CONDITIONING-SPECIFIC MODIFICATION OF THE RABBITS UNCONDITIONED NICTITATING-MEMBRANE RESPONSE

Robust classical conditioning modifies responding to the unconditioned stimulus (US) in the absence of the conditioned stimulus (CS), a phen omenon the researchers called conditioning-specific reflex modificatio n. 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 elect rical stimulation. After 3 days of pairings, conditioned responding (C Rs) reached 94%, and there was an increase in latency to the peak of U Rs. The peak latency increase was replicated in a second experiment wh ere rabbits reached asymptotic conditioning during 6 days of pairings. There was also a conditioning-specific increase in the amplitude of U Rs. There were no UR changes as a function of low level of CRs followi ng 1 day of pairings. Data suggest that there are learning-specific ch anges in pathways mediating the US/UR, as well as in those mediating t he CS/CR.