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Physiological and behavioral studies of rabbit eyeblink conditioning under temporal uncertainty: Purkinje cell response and compound conditioning
The present study employed electrophysiological and behavioral approaches to investigate conditioned response (CR) timing and integration when rabbits were trained with a temporal uncertainty paradigm. The temporal uncertainty paradigm involved training with a mixture of two interstimulus intervals (ISIs) of 300 and 700-ms. Previous work reported that when rabbits were trained using two CS-US, the resulting CRs showed bimodal amplitude peaks (Moore & Choi, 1997). Principle activities investigated in this study included a recordings experiment designed to investigate the expression of CR integration in cerebellar Purkinje cells and experiments designed to provide normative data on CR integration at the behavioral level. The electrophysiological recording experiment investigated the topography of conditioned eyeblink responses in rabbits trained under a mixed ISI procedure is predicted by the conditioned stimulus-triggered firing of cerebellar Purkinje cells. Recordings from Purkinje cells showed that the activity of individual neurons located in the cerebellum fired in a way that reflects the topography of conditioned eyeblink responses. Single neurons fired in anticipation of both amplitude peaks of bimodal CRs, suggesting that integration of learning may be expressed by individual Purkinje cells. Additionally, on short ISI trials the response to the second peak was suppressed suggesting that the US becomes a conditioned inhibitor during training. The behavioral experiments examined compound conditioning under temporal uncertainty and how it presents challenges to various models of learning, such as Sutton and Barto's TD (CSC) model (1990), which are designed to predict the amplitude and timing of complex CR waveforms in eyeblink conditioning. These behavioral experiments specifically examined rules for reconstructing complex CR waveforms from component waveforms that arise for mixed-ISI protocols. Decomposition of compound waveforms preserved the bimodality of compound waveforms, but the overall waveforms were shifted in time resulting in longer latencies than observed compound waveforms. Summation of trained component waveforms, each trained at different ISIs, resulted in unimodal compound waveforms that were also shifted so that the peaks of the compound waveforms were between those of the component waveforms. Combination rules would have fit better if not for the shift in latency that occurred.
Polewan, Robert J, "Physiological and behavioral studies of rabbit eyeblink conditioning under temporal uncertainty: Purkinje cell response and compound conditioning" (2006). Doctoral Dissertations Available from Proquest. AAI3212748.