Conditioning-specific modification of the rabbit's unconditioned nictitating membrane response.
Robust classical conditioning modifies responding to the unconditioned stimulus (US) in the absence of the conditioned stimulus (CS), a phenomenon the researchers called conditioning-specific reflex modification. Unconditioned responses (URs) to periorbital stimulation varying in intensity and duration were assessed before and after 1, 3, or 6 days of paired, explicitly unpaired, or no presentations of tone and electrical stimulation. After 3 days of pairings, conditioned responding (CRs) reached 94%, and there was an increase in latency to the peak of URs. The peak latency increase was replicated in a second experiment where rabbits reached asymptotic conditioning during 6 days of pairings. There was also a conditioning-specific increase in the amplitude of URs. There were no UR changes as a function of low level of CRs following 1 day of pairings. Data suggest that there are learning-specific changes in pathways mediating the US/UR, as well as in those mediating the CS/CR.
Schreurs
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Laboratory of Adaptive Systems, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892, USA.
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Hirashima
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Alkon
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D000818:Animals; D001245:Association Learning; D001288:Attention; D003214:Conditioning, Classical; D003215:Conditioning, Eyelid; D008297:Male; D011939:Mental Recall; D011817:Rabbits; D011930:Reaction Time