| Abstract: | Attempted to determine the degree to which lesions in the septum and anatomically related structures result in the presence and/or permanence of overresponding on a DRL 20-sec schedule. Male Long-Evans hooded rats were given 15 days of training to determine the presence or absence of overresponding. Ss that overresponded were divided into 2 groups, with one receiving 15 days of cued DRL training and the other receiving 15 days of regular DRL training. Overresponding occurred in 60 Ss following lesions in septum, hippocampus, medialis dorsalis, and ventral thalamus pars dorsalis. While in effect, cued DRL facilitated performance in 8 controls and in operated Ss but did not facilitate performance when removed in septals. Exposure to the cued DRL allowed hippocampals to reduce responding and increase the frequency of obtained reinforcements. Lesions in medialis dorsalis and ventral thalamus led to an overresponding that disappeared with prolonged regular DRL training. Cued DRL training actually functioned as a time-out from DRL training. Variations in the permanence of the overresponding symptom according to lesion locus preclude identification of the lesion-induced dysfunction based solely on the presence or absence of overresponding. (18 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved) |
