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Interview with Aage R. Moller Ph.D.

Aage R. Moller, PhD

May 31, 2004
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Author of:

"Hearing: Its Physiology and Pathophysiology"
(ISBN 0-12-504255-8, Academic Press)

and

"Sensory Systems: Anatomy and Physiology"
(ISBN 0-12-504257-4, Academic Press)

AO/Beck: Good Morning Dr Moller.

Moller: Good Morning Dr. Beck.

AO/Beck: Aage, it is an honor to work with you this morning. I recall meeting you in the early 1980s. I was working in Los Angeles and you were in Pittsburgh, and I was just getting involved with intraoperative cranial nerve monitoring. I had the good fortune to observe you in the operating rooms for a few days, and in retrospect that was really a pivotal occasion for me professionally. Frankly, I recall being overwhelmed by how much I had to learn! But more importantly, I remember being so impressed by the pivotal role you played in those surgeries.

Moller: Thank you Doug, that's very kind.

AO/Beck: Nonetheless, it'll probably read better if we start at the beginning. So, if you don't mind, would you please tell me a little about your education? Where did you earn your doctorate?

Moller: I got my doctorate in Stockholm, Sweden at the Karolinska Institute, and that was in 1965.

AO/Beck: And your area of study was auditory electrophysiology wasn't it?

Moller: Yes, well, it's actually physiologic acoustics. And I do have an official title from Sweden, as Doctor of Medicine, although I am not a physician, but that is how they do things in Sweden.

AO/Beck: When did you come to the United States?

Moller: In 1978, I started at the University of Pittsburgh in the department of otolaryngology together with my wife, Dr. Margareta B. Møller, who is an otologist, specializing in vestibular disorders and tinnitus. And then in 1983 I moved to the department of neurosurgery, where I was a professor of neurosurgery.

AO/Beck: And at that time, you produced some landmark papers in intraoperative cranial nerve monitoring and your ABR "site of origin" work that really separated your papers from the theoretical crowd, because your papers were based on real, human analysis, not lab animals.

Moller: Yes, we had some amazing opportunities. A large part of that was because we had a very dynamic surgical team and lots of people that came to us for intra-cranial problems, skull-base tumors and other issues. Because we were doing so much surgery, we had the opportunity to ask some well formed questions and to design studies to develop the answers and of course we pursued some research topics as well. The opportunities available to me in Pittsburgh were very nice and we had an excellent team.

AO/Beck: And then in 1997 you went to the University of Texas at Dallas?

Moller: Yes, I have been here almost seven years and I have a chaired-professorship.

AO/Beck: I suppose we'd better start talking about the books! And I want to state on the record, that these are among the best textbooks I have ever read on their respective subjects! Let's start with Hearing: It's Physiology and Pathophysiology. I know the book was actually published in 2000, but as someone who teaches anatomy and physiology, I've noted that your book is very different from the other texts. Can you tell me a little about how you went about writing it and what is it that separates this book from the others?

Moller: I think the book is different because I actually teach the course for audiologists, and the text is based on the course I teach. It's geared to the audiologist, essentially focused on hearing physiology, not all physiology, not central nervous system or other sensory systems, but really based on the information specific to the areas of interest for the audiologist.

AO/Beck: One thing I'd like to discuss is the subsection on "Hearing With Two Ears." Even though this is a very basic topic, it might be beneficial for some readers to hear your very strong opinions on this topic, and if you could relate your thoughts specifically to hearing aid fittings, that would be great.

Moller: Sure Doug. You know, we don't have two ears so as to have one ear and a spare, any more than we have two legs to have one and a spare! When trying to understand speech in noisy or complex or difficult listening situations, the ears work together to discriminate and clearly hear one person within an environment of many people. In other words, if you want to be able to really pay attention to just that one person in a crowded room, you need the two ears to work together. The ears and the brain work together to compare the spectral, intensity and temporal cues and to make sense of them based on a binaural input. If there is only one input, the sound becomes more noise-like, and one ear by itself cannot really make sense out of it. In vision, you know that if you cover one eye, you have no depth perception. The brain must integrate the signal from both eyes to make sense of the visual image, and it's the same with hearing.

