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Conditioning-specific modification of the rabbit's unconditioned nictitating membrane response
B G Schreurs1, M M Oh, C Hirashima
1Laboratory of Adaptive Systems, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892, USA.
Behavioral Neuroscience
|February 1, 1995
Summary
Classical conditioning alters unconditioned responses (URs) even without the conditioned stimulus (CS), a process termed conditioning-specific reflex modification. This learning affects neural pathways for both conditioned and unconditioned stimuli.
Area of Science:
- Neuroscience
- Behavioral Psychology
- Learning and Memory
Background:
- Classical conditioning typically involves learning associations between a conditioned stimulus (CS) and an unconditioned stimulus (US).
- Research has explored how conditioning affects responses beyond the direct CS-US association, investigating phenomena like conditioning-specific reflex modification.
Purpose of the Study:
- To investigate whether robust classical conditioning can modify unconditioned responses (URs) in the absence of the conditioned stimulus (CS).
- To determine if these modifications, termed conditioning-specific reflex modification, are dependent on the duration of conditioning and the level of conditioned responding (CRs).
Main Methods:
- Rabbits underwent classical conditioning with tone (CS) and periorbital electrical stimulation (US) for 1, 3, or 6 days, with paired, explicitly unpaired, or no stimulus presentations.
- Unconditioned responses (URs) to the US were measured for intensity and latency before and after conditioning.
- Conditioned responding (CRs) was assessed to determine the level of learning achieved.
Main Results:
- After 3 days of paired conditioning, conditioned responding (CRs) reached 94%, accompanied by a significant increase in the latency to peak UR.
- This increased UR peak latency was replicated in a second experiment with 6 days of conditioning.
- A conditioning-specific increase in UR amplitude was also observed, but no UR changes occurred after only 1 day of conditioning with low CR levels.
Conclusions:
- Robust classical conditioning induces learning-specific changes in the neural pathways mediating the unconditioned stimulus/unconditioned response (US/UR).
- These findings suggest that conditioning impacts not only the pathways involved in the CS/CR but also those responsible for the US/UR, demonstrating a broader effect of learning on reflex modification.