Red nucleus and eyeblink conditioned response in rabbits

ABSTRACT

The role of red nucleus [RN] in the acquisition of rabbit eyeblink conditioned response has been a controversial issue. In the present study the effect of an RN lesion and changes in RN electrical activity during eyeblink conditioning have been investigated. Eighteen male albino rabbits, 1.5 to 2 kg in weight, were used. Animals were divided into four groups The RN lesioned group which received a contralateral RN electrical lesion [2mA, 15 sec], the sham operated group, the electrophysiological group in which recording electrodes were implanted in the contralateral RN, and the intact [control] group. Rabbits received training for classical conditioning of the eyeblink response. A tone was the conditioned stimulus and an airpuff was the unconditioned stimulus. Our data shows that in the RN lesioned group eyeblink conditioned and unconditioned response amplitudes were significantly lower than the control and sham operated groups. Also the percentage of conditioned response incidence was decreased in the lesioned group and the latency of unconditioned response was significantly greater than the other two groups. In the electrophysiological group, RN rhythm was increased during learning. In conclusion it seems that the output of RN is capable of modulating the pathways mediating both conditioned and unconditioned responses