University of Iowa Department of Communication Sciences

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University of Iowa Department of Communication
Sciences Disorders

• Audiology

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Human Electrophysiology Lab

• Carolyn Brown, PhD
• Professor

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Human Electrophysiology Lab

• Paul Abbas, PhD
• Professor

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Electrically evoked compound action potential
(ECAP)

• A neural potential
• Synchronous firing of a large number of auditory
  nerve fibers in response to an electrical
  stimulus.
• Negative peak (N1) with a latency of 0.2 to 0.5
  ms
• Positive peak or a plateau (P2) follows.
• The spatial spread of neural excitation is
  assessed by measuring the amount of channel
  interaction using a forward masking paradigm.

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Assessment of channel interaction using
Subtraction Method
base
apex
Response to MASKER and PROBE
Masker-probe Interval .5 ms
Response to PROBE
Subtraction Method Response
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Assessment of channel interaction with
forward-masking
using subtraction recorded method implemented
with Nucleus NRT
apex
base
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Binaural interaction EABR

• The binaural interaction component (BIC) is the
  difference between the algebraic sum of the two
  monaural evoked potentials (L/R) and the evoked
  potential recorded in response to simultaneous
  binaural stimulation.
• Neural generator Inhibitory-Excitatory units in
  the lateral superior olive complex (LSO).
• The BIC of the EABR has been recorded from adult
  and pediatric bilateral users
• (Pelizzone et al., 1990 Firszt et al., 2005
  Gordon et al., 2007)

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Effect of electrode pairing on the BIC of the EABR

• Subjects
• 7 bilateral, adult Nucleus CI users
• Electrode pairs
• 11 total
• Right ear fixed electrode 12
• Left ear varied electrodes 6 to 18
• Stimuli delivery
• Nucleus Implant Communication (NIC) routines
• Specially modified, Laura (L34) speech processors
• Stimulus levels
• Loudness balanced levels

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BIC Right ear electrode 12
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Electrically evoked cortical change complex (ECC)

• N1-P2 complex evoked by changes in stimulus
  parameters.
• May reflect more than detection (discrimination).
  
• Can be recorded from adult as well as pediatric
  CI users.

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Change Stimulating Electrode

• Stimulus 1000 Hz biphasic pulse train (25
  us/phase)
• 300-400 ms on one electrode
• 300-400 ms on a second electrode
• Recorded EEG using a contralateral electrode
  montage
• Averaged 300 sweeps
• Filtered out stimulus artifact (1-100 Hz).

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Individual data 5 electrode separation

• N 10 postlingually deafened adult CI users
• 4-5 electrode change between first and second
  half of the recording interval
• Both at stimulus bursts same current level and
  within a few CUs of C-level.

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Change Stimulating Electrode

• Electrically evoked change potentials
• Stimulus artifact filters out.
• Morphology and peak latencies similar to onset
  response.
• Reflects sensitivity to change in place of
  stimulation within the cochlea.

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Change Modulate pulse amplitude

• 1000 ms stimulus burst.
• Systematically vary the amplitude of pulses in a
  200 ms interval at the center of the burst.
• Approximates amplitude modulation

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Amplitude Growth with Increased Modulation Depth
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Hearing Lab

• Christopher Turner, Ph.D.
• Professor

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Short Electrode for severe high-frequency hearing
loss
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Iowa/Nucleus HybridClinical Trial II

• Inclusion Criteria
• gt15 years old
• Implant ear
• 10-60 CNC
• Ipsilateral ear
• Up to 80 CNC

Trial II
Original Hybrid Trial
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Speech recognition for10 mm electrode patient
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Increase in perceptionof place feature
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Familiar Melody Recognition
Hybrid SE significantly more accurate than LE
or HiRes (plt.0004)
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Auditory Research Lab

• Shawn Goodman, PhD
• Assistant Professor

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Research involving Otoacoustic Emissions (OAEs)

• Mechanisms of OAE production How do they change
  as a function of stimulus type and level?
• OAE adaptation How are OAEs modified by
  efferent activation?

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Research involving hearing aids

• What signal processing paradigms can be used to
  quantify the electro-acoustic characteristics of
  modern hearing aids?
• How can such paradigms be designed to have
  perceptual validity?

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Facilities

• Etymotic Research ER-10B and ER-10C for OAE
  measurement
• Lynx L22 sound card, custom software for stimulus
  delivery recording

• 9' X 8' double-walled sound booth.
• KEMAR acoustics research mannequin

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Publications

• Measurement of Hearing Aid Internal Noise Using
  Synchronous Averaging
• Poster Presentation at American Auditory Society
• March 2008

http//www.uiowa.edu/comsci/research/arl/ARLhome.
html
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Hearing Aid LabBasic Applied Research

• Ruth Bentler, PhD
• Professor

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Evaluating Technologies

• Efficacy
• Does the technology do what it is designed to do.
• Effectiveness
• Does the technology provide benefit to the user.

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Evaluating Technologies

• Directional Microphones
• Why do results in the lab differ from results in
  the field?
• Digital Noise Reduction
• How does it work across manufacturers and does it
  improve speech perception in noise?

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Listeners select Omnidirectional over Directional
when

• The internal noise is audible (and it is)
• Visual cues are available

NO audible mic noise
Audible mic Noise
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DNR Speech
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DNR Speech White Noise
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DNR affects word recognition

• Significantly better speech recognition
  performance at better SNRs
• Speech recognition significantly better with
  DNR-on (!)
• DNR-max significantly better that DNR-default
• Unaltered (unprocessed) always best

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