Reacquisition after extinction often appears faster than original acquisition. However, data from conditioned suppression studies indicate that this effect may arise from spontaneous recovery and reinstatement of unextinguished contextual stimuli related to the unconditioned stimulus (US). In the present experiments using the rabbit nictitating membrane preparation, spontaneous recovery was eradicated before reaquisition training. US contextual stimuli were controlled by retaining the US during extinction through explicit unpairings of the conditioned stimulus (CS) and US. Attempts were also made to drive the associative strength of the CS into the inhibitory region by differential conditioning and conditioned inhibition procedures. In all cases, reacquisition was very rapid in comparison with a rest control. The results are discussed with respect to their implications for CS and US processing models of conditioning.
Two experiments used classical conditioning to examine transfer of response features specific to the warning interval between a conditioned stimulus (CS) and an unconditioned stimulus (US). Rabbits were given initial training with a stimulus (CSA) in one modality (tone) at a designated interval (e.g., 200 ms). In a second stage, the conditioned response (CR) to CSA was extinguished. Finally, training was shifted to a new stimulus (CSB) in another modality (light) at a new interval (e.g., 400 ms). Compared to rest controls, there was an enhanced rate of CR acquisition to CSB and a tendency for early CRs to CSB to reflect the CSA-US interval. However, the extinction procedure and the change in CS-US interval together reduced these two aspects of transfer across stimulus modalities. The findings are discussed in terms of their implications for theories of cross-modal transfer. A layered network with real-time features is offered.
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