AO/Beck: Another issue you address in the book is one of my all time favorite topics - Electrocochleography (EcochG). I wonder if you would discuss SP and AP ratios for me, and in particular the relevance of the EcochG to inner ear anomalies, such as Meniere's Disease and Endolymphatic Hydrops?

Moller: Yes, this is a very interesting topic. If you are going to compare the compound action potential and the summating potential, people tend to use clicks to elicit this. But clicks are really not the ideal sound. One really should use tone bursts and then the action potential and the summating potential will separate out more clearly, and you'll have a better representation of the summating potential. Another benefit to the tone burst is that it will also yield a better action potential.

AO/Beck: Which tone burst do you recommend?

Moller: Well, there are some clinical issues to consider here, but over 1000 Hz is usually very good. Of course, this will vary a little with the type and degree of hearing loss and the slope of the loss as well.

AO/Beck: Very good. And once you have an accurate or robust AP and SP, do you judge abnormalities based on amplitude or ratio?

Moller: Well, the problem is that whatever you do, it's just not a very good measure of inner ear problems! It has been found that people with Ménière's disease often have an abnormally large summating potential as compared to the compound action potential, but the problem is that a good number of people without Ménière's disease have that same abnormality. In fact animal studies have shown the SP can vary for no particular reason, and it can even change polarity. In the final analysis, electrocochleography does not really do a very good job separating normal from abnormal.

AO/Beck: And what are your thoughts as to doing an EcochG during surgery to help validate an effective endolymphatic sac decompression?

Moller: I am glad you asked that, because that is quite a different situation than the one we just discussed. During surgery, the patient serves as their own control, so you can have multiple recordings from the same person, and then compare them to their own baseline over time as surgery progresses, so that seems to have more validity and more reliability and I think it's a reasonably good indicator of intraoperative changes.

AO/Beck: Very good. Let's speak about the anatomic origin of the ABR and peaks I through V please.

Moller: I feel very comfortable saying that wave I originates from the distal end of the 8th cranial nerve, at the cochlea, and wave II is from the medial end of the 8th nerve. So peaks I and II are simple and easy as they come from the auditory nerve. As you arrive at peak III, it becomes more complicated. Dr Jewett, the fellow who named the peaks, only marked the vertex positive peaks, but there are vertex negative peaks, and they have meaning too! It is likely that the negative peak following the positive peak III is generated in the cochlear nucleus, and I believe III is generated within the cochlear nucleus, and it is a complex structure with many potential generating sites. Peak IV is not constant, and it may or may not be there in a given patient, but when it is there, it is probably generated close to the midline of the brainstem. I believe the sharp tip of peak V is from the proximal or central portion of the lateral lemniscus where it terminates in the inferior colliculus.

AO/Beck: And what really makes your research different from so many others, as I intimated earlier in the discussion, is you placed cotton wick electrodes on the various anatomic sites during brain surgery, and then you recorded the results, with known anatomic correlates, and you could actually witness changes as the electrode moved from location A to location B, that the latency and amplitude changed too.

Moller: Yes, that's correct. Our understanding of how these things work was developed and fine-tuned during surgical procedures on humans, and that allowed us the luxury of really knowing what result occurs from which interaction.

AO/Beck: I believe your group in Pittsburgh was the first to record bioelectrical potentials from the cochlear nucleus, is that right?

Moller: Yes. I think that's correct. And I think that for people without auditory nerves, the new implant system that the House group in Los Angeles has developed is a wonderful option. In fact, it may even find application with congenitally deaf children. You see, their deafness may have to do with very small internal auditory canals, which actually "strangles" the auditory nerve and if that is so, then perhaps the signal cannot get from the inner ear to the brain via their 8th nerve, and the brainstem implant may be an option in selected cases. Dr. Coletti in Italy has explored this and has been very successful with it.

