well, maybe not

read the Zweig, 1991 paper yesterday and today in an attempt to parse the current model, including the wave equations. wow. i think i'm starting to get bits and pieces, but this might be one of the most difficult reads i've thus encountered.

in an attempt to simplify, i'd like to start working on a flow chart just to see the basic elements i need for the model. unfortunately, this is easier said than done. this is one of my biggest problems. i can understand concepts, and maybe even describe them to someone (even outside of my field), but putting it all on paper is highly frustrating. grr...

modeling

I've been hard at work at the questions I addressed in my last blog. So far I've figured out a few things...

some assumptions of the CRF model:
The model is linear, and therefore assumes validity only in the low-level linear area near the threshold of hearing. This is interesting because I am actually testing the model using a broad range of intensity levels, meaning much of what I measure will not be fully incorporated into the current model. I'm going to have to try to add this into the flowchart of the model somehow.

The model assumes that there is spatial dependence- in other words the cochlea has a frequency/space mapping. This is a pretty standard component of any cochlear model, but it means that I have to figure out the wave equation. I'm planning to do some major thinking and researching this weekend. Rob gave us a model he is working on, and I plan to use it as a starting point. Hopefully by next Friday I will have made significant strides.

The model assumes a long-wave approximation. Shera tested this assumption in 2005, and I'm in the process of working through his conclusions. The basic conclusion, however, is that this is not a terribly off assumption.

The model assumes the mechanical properties of the cochlear partition vary irregularly with position. This is consistent with previous arguments.

I've also been working through the equations dealing with R. This is somewhat related to the other project we have been working on in middle ear (which is another blog topic altogether). I've been looking at the SFOAE profile v. frequency and looking at the regular oscillations present. It's pretty obvious to me now that these are standing waves, and they are coming from the cochlea/stapes area. Yes, it all comes back to impedance.

I've found a few more papers to read and will update on my progress again soon.

I also have a far better understanding of the opposing research. Siegel used a "suppressor" tone far basal from the stimulus in order to eliminate the base of the cochlea as a contribution source. He used a tone far enough away from the area of measurement that the suppressor isn't truly suppressing, but it's doing something. I have my suspicions about what it's doing, and I've added a new test to my protocol. I really can't wait to get back into the booth to put all of this to the test.

My goal for this weekend is to put all of this together, and do a little Matlab coding to test out my ideas.

back to business

First, a Cooper update: How cute is this baby?!?! Every time I see a new picture of him, he gets a little less baby faced and a little more toddler. He is really starting to look just like Jim, and it seems he has also inherited Jim's love for baseball. I'm hoping to head home in a few weeks for a visit. Miss you, buddy!

Had a nice break and visit with my sis, but now I've got to get back to work...

we're making a presentation in Rob's phsyiology class about how we can incorporate modeling into our research. This isn't a difficult question for my research because I'm basically testing the predictions of a popular model, so I've got the basic idea for my presentation nailed down. Now come the nuts and bolts. Here's the thing... I'm NOT a mathematician, so delving into the math in the model I'm testing is giving my brain a huge workout.

The big questions I'm working on answering in regards to the theory of CRF are:
What are the major assumptions in the model?
How is cochlear reflectance (R) calculated, and how does this relate to the middle ear sound pressure recordings?
What is Bragg scattering, and how does this relate to R?
What are the major parameters in the model, and can they be represented?

The other part of my presentation will focus on research that has been done that contradicts the predictions of the CRF model, ie group delays measured in chinchilla when a suppressor tone is added to the recording paradigm are much shorter than CRF would predict.

The big questions I'm working on answering in regards to this research are:
Is the method in which the researcher calculates group delay underestimate delay?
How can suppression alter the basilar membrane excitation pattern?

This modeling project has been (thus far) extremely useful in terms of gaining a more in depth understanding of the background of my research. I'm pretty certain that a good part of the introduction/background for my dissertation will come out of this project. Excitement!!!

family fun

Spring break has arrived, and what could make for a better vacation than a visit from your little sister? My "baby" sister Brittany is up for a visit from Florida, and we are having a wonderful time. I haven't seen Brit in almost three years, which boggles my mind. I'm very happy that she was willing to travel up here to see us, even as she is about to become a mommy. I think she is going to be a wonderful mother, and we've spent a lot of time so far in her visit talking about her perspective on parenting. I'm very proud of her, and I seriously love being an auntie.

We had a nice visit with our aunts and uncles, long overdue. Ray pulled out some slides, and we took a little walk down memory lane. It was so strange to see some of the pictures in the slideshow. They were all quite old, taken long before my sisters were born, but there were still many things that I remembered. The old brown chair my great-grandmother always sat in, the huge television set at my grandfathers house, Christmas when I was a toddler... it was very surreal. Mike was trying to be cool, as usual, and failing, as usual.

I have a lot of work to catch up on this week. I need to catch up on my statistics homework, review specific aims for my classmates, read a lot, and start working on my modeling project. I'm starting to formulate some ideas, but I really need to sit down and chart it out.

Final days of AAS

We had a wonderful time in Arizona. Rob's talk was well received (considering it was finished less than an hour before the presentation time). Doug Keefe did comment on why was Rob giving the talk and not me (since I was listed as first author), Rob started his talk with a joke in that he was third author, he was the least important, and therefore was made to talk by the rest of us. Heh...

