Abstract

Latent Inhibition(LI) is a phenomenon in which the preexposure to a conditioned stimulus(CS) retards the subsequent association between the CS and unconditioned stimulus(US). In the present study, LI phenomenon was investigated with the eyeblink response conditioning of the rat. To record the electromyograph of the obicularis oculi muscle and to deliver US, 4 electrodes were implanted in eyelid muscle. The rats were classically conditioned in a Pavlovian delay paradigm with a 350msec tone CS (2.8kHz, 80dB, sine wave) and a 100msec periorbital electrical US shock (100Hz, 0.5~2.0mA, square wave). After 1200 CS preexposures, LI group were conditioned. The control group were conditioned without the preexposure to CS. The conditioning continued daily for a total 10 sessions (800 trials). LI was observed in LI group compared to the control group. The CR size, CR latency and other results were not significantly different between the both group. The study of LI with rat eyeblink conditioning has advantage since it can be compared with the LI results of the other behavioral tests. The present result verified that the eyeblink conditioning of rat can be applied to LI study.