Summary: In Case You Didn’t Hear

This summer I have worked on a research project with the aim to develop a method to consistently damage zebra finch hearing.  This is a short term goal for the larger project of assessing whether removing SARM 1 (Sterile Alpha and TIR Motif Containing Protein 1) will prevent hearing loss or promote healing.  SARM 1 is a protein responsible for initiating axon degeneration in the neuron which is thought to be a cause for sustained hearing loss.

As seen throughout my posts, this summer has been focused on inducing hearing loss in zebra finch by exposing them to loud noises for extended periods of time.  I began by exposing them to 90dB of sound for an hour and have increased that to 120dB for 2 hours.  I have exposed zebra finch to various patterns of noise also, whether a white noise, intermittent broadband noise or a pure tone. Thus far it seems that to induce hearing loss sufficient to damage the neurons and induce axon degeneration will require slightly more than what I have tested so far.

The louder and longer I have exposed zebra finch to noise, the more significant their hearing loss on average.  The broadband noise appears to work well and the pure tone appears to produce a similar result, while the intermittent noise may produce slightly less hearing loss.  Thus in the future I will continue to increase the dB level and/or duration of the noise and use both a pure tone and broadband noise.

I have been using ABR (Auditory Brainstem Response) to conduct a hearing test on the zebra finch. These hearing tests allow me to track the loss and recovery of hearing ability in zebra finch over time after inducing hearing loss with the noise event.  These tests following the noise event are compared to each other and to a hearing test conducted prior to the noise event.

Throughout the summer the techniques used to perform ABR improved as they were adjusted and our data has hence become more reliable.  There is still room to grow in the consistency of the ABR recordings, such that the amplitude becomes a trustworthy measurement. For now, the amplitude is looked at for patterns, but the  latency of the brain wave response to a sound stimulus is sufficiently consistent to use as our primary data for comparison.  A higher latency value indicates that the brain takes a long time to respond to the stimulus.  Thus, a high value indicates worse hearing than a low value.  The latency from each trial was used to determine which birds experienced hearing loss and the degree of that hearing loss.

Moving forward with this research this semester, I will continue similar experiments to find the optimum conditions for inducing hearing loss.  Then I will begin establishing birds that are genetically modified to not produce SARM 1.

Thanks for reading!