ASA 130th Meeting - St. Louis, MO - 1995 Nov 27 .. Dec 01

4aAB3. Startle reflex in fish.

Peter H. Rogers

Thomas N. Lewis

George W. Woodruff School of Mech. Eng., Georgia Inst. of Technol., Atlanta, GA 30332-0405

Michael D. Gray

Georgia Tech Res. Inst., Atlanta, GA 30332-0810

Directional hearing in fish is a poorly understood phenomenon, whose complexity makes it difficult to analyze. The directional, Mauthner cell mediated, startle response, which does not involve the CNS, is considerably simpler and more amenable to analysis but may still provide insight into the algorithms and mechanisms for more general directional hearing tasks. The startle reflex is modeled and studied experimentally in goldfish. The basic model posits that the initial polarity of both the incident acoustic pressure and particle acceleration measured by the fish's auditory system determines the direction of a threat, and initiates an escape reflex in the appropriate direction. The startle reflex of goldfish is observed experimentally in a large acoustic test tank at Georgia Tech. The subject is placed in the center of the tank, and its behavior is observed using a video camera. The acoustic stimulus is generated using simple spherical sources driven to provide independent control of pressure and velocity waveform, so that, for example, monopole and nearfield dipole fields could be established. A parallel effort was undertaken in order to determine a potentially relevant acoustical stimulus, the field generated by an attacking fish. [Work supported by ONR.]