Comparison of auditory and visual conditioning stimuli in delay eyeblink conditioning in healthy young adults

Classical eyeblink conditioning (EBC) has been widely used to probe cerebellar function in humans and nonhuman mammals. Although the neural pathways governing behavior in this task are well understood and fairly discrete, it remains unclear in the human literature how conditioned stimuli (CSs) of different modalities (e.g., visual and auditory) influence the exhibition of conditioned responses (CRs). In the present study, therefore, CRs to a visual CS and an auditory CS were examined with the single-cue delay EBC procedure. An initial experiment (N=61) was conducted to identify visual and auditory stimuli that had equal perceived intensities. Using these perceptually equivalent stimuli, a second group of 25 subjects completed auditory and visual EBC procedures in two testing sessions 5–8 days apart. Whereas the acquisition of CRs was similar between the CS modality conditions, the timing of the CRs differed such that earlier CR onset and peak latencies were associated with the visual CS. In addition, CR timing improved across testing sessions, as indicated by the later CR peak latencies exhibited during the second testing session, as compared with the first.     

The influence of olfactory context on Pavlovian conditioning and its expression in preweanling (16-day-old) and adult rats

In a series of experiments, we tested the responses of preweanling (16 days postpartum) and adult rats to a specific olfactory context that was present during conditioning and testing of a brightness-location aversion. The first set of experiments established that (1) contrary to previously published effects with other distinctive contexts during conditioning and testing, a novel olfactory context impaired conditioning and its expression in preweanlings; (2) if the preweanlings were previously familiarized with the olfactory context, its presence impaired neither conditioning nor its expression; and (3) although conditioning in the absence of the olfactory context was equivalent for adults and preweanlings, the novel olfactory context had no effect on conditioning or its expression in adults. In the next set of experiments, we tested whether a conditioned aversion had been formed to the olfactory context. It was determined that although preweanlings acquired a substantial aversion to the olfactory context, whether novel or familiar, adults gave no indication of conditioning to the novel olfactory context. A final set of experiments established that preweanlings acquired an association between (or unitized) the CS + and the context. These results add to previous indications that preweanlings may be especially sensitive to redundant or irrelevant features of the conditioning episode.