-to-sample (DMS) task with retractable levers and were then given one of four treatments: control surgery or lesions of the intralaminar (ILn), ventromedial (VMn), or laterodorsal (LDn) thalamic nuclei. The ILn and VMn lesions affected response accuracy in a delay-independent fashion and were associated with slower response times for both the sample and the choice responses of the DMS task. The LDn lesion had little effect on this task. The effects of ILn and VMn lesions on DMS speed and accuracy are consistent with the findings of other studies on the effects of lesioning this area of thalamus and with impairments observed for human Korsakoff syndrome patients. It is argued that the effects of ILn and VMn lesions on DMS may be related to the function of these nuclei in the recurrent feedback pathways that connect functionally related areas of the basal ganglia and frontal cortex.