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Speech perception in elderly patients following cochlear implantation.

CONCLUSIONS: Elderly patients benefit from cochlear implantation in terms of speech perception and quality of life. Age alone should be no contraindication for implantation. OBJECTIVE: There have been concerns whether elderly patients may perform poorly after cochlear implantation due to degenerative processes in the central and peripheral auditory systems. The purpose of this study was to analyze the benefits of cochlear implantation in elderly patients in comparison to younger recipients. MATERIAL AND METHODS: We examined 26 postlingually deafened adults aged > 65 years who received a cochlear implant at our center regarding preoperative findings, comorbidities, postoperative complications and quality of life. Speech perception was assessed by means of multi- and monosyllabic word recognition and compared to the results obtained by younger patients. RESULTS: The surgical procedure was well tolerated by all patients without notable perioperative complications. In terms of speech perception, no significant differences between the elderly patients and younger recipients were noted. All patients found that cochlear implantation had a positive impact on their quality of life.

Age Factors↗

Modulation of motor excitability during speech perception: the role of Broca's area.

Studies in both human and nonhuman primates indicate that motor and premotor cortical regions participate in auditory and visual perception of actions. Previous studies, using transcranial magnetic stimulation (TMS), showed that perceiving visual and auditory speech increased the excitability of the orofacial motor system during speech perception. Such studies, however, cannot tell us which brain regions mediate this effect. In this study, we used the technique of combining positron emission tomography with TMS to identify the brain regions that modulate the excitability of the motor system during speech perception. Our results show that during auditory speech perception, there is increased excitability of motor system underlying speech production and that this increase is significantly correlated with activity in the posterior part of the left inferior frontal gyrus (Broca's area). We propose that this area "primes" the motor system in response to heard speech even when no speech output is required and, as such, operates at the interface of perception and action.

Adult↗

A clinical test for the assessment of binaural speech perception in noise.

The present paper describes a clinical test for the assessment of speech perception in noise. The test was designed to separate the effects of several relevant monaural and binaural cues. Results show that the performance of individual hearing-impaired listeners deviates significantly from normal for at least 2 of the following aspects: (1) perception of speech in steady-state noise; (2) relative binaural advantage due to directional cues; (3) relative advantage due to masker fluctuations. In contrast, both the hearing loss for reverberated speech and the relative binaural advantage due to interaural signal decorrelation, caused by reverberation, were essentially normal for almost all hearing impaired.

Adult↗

Speech perception performance of nucleus multichannel cochlear implant users with partial electrode insertions.

OBJECTIVE: The present investigation examined the speech perception performance of five children with ossified cochleas who received partial insertions of the Nucleus 22-channel cochlear implant. DESIGN: The partial-insertion subjects' preimplant and 1.5 yr postimplant performance on a battery of speech perception tests was compared to the average performance of age-matched control subjects who received full electrode insertions. All the partial-insertion subjects were fit with their Nucleus cochlear implant between the ages of 2 and 5 yr, and had used their device for at least 1.5 yr. More extended comparisons also were made for the two partial-insertion subjects who had used their cochlear implants for a longer period of time. RESULTS: The subjects with partial electrode insertions performed similarly to the control group at both the preimplant and 1.5 yr postimplant intervals. Furthermore, the partial-insertion subjects showed continued improvements in speech perception performance with increased device experience past 1.5 yr, again similar to the full-insertion control group. CONCLUSIONS: The present results suggest that partial insertion of a multichannel implant device is an appropriate and feasible approach to the surgical management and auditory rehabilitation of children with extensive or complete ossification of the cochlea.

Child, Preschool↗

Auditory-visual speech perception and aging.

