Auditory Cortical Images of Cochlear-Implant Stimuli: Dependence on Electrode Configuration
Kresge Hearing Research Institute (Department of Otorhinolaryngology) and Neuroscience Program, University of Michigan, Ann Arbor, Michigan 48109-0506 Bierer, Julie Arenberg and John C. Middlebrooks. Auditory Cortical Images of Cochlear-Implant Stimuli: Dependence on Electrode Configuration. J. Neur...
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Published in | Journal of neurophysiology Vol. 87; no. 1; pp. 478 - 492 |
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Main Authors | , |
Format | Journal Article |
Language | English |
Published |
United States
Am Phys Soc
01.01.2002
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Subjects | |
Online Access | Get full text |
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Summary: | Kresge Hearing Research Institute (Department of
Otorhinolaryngology) and Neuroscience Program, University of Michigan,
Ann Arbor, Michigan 48109-0506
Bierer, Julie Arenberg and
John C. Middlebrooks.
Auditory Cortical Images of Cochlear-Implant Stimuli: Dependence
on Electrode Configuration. J. Neurophysiol. 87: 478-492, 2002. This study examines patterns of
auditory cortical activity elicited by single-pulse cochlear implant
stimuli that vary in electrode configuration, cochlear place of
stimulation, and stimulus level. Recordings were made from the primary
auditory cortex (area A1) of ketamine-anesthetized guinea pigs. The
spatiotemporal pattern of neural spike activity was measured
simultaneously across 16 cortical locations spanning approximately 2-3
octaves of the tonotopic axis. Such a pattern, averaged over 40 presentations of any particular stimulus, was defined as the
"cortical image" of that stimulus. Acutely deafened guinea pigs
were implanted with a 6-electrode animal version of the 22-electrode
Nucleus banded electrode array (Cochlear). Cochlear electrode
configurations consisted of monopolar (MP), bipolar (BP + N )
with N inactive electrodes between the active and return
electrodes (0 N 4), tripolar (TP) with one active electrode and two flanking return electrodes, and common ground
(CG) with one active electrode and as many as five return electrodes.
Cortical images typically showed a focus of maximum spike probability
and minimum latency. Spike probabilities tended to decrease, and
latencies tended to increase, with increasing cortical distance from
that focus. Cortical images of TP stimuli were the most spatially
compact, followed by BP + N images, and then MP images,
which were the broadest. Images of CG stimuli were rather variable
across animals and stimulus channels. The locations of cortical images
shifted systematically from caudal to rostral as the cochlear place of
stimulation changed from basal to apical. At the most sensitive
cortical site for each condition, the dynamic ranges over which spike
rates increased with increased current level were restricted to about
1-2 dB, regardless of configuration. Dynamic ranges tended to increase
with increasing cortical distance from the most sensitive site.
Electrode configurations that produced compact cortical images (e.g.,
TP and BP + 0) showed the greatest range of thresholds within each
cortical image and the largest dynamic range at cortical sites removed
from the most sensitive site. |
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Bibliography: | ObjectType-Article-2 SourceType-Scholarly Journals-1 ObjectType-Feature-1 content type line 23 |
ISSN: | 0022-3077 1522-1598 |
DOI: | 10.1152/jn.00212.2001 |