Rate and onset cues can improve cochlear implant synthetic vowel recognition in noise.
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ABSTRACT:
SUBMITTER: Mc Laughlin M
PROVIDER: S-EPMC3606303 | biostudies-other | 2013 Mar
REPOSITORIES: biostudies-other
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Project description:OBJECTIVES:The standard, monopolar (MP) electrode configuration used in commercially available cochlear implants (CI) creates a broad electrical field, which can lead to unwanted channel interactions. Use of more focused configurations, such as tripolar and phased array, has led to mixed results for improving speech understanding. The purpose of the present study was to assess the efficacy of a physiologically inspired configuration called dynamic focusing, using focused tripolar stimulation at low levels and less focused stimulation at high levels. Dynamic focusing may better mimic cochlear excitation patterns in normal acoustic hearing, while reducing the current levels necessary to achieve sufficient loudness at high levels. DESIGN:Twenty postlingually deafened adult CI users participated in the study. Speech perception was assessed in quiet and in a four-talker babble background noise. Speech stimuli were closed-set spondees in noise, and medial vowels at 50 and 60 dB SPL in quiet and in noise. The signal to noise ratio was adjusted individually such that performance was between 40 and 60% correct with the MP strategy. Subjects were fitted with three experimental strategies matched for pulse duration, pulse rate, filter settings, and loudness on a channel-by-channel basis. The strategies included 14 channels programmed in MP, fixed partial tripolar (? = 0.8), and dynamic partial tripolar (? at 0.8 at threshold and 0.5 at the most comfortable level). Fifteen minutes of listening experience was provided with each strategy before testing. Sound quality ratings were also obtained. RESULTS:Speech perception performance for vowel identification in quiet at 50 and 60 dB SPL and for spondees in noise was similar for the three tested strategies. However, performance on vowel identification in noise was significantly better for listeners using the dynamic focusing strategy. Sound quality ratings were similar for the three strategies. Some subjects obtained more benefit than others, with some individual differences explained by the relation between loudness growth and the rate of change from focused to broader stimulation. CONCLUSIONS:These initial results suggest that further exploration of dynamic focusing is warranted. Specifically, optimizing such strategies on an individual basis may lead to improvements in speech perception for more adult listeners and improve how CIs are tailored. Some listeners may also need a longer period of time to acclimate to a new program.
| S-EPMC6129442 | biostudies-literature
Project description:Cochlear implant patients have difficulty in noisy environments, in part, because of channel interaction. Interleaving the signal by sending every other channel to the opposite ear has the potential to reduce channel interaction by increasing the space between channels in each ear. Interleaving still potentially provides the same amount of spectral information when the two ears are combined. Although this method has been successful in other populations such as hearing aid users, interleaving with cochlear implant patients has not yielded consistent benefits. This may be because perceptual misalignment between the two ears, and the spacing between stimulation locations must be taken into account before interleaving.Eight bilateral cochlear implant users were tested. After perceptually aligning the two ears, 12-channel maps were made that spanned the entire aligned portions of the array. Interleaved maps were created by removing every other channel from each ear. Participants' spectral resolution and localization abilities were measured with perceptually aligned processing strategies both with and without interleaving.There was a significant improvement in spectral resolution with interleaving. However, there was no significant effect of interleaving on localization abilities.The results indicate that interleaving can improve cochlear implant users' spectral resolution. However, it may be necessary to perceptually align the two ears and/or use relatively large spacing between stimulation locations.
| S-EPMC4767634 | biostudies-literature
Project description:Normal-hearing (NH) listeners maintain robust speech understanding in modulated noise by "glimpsing" portions of speech from a partially masked waveform--a phenomenon known as masking release (MR). Cochlear implant (CI) users, however, generally lack such resiliency. In previous studies, temporal masking of speech by noise occurred randomly, obscuring to what degree MR is attributable to the temporal overlap of speech and masker. In the present study, masker conditions were constructed to either promote (+MR) or suppress (-MR) masking release by controlling the degree of temporal overlap. Sentence recognition was measured in 14 CI subjects and 22 young-adult NH subjects. Normal-hearing subjects showed large amounts of masking release in the +MR condition and a marked difference between +MR and -MR conditions. In contrast, CI subjects demonstrated less effect of MR overall, and some displayed modulation interference as reflected by poorer performance in modulated maskers. These results suggest that the poor performance of typical CI users in noise might be accounted for by factors that extend beyond peripheral masking, such as reduced segmental boundaries between syllables or words. Encouragingly, the best CI users tested here could take advantage of masker fluctuations to better segregate the speech from the background.
