LESIONS OF THE FRONTAL-CORTEX, HIPPOCAMPUS, AND INTRALAMINAR THALAMICNUCLEI HAVE DISTINCT EFFECTS ON REMEMBERING IN RATS

Lesions of the intralaminar thalamic nuclei (ILn), the medial wall (MW area of prefrontal cortex, and the hippocampus were compared and foun d to have distinct effects on delayed matching-to-sample (DMS) and del ayed non-matching-to-sample(DNMS) tasks based on different types of st imulus cues. Hippocampal lesions impaired DNMS trained in a radial arm maze but had little effect on DMS trained with retractable levers or olfactory DNMS. MW lesions affected the DNMS task but had limited effe cts on olfactory DNMS and radial arm maze DNMS. ILn lesions resulted i n a more generalized pattern of impairment for radial maze tasks and t in previous studies) for the DMS and olfactory DNMS tasks. Only the hi ppocampal lesion was associated with a delay-dependent impairment. It is argued that nn lesions disrupt remembering through their effects on the recurrent, feedback pathways that link functionally related areas of the basal ganglia and cortex.