The effects of noise exposure and genetic background on auditory-evoked behaviors in larval zebrafish

Thesis (Ph.D.)--University of Washington, 2016-06

Auditory sensitivity and perception can be influenced by extrinsic factors, such as environmental noise, and intrinsic factors, such as genes and arousal. How do these factors interact and influence auditory-related behaviors? I addressed this question in the larval zebrafish (Danio rerio). Zebrafish have been a powerful genetic model species used in the study of development of auditory structures and exhibit a well-studied and robust escape response when presented with a loud acoustic stimulus. I used psychophysical methods to measure auditory sensitivity and perception by observing changes in this behavioral response. In chapter 2, I describe a novel paradigm using prepulse inhibition as a tool to measure auditory sensitivity in larval zebrafish. I show that this paradigm is more sensitive than other behavioral measures used in zebrafish research. Next, in chapter 3, I demonstrate that loud noise exposure leads to a temporary hypersensitivity toward startle-inducing stimuli, whereas auditory sensitivity, as measured using the prepulse inhibition paradigm, is unchanged. I use pharmacological and physiological measures to explore potential mechanisms of this hypersensitization effect. Finally, in chapter 4, I investigate effects of genetic background on auditory sensitivity and susceptibility to noise exposure between closely related individuals and across multiple zebrafish lines. The results of these experiments show large-scale differences in startle sensitivity between wild-type zebrafish lines. I discuss the implications of this data, summarize these findings in a larger context, and discuss future studies in chapter 5.