The experiments described in this thesis examined post-extinction recovery phenomena following classical conditioning in the rabbit. The first series of experiments examined the rate of reacquisition to the original conditioned stimulus (CS) and to a cross-modal CS following various amounts of extinction. In both the rabbit nictitating membrane (NM) preparation and rabbit heart rate (HR) conditioning, there was a graded reduction in the rate of reacquisition as a direct function of the number of extinction trials. In the rabbit NM preparation, there was also a graded reduction in the rate of acquisition to a cross-modal stimulus (CSB, e.g., light). However, concurrent recovery of responding to the original, extinguished stimulus (CSA, e.g., tone) during training with a novel, cross-modal stimulus (CSB, e.g., light), appeared uniformly robust even following extensive extinction. The second series of experiments examined the conditions necessary for concurrent recovery to occur in the rabbit NM preparation. The introduction of CSB-US pairings resulted in strong recovery of responding to CSA, while the reintroduction of the US alone failed to result in any discernable reinstatement of responding to CSA. Concurrent recovery was specific to the trained and extinguished CSA, with virtually no generalized responding to a novel cross-modal test stimulus (CSC). However, pretraining with CSB-US pairings significantly reduced the amount of recovery to CSA during subsequent CSB???US pairings. The third series of experiments revealed that concurrent recovery was specific to the extinguished stimulus (CSA) with only moderate generalization to other familiar but untrained stimuli in the same modality as CSA. Together these results indicate that concurrent recovery is not primarily the result of the unmasking of the original CSA-US association. Rather, concurrent recovery appears to be at least partially the result of learning-dependent generalization. However, in order for responding to CSB, to generalize to CSA, CSA must have been paired with the same US which is subsequently paired with CSB. Thus, the CSA-US association must be partially intact for concurrent recovery to occur. A layered network model with multiple hidden units is able to simulate rapid reacquisition, facilitated cross-modal acquisition and concurrent recovery.
| Identifer | oai:union.ndltd.org:ADTP/225861 |
| Date | January 2005 |
| Creators | Weidemann, Gabrielle, School Of Psychology, UNSW |
| Publisher | Awarded by:University of New South Wales. School Of Psychology |
| Source Sets | Australiasian Digital Theses Program |
| Language | English |
| Detected Language | English |
| Rights | Copyright Gabrielle Weidemann, http://unsworks.unsw.edu.au/copyright |
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