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 email:
estrick@purdue.edu
(765) 494-3804
I have a background in psychology, audiology and neuroscience.
In my research I have people listen to carefully designed
tones and noises, and from their responses I come up
with theories about how the auditory system works.
I use stimuli that are very precisely controlled in
time and in frequency, such as tones and noises, because
the auditory system is so complex that it is only by
using very controlled stimuli that we can get a clear
picture of what is happening. Over the past few years
I have been working on a very exciting line of research
examining how the auditory system changes as it is stimulated
by sound. One example of this sort of change is the
fact that a brief tone that occurs at the onset of a
longer duration noise is harder to hear than one that
is delayed from the onset of the noise. This effect,
often called overshoot, has been attributed to effects
as peripheral as adaptation in the VIIIth nerve, and
as central as attention. In my research, I have found
strong evidence that overshoot actually results from
the auditory system turning down amplification in the
cochlea as it is stimulated by sound. This is a critically
important finding, because it explains a wealth of other
very basic psychophysical data in addition to the overshoot
effect. Also, it has been known for some time that
there is efferent feedback to the cochlea, which has
been shown to turn down cochlear amplification in anesthetized
animals, but it has been difficult to demonstrate its
effects behaviorally. The results of my research in
awake, behaving humans suggest that the efferent system
plays a key role in auditory perception. This also has
important clinical applications. In the past, we have
tended to compare normal and impaired hearing as if
the auditory system were static. My research suggests
that the normal auditory system is changing in a dynamic
manner in response to sound, while the impaired system
does not, and this could explain why hearing impairment
causes more difficulty than might be expected from a
simple elevation in hearing threshold.
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