A POSSIBLE NEURONAL BASIS FOR REPRESENTATION OF ACOUSTIC SCENES IN AUDITORY-CORTEX OF THE BIG BROWN BAT

BEHAVIOURAL studies1-4 and field observations5-7 demonstrate that echolocating bats simultaneously perceive range, direction and shape of multiple objects in the environment as acoustic images derived from echoes. Cortical echo delay-tuned neurons contribute to the perception of object range, because focal inactivation of these neurons disrupts behavioural discrimination of range8. We report here that response properties of delay-tuned neurons in the cortical tonotopic area of the bat, Eptesicus, transform the sequential arrival times of echoes with different delays into a concurrent, accumulating neural representation of multiple objects at different ranges. The sharpness of delay tuning systematically increases at each best delay in a subpopulation of these neurons while responses to echoes at different delays are accumulated. The resulting concurrent, multiresolution representation of echo delay corresponds to neural implementation of a common representation of images used in computational vision9-11 and may provide the basis for representing acoustic images of multiple objects as acoustic 'scenes'.