| Abstract: | Tested S. T. Mason's hypothesis (1980) that lesions of the dorsal noradrenergic bundle (DNB), which induce depletion of forebrain noradrenaline, alter performance of discrimination tasks because they retard habituation to naturally attractive, but instrumentally irrelevant, stimuli. Exp I used 100 male Wistar rats in groups with either vehicle or 6-hydroxydopamine injections into the DNB. Groups were assigned to 5 discrimination tasks in a cross-maze. Lesions of the DNB did not alter performance of any of the tasks. In Exp II, control and noradrenaline-depleted Ss were trained in a task of light–dark discrimination followed by shift to position discrimination in a Y-maze. At the onset of training, Ss of both groups reliably avoided the bright goal arm and responded to the dark arm, thus demonstrating predominant attention for the relevant brightness stimuli rather than the irrelevant position stimuli. DNB lesions impaired acquisition of brightness discrimination only when the positive stimulus was the illuminated goal arm, and they did not alter shift performance. These results do not support Mason's hypothesis; but on the other hand they do indicate that DNB lesions in the rat can impair habituation of light avoidance. (25 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved) |
