Growth-function of electrically evoked brainstem responses in cochlear implant patients
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1
Klinikum rechts der Isar, HNO-Klinik, Germany
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2
Technische Universität München, Electrical Engineering and Information Technology, Germany
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3
University of Applied Science, Germany
This investigation develops a system for the objective measurement of auditory brain stem responses in awake cochlear implant patients. Electrical stimuli were delivered with MED-EL implants under computer control (via the RIB II interface) and responses were amplified with a biosignal amplifier (g.tec) and sampled synchronously with an A/D data acquisition board using custom software. Data analysis was conducted both on-line (to follow the measurement progress) and off-line to implement more complex stimulation- and muscle artifact rejection algorithms. In addition to the eBERA measurements, our patients also evaluated the perceived loudness of the pulse-trains used in these measurements.
Electrical stimulation artifacts were two orders of magnitude larger than wave V of the evoked potentials. They were removed using stimulation pulses with alternating polarity, discarding the initial part of the response (0.5 ms) and by fitting and subtracting the remaining artifact with an exponentially decaying function. We then could analyze the responses easier, identify wave V at high stimulation levels and track it by eye down to low levels. An objective threshold criterion was established based on the binomial average. For low to medium stimulation amplitudes the amplitude of wave V amplitude grew linearly with the perceived loudness, individual correlation coefficients were between 0.81 and 1. Notably, our measurements were very sensitive, the objective detection threshold was between the loudness categories “soft” and “very soft” (Würzburger Hörfeld).
In summary our results indicate that carefully measured and analyzed eBERA data provides interesting insights into loudness growth in CIs. If a systematic relation between single-pulse thresholds and burst stimulation can be established, it can be even used for objective threshold estimations.
Acknowledgements
Supported by the Bernstein Center for Computational Neuroscience Munich (01GQ1004B) and a grant from MED-EL.
Keywords:
Cochlear Implants,
eBERA,
electrically evoked potentials,
loudness scaling
Conference:
Bernstein Conference 2012, Munich, Germany, 12 Sep - 14 Sep, 2012.
Presentation Type:
Poster
Topic:
Neurotechnology and brain-machine interface
Citation:
Steinhoff
H,
Lackner
C,
Giesse
C,
Chong
X,
Nicoletti
M,
Giebel
A and
Hemmert
W
(2012). Growth-function of electrically evoked brainstem responses in cochlear implant patients.
Front. Comput. Neurosci.
Conference Abstract:
Bernstein Conference 2012.
doi: 10.3389/conf.fncom.2012.55.00082
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Received:
22 May 2012;
Published Online:
12 Sep 2012.
*
Correspondence:
Prof. Werner Hemmert, Technische Universität München, Electrical Engineering and Information Technology, Garching, 85748, Germany, werner.hemmert@tum.de