OBJECTIVE: This experiment was designed to assess the integration of auditory and visual information for speech perception in older adults. The integration of place and voicing information was assessed across modalities using the McGurk effect. The following questions were addressed: 1) Are older adults as successful as younger adults at integrating auditory and visual information for speech perception? 2) Is successful integration of this information related to lipreading performance? DESIGN: The performance of three groups of participants was compared: young adults with normal hearing and vision, older adults with normal to near-normal hearing and vision, and young controls, whose hearing thresholds were shifted with noise to match the older adults. Each participant completed a lipreading test and auditory and auditory-plus-visual identification of syllables with conflicting auditory and visual cues. RESULTS: The results show that on average older adults are as successful as young adults at integrating auditory and visual information for speech perception at the syllable level. The number of fused responses did not differ for the CV tokens across the ages tested. Although there were no significant differences between groups for integration at the syllable level, there were differences in the response alternatives chosen. Young adults with normal peripheral sensitivity often chose an auditory alternative whereas, older adults and control participants leaned toward visual alternatives. In additions, older adults demonstrated poorer lipreading performance than their younger counterparts. This was not related to successful integration of information at the syllable level. CONCLUSIONS: Based on the findings of this study, when auditory and visual integration of speech information fails to occur, producing a nonfused response, participants select an alternative response from the modality with the least ambiguous signal.

Acoustic Stimulation↗

Seeking the neurobiological bases of speech perception.

One of the most highly developed human abilities is communication by speech. Throughout the years, research on speech perception has demonstrated that humans are well adapted to extract highly encoded linguistic information from the speech signal. The sophisticated nature of these capacities and their early appearance during development suggest the existence of a rich biological substrate for speech perception. In the present paper, we describe some of these important capacities and examine research from different domains that may help illuminate the nature of their biological foundations.

Animals↗

Critique: articulatory-acoustic relations and their role in speech perception.

These remarks are in response to "Role of articulation in speech perception: Clues from production"ony Björn Lindblom. It is suggested that the form in which the lexicon is stored includes both segments and distinctive features, and this representation is neutral with respect to articulatory and the acoustic domains. The process by which features are determined from the sound requires that patterns of acoustic properties be identified. In developing models of speech perception, knowledge of articulatory-acoustic relations can be a guide in defining these properties, but it is not necessary for the models to assign primary status to articulation.

Humans↗

Contributions of temporal encodings of voicing, voicelessness, fundamental frequency, and amplitude variation to audio-visual and auditory speech perception.

Auditory and audio-visual speech perception was investigated using auditory signals of invariant spectral envelope that temporally encoded the presence of voiced and voiceless excitation, variations in amplitude envelope and F0. In experiment 1, the contribution of the timing of voicing was compared in consonant identification to the additional effects of variations in F0 and the amplitude of voiced speech. In audio-visual conditions only, amplitude variation slightly increased accuracy globally and for manner features. F0 variation slightly increased overall accuracy and manner perception in auditory and audio-visual conditions. Experiment 2 examined consonant information derived from the presence and amplitude variation of voiceless speech in addition to that from voicing, F0, and voiced speech amplitude. Binary indication of voiceless excitation improved accuracy overall and for voicing and manner. The amplitude variation of voiceless speech produced only a small increment in place of articulation scores. A final experiment examined audio-visual sentence perception using encodings of voiceless excitation and amplitude variation added to a signal representing voicing and F0. There was a contribution of amplitude variation to sentence perception, but not of voiceless excitation. The timing of voiced and voiceless excitation appears to be the major temporal cues to consonant identity.

Acoustic Stimulation↗

Responses of single units in the cat cochlear nucleus to sinusoidal amplitude modulation of tones and noise: linearity and relation to speech perception.

Responses to the sinusoidal modulation envelopes of amplitude-modulated tonend noise carriers were recorded from single units in the cochlear nucleus of the cat. The unit discharges were synchronized to the peaks of the modulation envelope. Population-averaged firing rate were independent of the modulation index of the stimulus. Temporal firing patterns, as represented by the shapes and magnitudes of modulation-cycle histograms, were strongly dependent on stimulus intesity and modulation index. Nonlinear nonsinusoidal responses to sinusoidal modulation envelopes were observed, but only at high values of sound intensity. These and other results are discussed in the context of psychological studies concerning the perception of speech information.

Acoustic Stimulation↗

Electrode discrimination and speech perception in young children using cochlear implants.

