Fletcher BR, Baxter MG, Rapp PR, Shapiro ML (2003) 192-IgG saporin lesions of the medial septum and vertical diagonal band impair cognitive flexibility. Neuroscience 2003 Abstracts 425.8. Society for Neuroscience, New Orleans, LA.
Summary: Learning and memory remain largely intact following selective basal forebrain cholinergic lesions. By comparison, single unit recording studies have documented reliable effects of such lesions, including abnormally rigid hippocampal place fields when animals are confronted with changes in the configuration of the testing environment. The present experiment tested the prediction that cholinergic lesions of the basal forebrain would impair performance of tasks requiring cognitive flexibility. Rats received 192-IgG saporin or control vehicle injections into the medial septal nucleus and vertical diagonal band, and were tested on cued and spatial delayed match-to-place tasks in a radial arm water maze. Test sessions consisted of four sample trials in which animals searched for a cued or hidden escape platform located in a fixed position at the end of one arm (60 sec cutoff, inter-trial interval = 15 sec). A memory delay was imposed by returning rats to the home cage for a variable delay (15 sec. – 6 hrs), followed by two test trials. The lesion and control groups learned at similar rates in both versions of the task, and performed comparably on the critical test trials, independent of the length of the retention interval. However, lesioned rats were impaired during the transition from the cued to spatial variants of testing. Specifically, the lesion group made significantly more errors on an early sample trial in the spatial task, returning to the location that was previously correct during cued training. Pending histological confirmation of the extent and selectivity of the experimental lesions, this pattern of results suggests that damage to the basal forebrain cholinergic system spares spatial learning but impairs cognitive flexibility when task contingencies are changed.
Related Products: 192-IgG-SAP (Cat. #IT-01)