Modulation detection thresholds for cochlear implants: Dependence on stimulation site and stimulus level

Purpose The goal was to evaluate the potential effects of increasing hearing loss and advancing age on spectral envelope perception. Method Spectral modulation detection was measured as a function of spectral modulation frequency from 0.5 to 8.0 cycles/octave. The spectral modulation task involved discrimination of a noise carrier (3 octaves wide from 400 to 3200 Hz) with a flat spectral envelope from a noise having a sinusoidal spectral envelope across a logarithmic audio frequency scale. Spectral modulation transfer functions (SMTFs; modulation threshold vs. modulation frequency) were computed and compared 4 listener groups: young normal hearing, older normal hearing, older with mild hearing loss, and older with moderate hearing loss. Estimates of the internal spectral contrast were obtained by computing excitation patterns. Results SMTFs for young listeners with normal hearing were bandpass with a minimum modulation detection threshold at 2 cycles/octave, and older listeners with normal hearing were remarkably similar to those of the young listeners. SMTFs for older listeners with mild and moderate hearing loss had a low-pass rather than a bandpass shape. Excitation patterns revealed that limited spectral resolution dictated modulation detection thresholds at high but not low spectral modulation frequencies. Even when factoring out (presumed) differences in frequency resolution among groups, the spectral envelope perception was worse for the group with moderate hearing loss than the other 3 groups. Conclusions The spectral envelope perception as measured by spectral modulation detection thresholds is compromised by hearing loss at higher spectral modulation frequencies, consistent with predictions of reduced spectral resolution known to accompany sensorineural hearing loss. Spectral envelope perception is not negatively impacted by advancing age at any spectral modulation frequency between 0.5 and 8.0 cycles/octave.

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Temporal Modulation Detection in Children and Adults With Cochlear Implants

Otology & Neurotology ◽

10.1097/mao.0000000000002122 ◽

2019 ◽

Vol 40 (3) ◽

pp. e311-e315 ◽

Cited By ~ 1

Author(s):

David Mark Landsberger ◽

Natalia Stupak ◽

Janet Green ◽

Kaitlyn Tona ◽

Monica Padilla ◽

...

Keyword(s):

Cochlear Implants ◽

Temporal Modulation ◽

Modulation Detection

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Effect of current focusing on the sensitivity of inferior colliculus neurons to amplitude-modulated stimulation

Journal of Neurophysiology ◽

10.1152/jn.00126.2016 ◽

2016 ◽

Vol 116 (3) ◽

pp. 1104-1116 ◽

Cited By ~ 3

Author(s):

Shefin S. George ◽

Mohit N. Shivdasani ◽

James B. Fallon

Keyword(s):

Inferior Colliculus ◽

Cochlear Implants ◽

Modulation Depth ◽

Neural Activation ◽

Detection Thresholds ◽

P Values ◽

Pulse Trains ◽

Spectral Cues ◽

Current Focusing ◽

Channel Interactions

In multichannel cochlear implants (CIs), current is delivered to specific electrodes along the cochlea in the form of amplitude-modulated pulse trains, to convey temporal and spectral cues. Our previous studies have shown that focused multipolar (FMP) and tripolar (TP) stimulation produce more restricted neural activation and reduced channel interactions in the inferior colliculus (IC) compared with traditional monopolar (MP) stimulation, suggesting that focusing of stimulation could produce better transmission of spectral information. The present study explored the capability of IC neurons to detect modulated CI stimulation with FMP and TP stimulation compared with MP stimulation. The study examined multiunit responses of IC neurons in acutely deafened guinea pigs by systematically varying the stimulation configuration, modulation depth, and stimulation level. Stimuli were sinusoidal amplitude-modulated pulse trains (carrier rate of 120 pulses/s). Modulation sensitivity was quantified by measuring modulation detection thresholds (MDTs), defined as the lowest modulation depth required to differentiate the response of a modulated stimulus from an unmodulated one. Whereas MP stimulation showed significantly lower MDTs than FMP and TP stimulation ( P values <0.05) at stimulation ≤2 dB above threshold, all stimulation configurations were found to have similar modulation sensitivities at 4 dB above threshold. There was no difference found in modulation sensitivity between FMP and TP stimulation. The present study demonstrates that current focusing techniques such as FMP and TP can adequately convey amplitude modulation and are comparable to MP stimulation, especially at higher stimulation levels, although there may be some trade-off between spectral and temporal fidelity with current focusing stimulation.

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