Do lesions of the superior colliculus affect acoustic orientation in echolocating bats?

Abstract

We made lesions in the superior colliculus (SC) of blinded big brown bats (Eptesicus fuscus) to study the possible role of the SC in the echolocation and avoidance of 0.5 mm and 0.3 mm wire obstacles. The animals were also tested for orienting responses to sound and light touch. Sham-operated bats avoided obstacles and oriented to novel stimuli as well as before surgery. Three bats with SC lesions performed significantly lower in the obstacle avoidance tests, the percentage of flights on which they missed the obstacles being reduced between 3 and 14 percent. Lesions in these animals included damage of the SC and periaqueductal gray (PAG) throughout the rostralcaudal extent of the SC. Five other animals exhibited no significant decrease in obstacle avoidance abilities. Lesions in these bats were mostly confined to the caudal SC. Although other midbrain structures were lightly damaged, we believe that the greater damage to the SC and PAG was responsible for the small but statistically significant decrease of post-operative obstacle avoidance in the three bats.