Comodulation Masking Release In Electric Hearing

Comodulation masking release (CMR) is an improvement in the detection threshold of a masked signal that occurs when the masker envelopes are correlated across frequency (i.e., comodulation). CMR can be observed when flanking bands (FBs) of noise co-modulated with an on-frequency band (OFB) noise mas...

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Bibliographic Details
Published inJournal of the Association for Research in Otolaryngology Vol. 15; no. 2; pp. 279 - 291
Main Authors Pierzycki, Robert H., Seeber, Bernhard U.
Format Journal Article
LanguageEnglish
Published Boston Springer US 01.04.2014
Springer Nature B.V
Subjects
Acoustic Stimulation
Aged
Auditory Threshold
Cochlear Implants
Electric Stimulation
Electrodes
Humans
Medicine
Medicine & Public Health
Middle Aged
Neurobiology
Neurosciences
Noise
Otorhinolaryngology
Perceptual Masking
Research Article
electrical stimulation
signal detection
envelope
cochlear implant
temporal processing
temporal fine structure
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Summary:Comodulation masking release (CMR) is an improvement in the detection threshold of a masked signal that occurs when the masker envelopes are correlated across frequency (i.e., comodulation). CMR can be observed when flanking bands (FBs) of noise co-modulated with an on-frequency band (OFB) noise masker are added at remote frequencies (CMR1), or when co-modulated envelopes are used instead of anti-modulated envelopes (OFB and FB envelopes out of phase, CMR2). For FBs widely separated from the OFB, this process is assumed to rely mostly on across-channel comparison of temporal envelopes. Since cochlear implants (CIs) rely predominantly on the transmission of envelope cues, we investigated if CMR can be observed in electric hearing. We stimulated the auditory nerve of eight CI users with trains of modulated electric pulses presented on an OFB electrode alone, or together with pulse trains on one or two FB electrodes. Participants had to detect signal-induced changes in the envelope of an electric pulse train masker presented on the OFB electrode. Envelopes on FB electrodes were either co-modulated or anti-modulated with the envelope of the OFB masker. We observed CMR1 in one of the eight CI users. However, significant CMR2 was observed in most CI users. Reducing amplitude-modulation rate from 20 to 8 Hz, reducing envelopes' randomness or increasing electrode separation did not generally improve CMR1, but increased the prevalence of CMR2. The present results suggest that comodulation of envelopes can aid signal detection in electric hearing.
ISSN:1525-3961
1438-7573
DOI:10.1007/s10162-013-0433-9