(full paper is archived in the Miller Library)
Title: Startle-response potentials in the
retina and optic tectum of adult zebrafish
Student Author(s): Gu, Emily
Faculty Advisor(s): Thompson, Stuart
Location: Final Papers Biology 176H
Date: June 2006
Abstract: Although the functional role of the optic tectum has yet to be well characterized in teleosts, it is thought to be responsible for initiating and coordinating visuomotor behaviors associated with the looming response. In this study, behavioral and electrophysiological responses to the looming stimulus were measured by differential suction electrodes at the optic tectum and retinal ganglion cells of adult male zebrafish (Brachydanio rerio). The looming stimulus was simulated by a light-emitting diode and by increasisng irradiance durations. Responses to off-light events were found at both the retina and optic tectum, suggesting that light-induced startle responses begin as early in the visual synaptic pathway as the retina. However, several differences in signal shape and amplitude between recordings at these two regions suggest that higher-order visual processing of on- and off-responses occurs at the optic tectum. Latency times were measured between the presentation of the stimulus and the onset of the response, but data are currently inconclusive. Habituation was observed through decreases in startle response as a function of flash repetition. Future studies are necessary to correlate electrode position with signal strength to resolve neural organization at the optic tectum. Other parameters such as flash duration, interstimulus interval, and age of the zebrafish can also be varied to obtain a more complete understanding of the startle response.