Research: Universitätsklinikum ErlangenUniversitätsklinikum Erlangen · Bereich für AudiologieGermany · Erlangen
Research: Universität des SaarlandesUniversität des Saarlandes · Klinik für Hals-, Nasen- und OhrenheilkundeGermany · Homburg
Research: Friedrich-Alexander Universität Erlangen-NürnbergFriedrich-Alexander Universität Erlangen-NürnbergGermany · Erlangen
Article: Melody identification for cochlear implant users and normal hearers using expanded pitch contours.[show abstract] [hide abstract]
ABSTRACT: Music perception is considered unsatisfactory for most cochlear implant (CI) users. Usually, rhythm identification is adequate while pitch and melody recognition are rather limited. The aim of this study was to investigate whether insufficient contour information in the low-frequency range is one cause that contributes to the poor melody recognition results in CI users. For this purpose, the recognition of familiar melodies was tested with three differently expanded pitch contours. Ten cochlear implant subjects and five normal-hearing (NH) volunteers were investigated. Each subject chose ten out of a possible set of 23 well-known nursery songs without verbal cues. The songs were played in the original version and with three different pitch-contour expansions. All versions were tested with and without rhythm and in random order. CI subjects exhibited best results when melodies were presented with expanded pitch contours, although no clear preference for a specific contour modification was observed. Normal-hearing subjects exhibited poorer results for expanded pitch contours, especially when testing without rhythm. Both NH and CI-user groups exhibited large inter-individual differences, and melody recognition with rhythm was always better than melody recognition without rhythm. Insufficient contour information in the low-frequency range is confirmed as one contributing cause for the poor melody recognition results in CI users. Therefore, other efforts to improve low-frequency pitch discrimination, e.g., a more sophisticated design of the electrode array, a focus of the electrical stimulation pattern or an improved signal processing scheme could potentially improve melody recognition as well.Archives of Oto-Rhino-Laryngology 12/2011; 269(11):2317-26. · 1.29 Impact Factor
Article: Effects of consonant-vowel transitions in speech stimuli on cortical auditory evoked potentials in adults.[show abstract] [hide abstract]
ABSTRACT: We examined the neural activation to consonant-vowel transitions by cortical auditory evoked potentials (AEPs). The aim was to show whether cortical response patterns to speech stimuli contain components due to one of the temporal features, the voice-onset time (VOT). In seven normal-hearing adults, the cortical responses to four different monosyllabic words were opposed to the cortical responses to noise stimuli with the same temporal envelope as the speech stimuli. Significant hemispheric asymmetries were found for speech but not in noise evoked potentials. The difference signals between the AEPs to speech and corresponding noise stimuli revealed a significant negative component, which correlated with the VOT. The hemispheric asymmetries can be referred to rapid spectral changes. The correlation with the VOT indicates that the significant component in the difference signal reflects the perception of the acoustic change within the consonant-vowel transition. Thus, at the level of automatic processing, the characteristics of speech evoked potentials appear to be determined primarily by temporal aspects of the eliciting stimuli.The Open Neurology Journal 01/2011; 5:37-45.
Article: Acoustic change complex in cochlear implant subjects in comparison with psychoacoustic measures.Cochlear implants international 01/2010; 11 Suppl 1:426-30.
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ABSTRACT: This study examined the role of central auditory completion in speech understanding. The perception of periodically interrupted speech was investigated. For this purpose, gaps were inserted into speech signals by silencing out defined intervals. The main hypothesis was that word recognition increases with shorter gaps and is less influenced by the total amount of gaps. Seventeen normal-hearing young adults took part in this study. Phrases from the German HSM speech recognition test were used as speech material. The examination comprised 220 modulated sentences presented binaurally at 65 dB. Intervals with durations ranging from 50 to 700 ms were taken to silence out 50, 65 and 80% of each sentence, respectively. Mean speech perception values were in the range of 65-92%, 35-92% and 35-95% correct answers for gap ratios of 50, 65 and 80%, respectively. When comparing the same interval duration, word recognition was better for smaller gap ratios. Both, gap ratio and gap duration had a significant influence on identification performance. Speech can be understood even when very large proportions are blanked out. A significant decrease in perception can be observed when gap duration exceeds more than half of the syllable length.Folia Phoniatrica et Logopaedica 09/2009; 61(5):263-8. · 1.12 Impact Factor
Article: Contribution of spectrotemporal features on auditory event-related potentials elicited by consonant-vowel syllables.[show abstract] [hide abstract]
ABSTRACT: To determine the influence of spectrotemporal properties of naturally produced consonant-vowel syllables to speech-evoked auditory event-related potentials (ERPs) for stimuli with very similar or even identical wide-band envelopes. Speech-evoked ERPs may be useful for validating the neural representation of speech. Speech-evoked ERPs were obtained from 10 normal-hearing young adults in response to the syllables /da/ and /ta/. Both monosyllables were obtained from ongoing speech. They have quite similar wide-band envelopes, and they mainly differ in the spectrotemporal content of the consonant parts. Additionally, each stimulus derivatives were investigated with (1) isolated consonant part ("consonant stimulus"), (2) isolated vowel part ("vowel stimulus"), and (3) removed spectral information but identical wide-band envelope. Latencies and amplitudes of the N1 and P2 components were determined and analyzed. ERPs in response to the naturally produced /ta/ syllable had significant shorter N1 and P2 latencies and larger amplitudes than ERPs in response to /da/. Similar differences were observed for the ERPs evoked by the consonant stimuli alone. For the vowel stimuli and stimuli with removed spectral information, no significant differences were observed. In summary, differences between the ERPs of /da/ and /ta/ corresponded to the distinct spectrotemporal content in the consonant parts of the original consonant-vowel (CV) syllables. The study shows that even small differences in spectrotemporal features of speech may evoke different ERPs, despite very similar or even identical wide-band envelopes. The results are consistent with a model that ERPs evoked by short CVs are an onset response to the consonant merged with an acoustic change complex evoked by the vowel part. However, all components appear as one P1-N1-P2 complex. The results may be explained by differences in the narrow-band envelopes of the stimuli. Therefore, this study underlines the limitations of the wide-band envelope in explaining speech-evoked ERPs. Additionally, the results of this study are of special interest for clinical application since some of the ERP parameter differences, as the N1 latency, are present not only in the ERPs of each single subject but also in the group mean value of all N1 latencies. Thus, presented ERP measurements in response to CVs might be used for identification of potential problems in phoneme differentiation caused by spectrotemporal analysis problems.Ear and hearing 09/2009; 30(6):704-12. · 2.06 Impact Factor