OBJECTIVE: The aim was to determine the efficacy of a child-appropriate procedure to assess electrode discrimination ability in young children using cochlear implants and to investigate the relationship of electrode discrimination ability and speech perception performance in children implanted at a young age. DESIGN: An adaptation of the play audiometry procedure was used to assess electrode discrimination in seventeen 4- to 10-yr-old children. The children were required to respond with a game-like motor response when a repeating stimulation on a reference electrode "changed" to a different electrode. They were also assessed on a speech feature discrimination test, a closed-set word recognition test and a nonverbal intelligence task. RESULTS: Sixty-five percent of subjects demonstrated ability to discriminate adjacent electrodes in mid and apical regions of the cochlea, whilst the remaining subjects needed electrode separations of between two and nine electrodes for successful discrimination. In a forward stepwise regression analysis electrode discrimination ability was found to be the strongest factor in accounting for variance in the speech perception scores. Subject variables such as duration of deafness, nonverbal intelligence and implant experience did not significantly account for further variance in the speech perception scores for this group of children. CONCLUSIONS: Electrode discrimination ability was the strongest factor in predicting performance on speech perception measures in a group of children using cochlear implants.

Child↗

Cochlear implantation in obstructed cochleas: the effect of the degree of obstruction on the number of activated electrodes and the amount of postoperative speech perception.

OBJECTIVE: With cochlear implantation, insertion of the electrodes can be hampered by cochlear obstructions. The aim of this study was to investigate the effects of these obstructions on the number of activated electrodes and postoperative speech perception. STUDY DESIGN AND SETTING: Retrospective analysis of the operation reports and CT-scans of patients who underwent cochlear implantation, at the Department of Otorhinolaryngology of the University Medical Center of Utrecht (n = 295). PATIENTS AND INTERVENTIONS: Fifty patients with a certain degree of cochlear obstruction were included. Based on the surgical intervention to overcome these obstructions they were subdivided into first-, second- and third degree obstructions. The number of implanted and activated electrodes was determined. MAIN OUTCOME MEASURES: Three different speech perception tests after 12 months of cochlear implant use. RESULTS: The number of activated electrodes significantly diminished with increasing obstruction degree (P < 0.01). This was caused by a lower amount of implanted electrodes combined with a higher amount of switched off electrodes. With a higher degree of obstruction the amount of postoperative speech perception decreased significantly (P < 0.01). This is partly explained by the lower number of activated electrodes and partly explained by the fact that a higher obstructions degree correlates with a higher degree of (retro-) cochlear pathology. Significantly more electrodes can be inserted into the severely obstructed cochlea using a Double Array Cochlear Implant. CONCLUSION: Cochlear obstructions pose a surgical threat and negatively influence the postoperative speech perception results. Fortunately, due to surgical techniques, first and second degree obstructed cochleas can often be bypassed. Implanting of a Double Array implant brightens the prospects of patients with third (severe) degree obstructed cochleas.

Audiometry, Speech↗

Speech perception in noise: directional microphones versus frequency modulation (FM) systems.

The major consequence of sensorineural hearing loss (SNHL) is communicative difficulty, especially with the addition of noise and/or reverberation. The purpose of this investigation was to compare two types of technologies that have been shown to improve the speech-perception performance of individuals with SNHL: directional microphones and frequency modulation (FM) systems. Forty-six adult subjects with slight to severe SNHL served as subjects. Speech perception was assessed using the Hearing in Noise Test (HINT) with correlated diffuse noise under five different listening conditions. Results revealed that speech perception was significantly better with the use of the FM system over that of any of the hearing aid conditions, even with the use of the directional microphone. Additionally, speech perception was significantly better with the use of two hearing aids used in conjunction with two FM receivers rather than with just one FM receiver. Directional microphone performance was significantly better than omnidirectional microphone performance. All aided listening conditions were significantly better than the unaided listening condition.

Adult↗

Auditory-visual speech perception in an adult with aphasia.

