A reappraisal of scopolamine effects on inhibition.
A series of related experiments was conducted to examine the effects of scopolamine on discrimination performance in the presence or absence of a stimulus signalling non-reinforcement. In Experiment 1, rats trained to respond on 1 of two levers in the presence of a 1000-Hz tone and on the other lever in the presence of a 3000-Hz tone were not reinforced when white noise was added to 1 of the tones. Pairing white noise with the other tone during an extinction session demonstrated that the white noise had become a conditioned inhibitory stimulus. In Experiment 2, scopolamine decreased responding and discrimination accuracy on the excitatory (reinforced) trials, and increased responding on the inhibitory (non-reinforced) trials. The magnitude of the drug's effect was similar on excitatory and inhibitory trials. Using combination of visual and auditory discriminative stimuli, Experiment 3 confirmed the results of Experiment 2. These experiments show that scopolamine disrupts animals' ability to discriminate, and that scopolamine-induced increases in non-rewarded responses cannot be attributed solely to a disinhibitory effect of the drug as Carlton (1969) and others have claimed.
D000818:Animals; D001307:Auditory Perception / Q000187:drug effects; D003214:Conditioning, Classical / Q000187:drug effects*; D004192:Discrimination, Psychological / Q000187:drug effects; D007266:Inhibition, Psychological; D008297:Male; D051381:Rats; D012601:Scopolamine / Q000494:pharmacology*; D014796:Visual Perception / Q000187:drug effects
D012601:Scopolamine