I'm interested in understanding how the bat's sonar works and how the bat's brain makes sonar images. They make sounds, listen to echoes, and then see objects. To study echolocation, we go into the field and videotape bats using sonar for different purposes. These observations tell us in what situations bats use their sonar, and what sorts of sounds they use. If we know where the objects are in the videos, we can figure out what sounds get back to the bats.
My laboratory studies the biological sonar systems of bats, in recent years using the big brown bat, Eptesicus fuscus, as the example. Eptesicus is a species that emits ultrasonic, frequency-modulated (FM) echolocation sounds and exhibits unusually sophisticated real-time signal-processing techniques for auditory representation of FM echoes. I am interested in orientation by echolocation and the neural mecha¬nisms for perception by acoustic images that have evolved in bats, especially FM bats because the theoretical basis for understanding the bat's performance is made unusually strong by the large applied-math literature on radar and sonar receivers. The principal goal of my work is to learn how echolocation "works"to understand how natural images are created in perception from neural reconstruction of the target scene by the bat's brain.
JAMES SIMMONS, PHD, MA
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