The evaluation of auditory-visual speech perception is not typically undertaken in the assessment of aphasia; however, treatment approaches utilise bimodal presentations. Research demonstrates that auditory and visual information are integrated for speech perception. The strongest evidence of this cross-modal integration is the McGurk effect. This indirect measure of integration shows that presentation of conflicting tokens may change perception (e.g. auditory /bi/ + visual /gi/ = /di/). The purpose of this study was to investigate the ability of a person with mild aphasia to identify tokens presented in auditory-only, visual-only and auditory-visual conditions. It was hypothesized that performance would be best in the bimodal condition and that presence of the McGurk effect would demonstrate integration of speech information. Findings did not support the hypotheses. It is suspected that successful integration of AV speech information was limited by a perseverative response pattern. This case study suggests the use of bisensory speech information may be impaired in adults with aphasia.

Acoustic Stimulation↗

Comparison of speech perception in background noise with acceptance of background noise in aided and unaided conditions.

Background noise is a significant factor influencing hearing-aid satisfaction and is a major reason for rejection of hearing aids. Attempts have been made by previous researchers to relate the use of hearing aids to speech perception in noise (SPIN), with an expectation of improved speech perception followed by an increased acceptance of hearing aids. Unfortunately, SPIN was not related to hearing-aid use or satisfaction. A new measure of listener reaction to background noise has been proposed. The acceptable noise level (ANL), expressed in decibels, is defined as a difference between the most comfortable listening level for speech and the highest background noise level that is acceptable when listening to and following a story. The ANL measure assumes that speech understanding in noise may not be as important as is the willingness to listen in the presence of noise. It has been established that people who accept background noise have smaller ANLs and tend to be "good" users of hearing aids. Conversely, people who cannot accept background noise have larger ANLs and may only use hearing aids occasionally or reject them altogether. Because this is a new measure, it was important to determine the reliability of the ANL over time with and without hearing aids, to determine the effect of acclimatization to hearing aids, and to compare the ANL to well-established measures such as speech perception scores collected with the SPIN test. Results from 50 listeners indicate that for both good and occasional hearing aid users, the ANL is comparable in reliability to the SPIN test and that both measures do not change with acclimatization. The ANLs and SPIN scores are unrelated. Although the SPIN scores improve with amplification, the ANLs are unaffected by amplification, suggesting that the ANL is inherent to an individual and can be established prior to hearing aid fitting as a possible predictor of hearing-aid use.

Adaptation, Physiological↗

Specialization of left auditory cortex for speech perception in man depends on temporal coding.

Speech perception requires cortical mechanisms capable of analysing and encoding successive spectral (frequency) changes in the acoustic signal. To study temporal speech processing in the human auditory cortex, we recorded intracerebral evoked potentials to syllables in right and left human auditory cortices including Heschl's gyrus (HG), planum temporale (PT) and the posterior part of superior temporal gyrus (area 22). Natural voiced /ba/, /da/, /ga/) and voiceless (/pa/, /ta/, /ka/) syllables, spoken by a native French speaker, were used to study the processing of a specific temporally based acoustico-phonetic feature, the voice onset time (VOT). This acoustic feature is present in nearly all languages, and it is the VOT that provides the basis for the perceptual distinction between voiced and voiceless consonants. The present results show a lateralized processing of acoustic elements of syllables. First, processing of voiced and voiceless syllables is distinct in the left, but not in the right HG and PT. Second, only the evoked potentials in the left HG, and to a lesser extent in PT, reflect a sequential processing of the different components of the syllables. Third, we show that this acoustic temporal processing is not limited to speech sounds but applies also to non-verbal sounds mimicking the temporal structure of the syllable. Fourth, there was no difference between responses to voiced and voiceless syllables in either left or right areas 22. Our data suggest that a single mechanism in the auditory cortex, involved in general (not only speech-specific) temporal processing, may underlie the further processing of verbal (and non-verbal) stimuli. This coding, bilaterally localized in auditory cortex in animals, takes place specifically in the left HG in man. A defect of this mechanism could account for hearing discrimination impairments associated with language disorders.

Acoustic Stimulation↗

Selective speech perception alterations in schizophrenic patients reporting hallucinated "voices".

