specific aims

I am currently working on writing a NIH F31 predoctoral training grant. Writing the grant is an assignment for my research and ethics course, however, seeing as how tight funding is, I think I will try to submit the grant this summer. I'm putting together the specific aims part of the grant now, which is basically the hardest part. The proposal I am submitting would support my dissertation research. The following is a brain dump...

Otoacoustic emissions are sounds that originate in the cochlea that can be measured in the ear canal with a sufficiently sensitive microphone. Kemp made the first recordings in 1979, and since their discovery, otoacoustic emissions have been used to investigate an objective approach to measuring auditory sensitivity. In other words, right now, clinicians must rely on behavioral (subjective) measurements to test hearing thresholds, and finding an objective measurement could be described as one of the holy grails of hearing research. We have made some strides in our knowledge of the physiological mechanisms which underlie otoacoustic emissions (OAEs), but we are still far from having a thorough understanding.

Traditionally, OAEs were classified based on the type of stimuli that was used to evoke them (ie- pure tone, broadband, no stimuli), and is has been thought that OAEs (of all types) arise from the outer hair cells, or as a by-product of some action of the outer hair cells. However, in recent years, however, it has been suggested that all types of emissions are the result of a complex interaction between two generation mechanisms, "place-fixed" and "wave-fixed". The relative contribution each of these makes might be dependent on the type of stimulus used to evoke the OAE. The type of emission I am interested in is what is known as the stimulus-frequency OAE (SFOAE), which is an emission evoked by using a pure tone stimulus (seen to left).

Zwieg & Shera (1995) presented a model of SFOAEs called the Coherant Reflectance Filtering Theory, which argued that SFOAEs are dominated by energy from the peak of the traveling wave. In other words, there are random pertubations along the basilar membrane, it is not smooth, and these pertubations reflect energy back to the middle ear. In the case of a pure tone stimuli, the energy reflected back is dominated by the relatively small range of random pertubations from the traveling wave envelope. If this is the case, the model predicts that the delay of the SFOAE measured in the ear canal represents the time it takes the energy to travel from the ear canal to the peak of the traveling wave and back to the ear canal, which is approximately 1.5-1.7 times the delay of the energy to travel from the ear canal to the peak of the traveling wave. If this is correct, then SFOAE might represent a good, noninvasive estimate of basilar membrane travel time, and might have implications for the clinical investigation of cochlear pathology.

Siegel, et al. (2004), however, found substantially shortened group delays in chinchilla, and also found that by adding a high frequency suppressor tone, amplitudes of the SFOAEs were reduced. He argues that his results suggest a distributed region of generation, rather than a localized region of generation as Zweig & Shera propose.

We will explore the spatial generation site of SFOAEs in at least two species of animals. We will record SFOAEs before and after damaging the base of the cochlea . The specific aims of the study are:

(1) to determine if the amplitude of the SFOAE decreases after traumatization. If the SFOAE is generated from a distributed region of the cochlea, the amplitude of the SFOAE will decrease.

(2) to determine if the group delay of the SFOAE increases after traumatization. If the SFOAE is generated from a distributed region of the cochlea, the group delay of the SFOAE will increase.

Preliminary results (to be presented at the 2007 meeting of the American Auditory Society) do not support either hypothesis. In other words, our results to date support the predictions of CRF theory, or that the SFOAE is generated from the tip region of the traveling wave.

(3) repeat Siegel's experiment to explore extraneous factors that may have led to his result of shortened group delays and decreased amplitudes with the addition of a high frequency supressor tone.

ok... dump complete... still need to work on expressing this in a more concise fashion, and come up with some "payoff" paragraph. I think grant writing must be one of the more difficult things we do in research. This grant will be critiqued by someone who knows very little about this area as well as an expert. Yikes... I am working through a chapter in a grant writers workshop book that was given to me in class. I think I will purchase one; it does seem to be very useful.