The closing reception was held at the Phoenix art museum, which was nice, but had a bit too much "American" art for my taste (I prefer classic religious art). They had a Dutch Masters exhibit running, but it was a pretty small exhibit for an 18 dollar price tag.
About 30 seconds after I took this picture (you can't really tell, but it is a bunch of hanging pieces of charred wood), a security guard came and insisted on searching my bag. I thought he'd tell me I wasn't allowed to take pictures, but then he said a nearby sculpture had been lifted, and they were locking down the museum to try to recover it. Seriously, who steals art? Thankfully, whoever it was, they were caught, and I assume now in BIG trouble.



In addition to the mystery theft, we had the opportunity to meet a very nice researcher from Poland, who was teasing Rob for picking on a young female student at her poster. She told him that he was too critical of her, and he could intimidate her out of continuing her studies. I think she was very frank (which I like, she reminded me of my aunt Anna), and I know Rob appreciated her comments. However, I'm not in total agreement. I worry about how women can be perceived as weak, frail creatures, especially in a time where we are all supposed to be equal. Besides that, I was quite looking forward to tough questions and critiques for my poster. Perhaps this it because I've been trained by Rob, who values this in our training. I have to say that part of presenting my work is looking for ideas that I missed, and this comes from people being extra critical. I feel very lucky to have Rob as my mentor, and I know, especially now, that I will be well prepared for a career in science when I leave IU. Rob has truly taught me the importance and joy of quality research, and of course recruited Kelly into the lab! Way to be the smartest guy around, Rob!
I am also grateful to the program committee of the American Auditory Society and to the NIH for awarding me a Mentored Student Travel Award so that I was able to make this trip.





With that I say goodbye, Arizona! See you next year!!!

A Polish legend

I had the unique and wonderful opportunity to be present as a very famous Pole received a very distinguished award at this meeting.

Dr. Jozef Zwislocki is a native of Poland, whose family escaped in 1939. He holds degrees in electrical engineering and an Sc.D. in technical sciences at the Federal Institute of Technology in Zurich, Switzerland. He taught and conducted research for more than 35 years at Syracuse University, retiring in 1992 as Distinguished Professor of Neuroscience at the Institute for Sensory Research (ISR). He is recognized as one of the world's leading auditory researchers, with a teaching and research speciality in the auditory system and its psychophysics, biophysics, and psychophysiology.

In 1958, the ISR was established under his direction at Syracuse University. In 1970, he invented the "Zwislocki Coupler," an artificial ear that determines the amount of current needed in an earphone to produce a particular sound intensity at the eardrum. This is among his 12 patents in hearing aid technologies. More recently, he has invented a sound muffling device for industrial application.

As a part of the award presentation, it was very exciting to see his colleagues from Poland giving him their thanks and appreciation. Many researchers from Poland made a very long journey to present him with a beautiful framed photograph of his family with his grandfather, who was perhaps the greatest president in Poland's history. Dr. Zwislocki gave a wonderful speech in which he told a story of having recently been fit with hearing aids, and how he recognized some of the procedures still used today in clinical audiology were those he had invented. We all thank Dr. Zwislocki for his many wonderful contributions to our field, and are honored to have "shared air" with him.

AAS day three, a day late

Here are some pictures from yesterday! The poster was well accepted (although I missed my photo op, so I'll take a pic when we get back). Had a great meal with Rob, Kelly, and Larry Humes at a little place in downtown Scottsdale. Wonderful Italian food, with FRESH YUMMY fish!!! mmmm.....

AAS day two

We had a pretty great day today here in Scottsdale. Attended some good talks and some not so good talks, and I am really enjoying the weather. The posters are tomorrow, and while I'm looking forward to it, I'm getting just a little bit nervous. I got crap for sleep last night, and I really hope that I sleep well tonight. Tylenol PM here I come... I also made a huge mistake and tried to walk around in my heels all day, and got what I think is the hugest blister I've ever had in my life. See?

ahhh, the desert...

I love Arizona. I'm here in Scottsdale for the second time to attend the American Auditory Society meeting. This is where I spent my afternoon (meeting starts tomorrow). I will present my poster on Monday, and I will try to upload some more pictures as we go.

missing mom and lions

My mom played her new composition for me the other night. Although listening to her through a cell phone sucks, it is probably my favorite thing she's ever written. Mom is so amazingly talented, it's sick. I miss the piano and being surrounded by music all the time. I know I should attend more events at our music school, but in a way, it just makes me miss mom more.

In other news, I recently recieved a scholarship from the Lion's Club. This is an organization I intend to be a part of someday. They are doing wonderful work, and give a lot of support to Speech and Hearing. Here is a really goofy picture of me recieving the award. I really take horrible pictures, don't I?

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.

Why didn't you just say that?

I'm taking this multiple linear regression course this semester, and I'm slightly annoyed by it. Rather than use software that some of us might have used before (SPSS, R, Matlab, etc), the instructor decided to use something that no one uses (including himself). Ok, experimental, I can deal with that. However, this software has absolutely no manual, user help site, message board, nothing. The textbook is supposed to act as a user guide, but is written in such a way that it is nearly impossible to find what you are looking for. Grr... throw me a bone here, people.