Representing Space Through Sound

Cynthia F. Moss
Johns Hopkins University

Abstract: Spatial navigation by echolocation depends on the dynamic interplay between auditory information processing and adaptive motor control.  An important component of this adaptive system is the timing of sonar signals, which the bat adjusts, not only with respect to object distance, but also in the context of perceptual demands and planning. For example, the big brown bat, Eptesicus fuscus, produces stable groups of sonar signals, flanked by longer pulse intervals, when it is challenged by spatial tasks, such as figure-ground segregation and target trajectory uncertainty.  This talk will summarize behavioral and neurophysiological findings, which indicate that the big brown bat's control over sonar call timing serves to sharpen its spatial representation of the environment. Behavioral studies were conducted in the laboratory and the field, as the bat tracked insect prey under a variety of conditions.  Neural recordings from the midbrain superior colliculus of freely behaving animals show that auditory responses to echoes are modulated by the bat's production of sonar sound groups.  Collectively, these data suggest that the bat temporally organizes its echolocation calls into groups, as an active strategy to build a detailed representation of the sonar scene.

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