Neural Mechanisms for Target Ranging in an Echolocating Bat Eptesicus fuscus
We have concluded a series of behavioral, anatomical and physiological experiments in order to gain a better understanding of the neural basis of target ranging in Eptesicus fuscus. Behaviorally, we were interested in learning whether or not binaural integration is essential for ranging. We trained two bats to perform range discrimination using two-choice paradigms (Simmons, 1973) until they reached a criterion of 85% correct responses. We then observed their performance under intact conditions and when one ear was occluded. Occlusion was effected by inserting silicone grease to fill the ear canal of the selected ear. The performance of these two bats under monaural and binaural conditions is shown in Table 1. We found that the performance under monaural conditions was not significantly different from that of intact conditions (p<0.05, Hoel test for the difference of two means). Thus, bilateral interactions, which are essential for encoding directional information about the target, are not required for ranging in this species. Instead, time or intensity information from target echoes is more important for ranging.
KeywordsAuditory Cortex Inferior Colliculus Target Range Intact Condition Bilateral Interaction
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