Discriminative conditioning with different CS–US intervals produces temporally differentiated conditioned responses in the two eyes of the rabbit (Oryctolagus cuniculus).

The conditioned eyeblink response (CR) in rabbits is lateralized to the eye targeted by the unconditionedstimulus (US). However, a contralateral component has been reported during concurrent discriminativeconditioning of the two eyes. The authors investigated CRs produced by both eyes during conditioningwith 2 different interstimulus intervals (ISIs) in which a short conditioned stimulus (CS) was paired witha US to the left eye and a long CS was paired with a US to the right eye. Whether the 2 CSs were moreor less similar (or identical), the short CS produced short-latency CRs in the left eye, whereas the longCS produced long-latency CRs in the right eye. The contralateral responses to a CS trained at one ISIwere separable into temporal corollaries of the ipsilateral response (suggesting a bilaterality of the CR)versus those to a CS trained at another ISI (indicating generalization between the CSs). The resultsindicate that the neuronal substrates subserving CRs of the two eyes involve not only a dominantlateralization but also some avenue of bilaterality.Keywords: classical conditioning, learning, lateralization, cerebellum, timing