Learning in rats with caudate-putamen lesions: unimpaired classical conditioning and beneficial effects of redundant stimulus cues on instrumental and spatial learning deficits.
The effects of caudate-putamen lesions in the rat on conditioning were investigated in three experiments. In Experiment 1, rats with lesions were impaired on a spatial task that required learning to make the correct position response, but no deficit was obtained when the alternatives were differentiated by salient visual cues. Performance remained good even when the visual cues were removed. A classical conditioned suppression paradigm was used in Experiment 2, and caudate-putamen lesions were found not to impair acquisition of suppression or overshadowing. In Experiment 3 we revealed poor instrumental learning in subjects with lesions as retarded acquisition of lever-press responding and depressed variable interval response rates. When a light stimulus was present together with reinforced responses, response rates were depressed in the control group (which suggested an overshadowing phenomenon) but were potentiated in the group with lesions. The results showed that caudate-putamen lesions did not produce a general deficit in association formation. There was disruption of learning about responses but not stimuli and, moreover, it was found that redundant stimulus cues aided response learning. It appears that for normal subjects, the salience or associability of the response cues may largely determine the influence of stimuli presented during instrumental conditioning.
Mitchell
J A
JA
University of Manchester, England.
Hall
G
G
D000818:Animals; D001245:Association Learning / Q000502:physiology; D001288:Attention / Q000502:physiology*; D002421:Caudate Nucleus / Q000502:physiology*; D003214:Conditioning, Classical / Q000502:physiology*; D003216:Conditioning, Operant / Q000502:physiology*; D003463:Cues; D004193:Discrimination Learning / Q000502:physiology; D008297:Male; D009042:Motivation / Q000502:physiology; D009949:Orientation / Q000502:physiology; D011699:Putamen / Q000502:physiology*; D051381:Rats; D011919:Rats, Inbred Strains; D013028:Space Perception / Q000502:physiology*