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Interview with Nina Kraus Ph.D., Northwestern University

Nina Kraus, PhD

June 20, 2005
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Topic: Neural Plasticity, Auditory Neuropathy and BioMAP
Nina Kraus, Ph.D., Hugh Knowles Professor, Departments of Communication Sciences, Neurobiology & Physiology, and Otolaryngology; Director of the Auditory Neuroscience Laboratory; Northwestern University

Beck: Hi Dr. Kraus. Nice to speak with you again!

Kraus: Hi Dr. Beck. Thanks for the invitation.

Beck: Nina, I think many of the professionals will be familiar with your name through your prolific writing of chapters, articles and your many presentations. Before we get to today's topics, would you please tell me a little about your professional education and history?

Kraus: Certainly. Doug, I earned my bachelor's degree at Swarthmore College in 1976, and I earned my Ph.D. at Northwestern University in 1980. My dissertation was on the plasticity of single neurons in the auditory cortex associated with auditory learning.

Beck: So, your background includes both biology as well as neuroscience?

Kraus: Exactly. My training was initially in biology, and I became interested in neuroscience as the years progressed . One issue that continues to fascinate me is the biological underpinnings of auditory learning. How can biology inform us so that we enhance the learning process of languages, music, or even the lectures and conversations in which we participate? From another perspective, how can better learning impact rehabilitation and communication in clinical populations?

Beck: I believe auditory learning is the basis of all learning for people with normal and near-normal hearing, so this is an enormous area! But you are thankfully more focused...and I think back then you were working in particular with single cell responses?

Kraus: That's correct. At that time we knew that populations of neurons changed their response properties over time with learning, particularly once the stimulus became significant. We evaluated single cells in a classical conditioning experiment, in which a particular tone would become behaviorally significant to an animal.

Beck: And you found?

Kraus: Doug, we found changes could occur in single cells, and this was significant and clear-cut. Single cells changed their response to an auditory stimulus once the animal learned to associate the sound with an event in its environment.

Beck: And this helped prove the presence of auditory neural plasticity and it helps establish behavioral correlates with the physiologic phenomena.

Kraus: Yes, that's correct.

Beck: Nina, if you wouldn't mind, can you give me a brief history of your relationship with auditory neuropathy?

Kraus: I got involved with auditory neuropathy in the late 1970s while I was working with a ten-year-old child. He was obviously bright, but he was doing terribly in school, particularly in noisy situations. He was just not able to understand what was expected of him. I recall telling the parents that as best we knew his hearing, acoustic reflexes and tympanograms were all normal...but that the child was clearly not processing sound or speech in a normal way. We performed an ABR to investigate his central auditory pathway, and saw that there was no response, even though he had normal pure-tone thresholds. That was how I first became interested in AN from a central auditory processing perspective. It took three years to get that first paper published,-the reviewers did not believe it was possible to have a normal audiogram and no ABR- but we finally published the paper in 1984.

Beck: What are your thoughts on cochlear implants and AN?

Kraus: At first it was thought that cochlear implants could not work with kids diagnosed with AN...but we know now that there have been children implanted who have done well, and we know there are many variations of AN, and we also know that each child and each situation is unique, so we cannot paint them all with the same brushstroke.

Beck: Agreed. And you had a different name for auditory neuropathy...I know some people use auditory de-synchrony, or dys-synchrony, but you had another term?

Kraus: Right, we called it Brainstem Auditory Processing Syndrome, or BAPS...but the name is not important. I think auditory neuropathy (AN) is the one most people understand, and that's the one I use.

Beck: OK, and I guess AN is mostly a pediatric diagnosis?

Kraus: Yes. There are adults in the AN pool, but since the communication problems associated with it are so pervasive, clinical advice is generally sought in childhood.

Beck: What is the most probable anomaly that creates, causes or initiates AN?

Kraus: The hallmark of AN is the absence of an ABR in a person with hearing good enough to have an ABR -- generally speaking. The ABR is a far field evoked potential, consisting of rapidly occurring synchronous neural events ... with AN it appears to not be there. So the normal neural synchrony required to generate an ABR appears to be missing.

Beck: Nina, could you tell me your thoughts on how background noise combined with abnormal neural synchrony affects behavioral performance?

Kraus: The ability of AN children to listen breaks down particularly in noisy backgrounds. We believe that the presence of background noise prevents the AN auditory system from achieving any form of neural synchrony. On the other end of the spectrum, behavioral deficits in noise are also seen in certain children with learning problems. In fact, noise-related deficits exhibited by learning disabled subjects have shown correlations with abnormal auditory cortical responses measured in noise. Some of the behavioral and physiologic similarities shared by AN and learning disabled subjects has led us to think that these two clinical populations may form a continuum with respect to brainstem timing deficits. That is, neural synchrony disorder is common to both of these subject populations, with AN exemplifying the most extreme cases. We have recently published our conceptual framework (TRENDS In Neuroscience, 2005), which speaks to the existence of different encoding mechanisms for signals in noise.

Beck: OK, please tell me about the BioMAP that I read about a few months ago?

Kraus: Bio-logic Systems Corp. and our lab at Northwestern University are working together to create a commercially available neurotechnology - to evaluate children via neuro-bio-electric (Nina I do not know this word, is it common??) analysis as it relates to auditory processing disorders (APD).

Beck: And so in essence, you guys are examining neurophysiologic events in response to speech stimuli, to see if there is a pattern of auditory responses consistent with APD?

Kraus: Right. We have tested over 1000 kids through our project called "Listening, Learning and the Brain", research that has been funded by the NIH. Basically, the BioMAP is the culmination of a decade of research and will enable us to go the next step. As scientists, we all hope to have the opportunity to explore the pragmatic benefits of basic research, and this is our chance to do so. APD appears to have a neuro-bio-electric basis, at least in some children, and this may lead to objective diagnostic and rehabilitative opportunities for people with APD.

Beck: Does this relate to learning problems too?

Kraus: Yes. We're talking about some 6 to 8 percent of all children in public and private schools. Learning disabilities, dyslexia, ADD, ADHD, CAPD and APD are potentially all impacted by this work and so the clinical and social applications are enormous. Traditionally, behavioral measures have been the mainstay in the diagnosis and management of the child, but our neurotechnology, the BioMAP, is an objective test in which the kids are only passively involved as we measure their auditory bio-electric signals.

Beck: Any idea as to what the bio-electric deficit may be?

Kraus: Yes Doug, we do have a good idea. It appears that timing of the signal is likely the key. It is also the case that the children with brainstem timing deficits are the ones who benefit the most from commercially available remediation programs. So if we can better identify these same children, we have a better chance to improve their auditory processing, and perhaps reading and spelling, too.

Beck: Nina, every time I speak with you I learn a lot! Thanks for your time.

Kraus: Thank you too, Doug. It's been a pleasure talking to you too.

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For more information ...

Auditory Neuroscience Lab Website: www.communication.northwestern.edu/brainvolts/

Auditory Neuroscience Lab Website: Clinical Technologies: www.communication.northwestern.edu/brainvolts/ClinicalTechnologies/

Auditory Neuroscience Lab Website: Publications: www.communication.northwestern.edu/brainvolts/list/

Bio-logic Systems: www.blsc.com/
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Nina Kraus, PhD



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