AO/Beck: That really is an amazing idea, and frankly I haven't really thought about that before. Generally I think of congenitally deaf children as having inner ear anomalies, not cranial nerve abnormalities.

Moller: Well yes, I think you're quite correct, and what you just expressed is typical of ENT physicians and audiologists, and that's probably why we haven't fully explored this idea, but it may well be worthy of further exploration.

AO/Beck: I agree - that really is a fascinating idea and I thank you for bringing that to my attention. However, I'd like to switch topics if I may...Can you please tell me about the pragmatic application of middle latency responses (MLR)?

Moller: The real problem with MLR is that they are so variable. I spent a considerable amount of time in Pittsburgh studying MLR potentials, but I never published anything on it, because we just couldn't make sense of it, the variation was amazing. So I am not sure if there is a pragmatic "real world" application at this time, although some authors have done sophisticated research studies and found meaning there. As a clinical tool, I am not sure if there is an application at this time, beyond measuring frequency specific thresholds.

AO/Beck: Aage, the time is going by very quickly, and I would like to also address a few topics from your 2003 book "Sensory Systems: Anatomy and Physiology." If you can give me just a few more moments, that would be great.

Moller: Certainly, please go ahead.

AO/Beck: Your book takes a very different approach to sensory systems. In fact, your book takes a more global approach than the texts I have read before. Can you comment on that?

Moller: Yes, well thank you for that. That was indeed the issue while writing the book. You see most books look at the sensory system of this, or that, and they speak about other anatomic and physiologic systems such as vision, or hearing, or somatosensory, and then the related sensory systems which makes it harder to appreciate and learn about. But indeed there are many commonalities between the different sensory systems, so I organized it a little differently, and perhaps that makes it easier to grasp the concepts and basics of sensory systems.

AO/Beck: What is your sense of the weighting typically found in neuroscience text books as it relates to the nervous system versus sensory systems?

Moller: Well, I think there is too much focus on the sensory organs, and relatively little is said about the nervous system, and so in my book I have tried to balance this a little more equitably.

AO/Beck: Can you please address the issue of Classical ascending and classical descending pathways?

Moller: Yes, thank you for asking. This too is an area that is missed in many, in fact most books. They address the classical systems, but there are other systems too, and they are sometimes parallel systems, referred to as the "non-classical" systems, and they are important, but we don't know or teach much about them. If you think about the classical and the non-classical systems in terms of the auditory system, you can appreciate the non-classical systems that exist in all systems. The main difference in the auditory system is that the classical system uses the ventral portion of the thalamus, and the non-classical uses the dorsal portion of the thalamus. Another difference is that the non-classical system will respond to more than one sensory modality. Whereas in the classical auditory system, the cells only respond to sound, not to touch and not to light. This is an important difference because in the non-classical systems, cells will respond to other modalities.

AO/Beck: Can you please give me an example?

Moller: Certainly. For example, in the auditory system, using the non-classical system, you can modulate the auditory response by stimulating the somatosensory system. And so, the perception of sound can be altered if you stimulate the somatosensory system, and this works in children, but the effect decreases with age. And this may have application for tinnitus patients too. In other words, if you stimulate their median nerve, the tinnitus may decrease. So the point is that the non-classical systems are important and they offer alternatives and options for us. But of course, to use these options, we need to know they exist!

AO/Beck: And this same phenomena can be used for pain management?

Moller: Yes, it can and it is used for pain management.

AO/Beck: Dr. Moller, it is always a pleasure speaking with you. Thank you so much for your time and knowledge, and again, I want to urge the readers to read these two books, they are fascinating and enlightening.

Moller: Thank you too Dr. Beck. It has been a pleasure speaking with you too.

4 recorded webinars | Millennial Matters & Generational Issues in Audiology | Guest Editor: Yell Inverso, Aud, PhD |


Aage R. Moller, PhD

University of Texas at Dallas, School of Behavioral and Brain Sciences, Callier Center for Communication Disorders