| S-EPMC3339508 | biostudies-other
Project description:Cochlear implant (CI) users are unable to receive masking release and the reasons are unclear. The present study examines the hypothesis that when listening to speech in fluctuating maskers, CI users cannot fuse the pieces of the message over temporal gaps because they are not able to perceive reliably the information carried by obstruent consonants (e.g., stops). To test this hypothesis, CI users were presented with sentences containing clean obstruent segments, but corrupted sonorant segments (e.g., vowels). Results indicated that CI users received masking release at low signal-to-noise ratio levels. Experiment 2 assessed the contribution of acoustic landmarks alone by presenting to CI users noise-corrupted stimuli which had clearly marked vowel/consonant boundaries, but lacking clean obstruent consonant information. These stimuli were created using noise-corrupted envelopes processed using logarithmic compression during sonorant segments and a weakly-compressive mapping function during obstruent segments. Results indicated that the use of segment-dependent compression yielded significant improvements in intelligibility, but no masking release. The results from these experiments suggest that in order for CI users to receive masking release, it is necessary to perceive reliably not only the presence and location of acoustic landmarks (i.e., vowel/consonant boundaries) but also the information carried by obstruent consonants.
| S-EPMC2945752 | biostudies-other
Project description:Cochlear implant users hear pitch evoked by stimulation rate, but discrimination diminishes for rates above 300 Hz. This upper limit on rate pitch is surprising given the remarkable and specialized ability of the auditory nerve to respond synchronously to stimulation rates at least as high as 3 kHz and arguably as high as 10 kHz. Sensitivity to stimulation rate as a pitch cue varies widely across cochlear implant users and can be improved with training. The present study examines individual differences and perceptual learning of stimulation rate as a cue for pitch ranking. Adult cochlear implant users participated in electrode psychophysics that involved testing once per week for three weeks. Stimulation pulse rate discrimination was measured in bipolar and monopolar configurations for apical and basal electrodes. Base stimulation rates between 100 and 800 Hz were examined. Individual differences were quantified using psychophysically derived metrics of spatial tuning and temporal integration. This study examined distribution of measures across subjects, predictive power of psychophysically derived metrics of spatial tuning and temporal integration, and the effect of training on rate discrimination thresholds. Psychophysical metrics of spatial tuning and temporal integration were not predictive of stimulation rate discrimination, but discrimination thresholds improved at lower frequencies with training. Since most clinical devices do not use variable stimulation rates, it is unknown to what extent recipients may learn to use stimulation rate cues if provided in a clear and consistent manner.
| S-EPMC7714175 | biostudies-literature
Project description:Sequential stream segregation involves the ability of a listener to perceptually segregate two rapidly alternating sounds into different perceptual streams. By studying auditory streaming in cochlear implants (CIs), one can obtain a better understanding of the cues that CI recipients can use to segregate different sound sources, which may have relevance to such everyday activities as the understanding of speech in background noise. This study focuses on the ability of CI users to use temporal periodicity cues to perform auditory stream segregation. A rhythmic discrimination task involving sequences of alternating amplitude-modulated (AM) noises is used. The results suggest that most CI users can stream AM noise bursts at relatively low modulation frequencies (near 80 Hz AM), but that this ability diminishes at higher modulation frequencies. Additionally, the ability of CI users to perform streaming using temporal periodicity cues appears to be comparable to that of normal-hearing listeners. These results imply that CI subjects may in certain contexts (i.e., when the talker has a low fundamental frequency voice) be able to use temporal periodicity cues to segregate and thus understand the voices of competing talkers.
| S-EPMC2723898 | biostudies-other
Project description:ObjectivesPrevious studies investigating speech perception in noise have typically been conducted with static masker positions. The aim of this study was to investigate the effect of spatial separation of source and masker (spatial release from masking, SRM) in a moving masker setup and to evaluate the impact of adaptive beamforming in comparison with fixed directional microphones in cochlear implant (CI) users.DesignSpeech reception thresholds (SRT) were measured in S0N0 and in a moving masker setup (S0Nmove) in 12 normal hearing participants and 14 CI users (7 subjects bilateral, 7 bimodal with a hearing aid in the contralateral ear). Speech processor settings were a moderately directional microphone, a fixed beamformer, or an adaptive beamformer. The moving noise source was generated by means of wave field synthesis and was smoothly moved in a shape of a half-circle from one ear to the contralateral ear. Noise was presented in either of two conditions: continuous or modulated.ResultsSRTs in the S0Nmove setup were significantly improved compared to the S0N0 setup for both the normal hearing control group and the bilateral group in continuous noise, and for the control group in modulated noise. There was no effect of subject group. A significant effect of directional sensitivity was found in the S0Nmove setup. In the bilateral group, the adaptive beamformer achieved lower SRTs than the fixed beamformer setting. Adaptive beamforming improved SRT in both CI user groups substantially by about 3 dB (bimodal group) and 8 dB (bilateral group) depending on masker type.ConclusionsCI users showed SRM that was comparable to normal hearing subjects. In listening situations of everyday life with spatial separation of source and masker, directional microphones significantly improved speech perception with individual improvements of up to 15 dB SNR. Users of bilateral speech processors with both directional microphones obtained the highest benefit.
