Effects of a corneal anesthetic on extinction of the classically conditioned nictitating membrane response in the rabbit (Oryctolagus cuniculus)

Rabbits (Oryctolagus cuniculus) were presented with 7 daily sessions of tone-alone training after conditioning. Before the beginning of each of the first 4 extinction sessions, an artificial tear solution or tetracaine hydrochloride was administered to the cornea of rabbits in the control group (n = 6) and experimental group (n = 7), respectively. There were no between-group differences in the percentage of conditioned responses between both groups. However, the amplitude of the conditioned response was notably reduced in the tetracaine group (M = 0.40, SEM +/- 0.216) relative to the control group (M = 1.32, SEM +/- 0.639) early in extinction. Results seem to suggest that although motor output has been found to play an important role in extinction, corneal sensory feedback is not necessary.