OBJECTIVE: The authors tested a model of hallucinated "voices" based on a neural network computer simulation of disordered speech perception. METHOD: Twenty-four patients with schizophrenia spectrum disorders who reported hallucinated voices were compared with 21 patients with schizophrenia spectrum disorders who did not report voices and 26 normal subjects. Narrative speech perception was assessed through use of a masked speech tracking task with three levels of superimposed phonetic noise. A sentence repetition task was used to assess grammar-dependent verbal working memory, and an auditory continuous performance task was used to assess nonlanguage attention. RESULTS: Masked speech tracking task and sentence repetition performance by hallucinating patients was impaired relative to both nonhallucinating patients and normal subjects. Although both hallucinating and nonhallucinating patients demonstrated auditory attention impairments when compared to normal subjects, the two patient groups did not differ with respect to these variables. CONCLUSIONS: Results support the hypothesis that hallucinated voices in schizophrenia arise from disrupted speech perception and verbal working memory systems rather than from nonlanguage cognitive or attentional deficits.

Adult↗

Initial evaluation of the Clarion CII cochlear implant: speech perception and neural response imaging.

OBJECTIVE: To evaluate the new Clarion CII cochlear implant with the perimodiolar HiFocus electrode array, including both speech perception outcomes and the device's capabilities of measuring the electrically evoked compound action potential (eCAP) of the auditory nerve (Neural Response Imaging, NRI). DESIGN: The speech perception scores on CVC words without lip reading were monitored prospectively for the 10 postlingually deaf patients implanted with the Clarion CII device in the period July 2000 until May 2001 in the Leiden University Medical Center. Preoperative and postoperative NRI recordings were made, applying various combinations of monopolar stimulating and recording electrodes with the alternating polarity paradigm available in the test bench software. RESULTS: Nine patients preferred the CIS, one the PPS strategy, none the SAS strategy. With their favorite strategy they acquired significant open set speech understanding within a few weeks, resulting in an average CVC phoneme score of 84% (word score 66%) at the end of the study (follow-up 3 to 11 mo). In speech-shaped noise, the average phoneme recognition threshold (PRT) was reached at a signal to noise ratio just below 0 dB. The NRI recordings had clear N1 and P1 peaks if there was at least one contact between the stimulating and recording electrodes, necessitating just 15 sweeps for a reliable recording. We observed considerable inter-patient and inter-electrode variability, but for a given situation NRI input/output curves were stable over time. More apical contacts generally elicited larger eCAPs. Response amplitudes tended to peak at recording sites around apical and basal stimulating electrodes, suggesting a limited spread of excitation. Preliminary recordings with the forward masking paradigm were consistent with the ones with the alternating polarity scheme. CONCLUSIONS: The Clarion CII is a promising cochlear implant with which our first 10 patients have obtained excellent speech perception results. The NRI system yields high quality signals with a limited number of sweeps at a high sampling rate.

Acoustic Stimulation↗

Electrophysiological and speech perception measures of auditory processing in experienced adult cochlear implant users.

OBJECTIVE: This study determined the relationship between auditory evoked potential measures and speech perception in experienced adult cochlear implant (CI) users and compared the CI evoked potential results to those of a group of age- and sex-matched control subjects. METHODS: CI subjects all used the Nucleus CI-22 implant. Middle latency response (MLR), obligatory cortical potentials (CAEP), mismatch negativity (MMN) and P3a auditory evoked potentials were recorded. Speech perception was evaluated using word and sentence tests. RESULTS: Duration of deafness correlated with speech scores with poor scores reflecting greater years of deafness. Na amplitude correlated negatively with duration of deafness, with small amplitudes reflecting greater duration of deafness. Overall, N1 amplitude was smaller in CI than control subjects. Earlier P2 latencies were associated with shorter durations of deafness and higher speech scores. In general, MMN was absent or degraded in CI subjects with poor speech scores. CONCLUSIONS: Auditory evoked potentials are related to speech perception ability and provide objective evidence of central auditory processing differences across experienced CI users. SIGNIFICANCE: Since auditory evoked potentials relate to CI performance, they may be a useful tool for objectively evaluating the efficacy of speech processing strategies and/or auditory training approaches in both adults and children with cochlear implants.

Acoustic Stimulation↗