| S-EPMC4430230 | biostudies-literature
Project description:OBJECTIVE:To determine whether patient-derived programming of one's cochlear implant (CI) stimulation levels may affect performance outcomes. BACKGROUND:Increases in patient population, device complexity, outcome expectations, and clinician responsibility have demonstrated the necessity for improved clinical efficiency. METHODS:Eighteen postlingually deafened adult CI recipients (mean?=?53 years; range, 24-83 years) participated in a repeated-measures, within-participant study designed to compare their baseline listening program to an experimental program they created. RESULTS:No significant group differences in aided sound-field thresholds, monosyllabic word recognition, speech understanding in quiet, speech understanding in noise, nor spectral modulation detection (SMD) were observed (p?>?0.05). Four ears (17%) improved with the experimental program for speech presented at 45?dB SPL and two ears (9%) performed worse. Six ears (27.3%) improved significantly with the self-fit program at +10?dB signal-to-noise ratio (SNR) and four ears (26.6%) improved in speech understanding at +5?dB SNR. No individual scored significantly worse when speech was presented in quiet at 60?dB SPL or in any of the noise conditions tested. All but one participant opted to keep at least one of the self-fitting programs at the completion of this study. Participants viewed the process of creating their program more favorably (t?=?2.11, p?=?0.012) and thought creating the program was easier than the traditional fitting methodology (t?=?2.12, p?=?0.003). Average time to create the self-fit program was 10?minutes, 10?seconds (mean?=?9:22; range, 4:46-24:40). CONCLUSIONS:Allowing experienced adult CI recipients to set their own stimulation levels without clinical guidance is not detrimental to success.
| S-EPMC5302051 | biostudies-literature
Project description:Word recognition is a gateway to language, linking sound to meaning. Prior work has characterized its cognitive mechanisms as a form of competition between similar-sounding words. However, it has not identified dimensions along which this competition varies across people. We sought to identify these dimensions in a population of cochlear implant users with heterogenous backgrounds and audiological profiles, and in a lifespan sample of people without hearing loss. Our study characterizes the process of lexical competition using the Visual World Paradigm. A principal component analysis reveals that people's ability to resolve lexical competition varies along three dimensions that mirror prior small-scale studies. These dimensions capture the degree to which lexical access is delayed ("Wait-and-See"), the degree to which competition fully resolves ("Sustained-Activation"), and the overall rate of activation. Each dimension is predicted by a different auditory skills and demographic factors (onset of deafness, age, cochlear implant experience). Moreover, each dimension predicts outcomes (speech perception in quiet and noise, subjective listening success) over and above auditory fidelity. Higher degrees of Wait-and-See and Sustained-Activation predict poorer outcomes. These results suggest the mechanisms of word recognition vary along a few underlying dimensions which help explain variable performance among listeners encountering auditory challenge.
| S-EPMC11362525 | biostudies-literature
Project description:The upper limit of rate-based pitch perception and rate discrimination can differ substantially across cochlear implant (CI) users. One potential reason for this difference is the presence of a biological limitation on temporal encoding in the electrically-stimulated auditory pathway, which can be inherent to the electrical stimulation itself and/or to the degenerative processes associated with hearing loss. Electrophysiological measures, like the electrically-evoked frequency following response (eFFR) and auditory change complex (eACC), could potentially provide valuable insights in the temporal processing limitations at the level of the brainstem and cortex in the electrically-stimulated auditory pathway. Obtaining these neural responses, free from stimulation artifacts, is challenging, especially when the neural response is phase-locked to the stimulation rate, as is the case for the eFFR. In this study we investigated the feasibility of measuring eFFRs, free from stimulation artifacts, to stimulation rates ranging from 94 to 196 pulses per second (pps) and eACCs to pulse rate changes ranging from 36 to 108%, when stimulating in a monopolar configuration. A high-sampling rate EEG system was used to measure the electrophysiological responses in five CI users, and linear interpolation was applied to remove the stimulation artifacts from the EEG. With this approach, we were able to measure eFFRs for pulse rates up to 162 pps and eACCs to the different rate changes. Our results show that it is feasible to measure electrophysiological responses, free from stimulation artifacts, that could potentially be used as neural correlates for rate and pitch processing in CI users.
| S-EPMC8052190 | biostudies-literature