Biomedical subjects

Robert S Hong

Publications and source records attributed to Robert S Hong.

4 recordsLinked to original sources

PubMed2006

Conditioning pulse trains in cochlear implants: effects on loudness growth.

HYPOTHESIS: The addition of a high-rate (5 kpps) conditioning pulse train to the input signal of cochlear implants will result in shallower loudness growth across the dynamic range of cochlear implant patients. BACKGROUND: High-rate conditioning pulse trains have been shown to increase the dynamic range of sinusoidal stimuli for cochlear implant recipients in a manner consistent with stochastic resonance. This study further characterizes the effects of conditioning stimuli on loudness by examining the loudness growth functions for sinusoidal stimuli both with and without conditioning. METHODS: Seven post-lingually deafened adults using the Clarion CII cochlear implant participated in this study. The loudness growth functions of each subject were characterized using sinusoidal stimuli, both with and without the presence of a high-rate conditioner. Loudness was measured using magnitude estimation. RESULTS: The loudness growth functions of all seven subjects demonstrate an increase in dynamic range for sinusoidal stimuli with the addition of the conditioning pulse train. Shallower loudness growth is seen across the dynamic range with the addition of a conditioner. This result was shown for loudness growth fitted to exponential, power, and cumulative gaussian functions. CONCLUSION: The addition of high-rate conditioning pulse trains to sinusoidal stimuli presented to cochlear implant recipients results in larger dynamic ranges, with more gradual increases in loudness growth across the dynamic range. This suggests that signal-processing strategies incorporating conditioning may be clinically useful, requiring less compression of the input signal and leading to less distortion perceived by cochlear implant patients.

Adult↗

PubMed2006

Pure-tone auditory stream segregation and speech perception in noise in cochlear implant recipients.

This study examined the ability of cochlear implant users and normal-hearing subjects to perform auditory stream segregation of pure tones. An adaptive, rhythmic discrimination task was used to assess stream segregation as a function of frequency separation of the tones. The results for normal-hearing subjects were consistent with previously published observations (L.P.A.S van Noorden, Ph.D. dissertation, Eindhoven University of Technology, Eindhoven, The Netherlands 1975), suggesting that auditory stream segregation increases with increasing frequency separation. For cochlear implant users, there appeared to be a range of pure-tone streaming abilities, with some subjects demonstrating streaming comparable to that of normal-hearing individuals, and others possessing much poorer streaming abilities. The variability in pure-tone streaming of cochlear implant users was correlated with speech perception in both steady-state noise and multi-talker babble. Moderate, statistically significant correlations between streaming and both measures of speech perception in noise were observed, with better stream segregation associated with better understanding of speech in noise. These results suggest that auditory stream segregation is a contributing factor in the ability to understand speech in background noise. The inability of some cochlear implant users to perform stream segregation may therefore contribute to their difficulties in noise backgrounds.

Adult↗

PubMed2003

Dynamic range enhancement for cochlear implants.

HYPOTHESIS: The addition of a continuous, unmodulated, high-rate pulse train to sinusoidal stimuli presented by the cochlear implant to implant recipients will result in increases in the psychophysical dynamic range. BACKGROUND: The hearing dynamic range of cochlear implant patients is markedly reduced compared with that of normal-hearing individuals. This has negative implications for both speech perception and sound quality in these patients. It has been suggested that the addition of an unmodulated high-rate pulse train to deafened auditory nerves could create spontaneous-like neural activity, similar to that recorded from normal ears, of which one significant benefit would be an increase in the dynamic range of cochlear implant users. METHODS: Twenty-nine patients who underwent implantation with the Clarion CII device participated in this single-blinded prospective study. The psychophysical dynamic range of 28 of these subjects was measured with sinusoidal stimuli in response to various levels of an additional unmodulated high-rate pulse train. RESULTS: All the tested subjects (n = 28) demonstrated an increase in dynamic range in response to an appropriate level of unmodulated high-rate pulse train. The largest increase in dynamic range for each subject had a mean value of 6.7 dB. CONCLUSION: The addition of an unmodulated high-rate pulse train to the electric signal presented to cochlear implant patients results in significant increases in dynamic range for sinusoidal stimuli.

Acoustic Stimulation↗

PubMed2003

High-rate conditioning pulse trains in cochlear implants: dynamic range measures with sinusoidal stimuli.

The addition of a continuous, unmodulated, high-rate pulse train to the electrical signals of cochlear implant recipients results in statistically significant increases in psychophysical dynamic range (41 out of 46 electrode pairs tested). The observed increases in dynamic range are thought to result from nerve conditioning by appropriate levels of high-rate pulse train. Five dynamic range profiles are characterized, defining the different responses of dynamic range observed with increasing levels of the conditioner. Four of the five profiles demonstrate increases in dynamic range, with three showing behavior consistent with stochastic resonance. One profile depicts evidence of adaptation in response to higher levels of the conditioner, with a recovery period lasting throughout the duration (on the scale of tens of minutes) of experimentation. Dynamic range profiles are shown to be similar across sinusoidal frequencies (202, 515, and 1031 Hz) but potentially different across electrode pairs (electrodes 1-2, 7-8, and 15-16). Correlation analysis does not reveal any predictors of optimal conditioner level or amount of dynamic range increase with the conditioner.

Adult↗