Evidence against a predictive role for rhythm in speech perception.
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Biomedical subjects
Publications and source records attributed to L H Mens.
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Amplitude modulation following responses (AMFR) or steady-state evoked potentials (SSEPs) can be used for the objective and frequency-specific estimation of hearing thresholds in awake and sleeping subjects. To be useful as a clinical tool, a high signal to noise ratio (SNR) is required for a minimal testing time. Four EEG derivations were compared in six relaxed, cooperative awake normally hearing adults to compare the SNRs. Stimuli comprised a 1 kHz carrier wave, amplitude modulated at 39 Hz and 90 Hz. They were presented for about 4.4 min in one ear at a level slightly above the behavioural threshold (10 dB SL). In the 39 Hz condition, the SNRs from the different derivations did not differ significantly. However, in the 90 Hz condition one novel derivation (Cz-inion with ground at Pz) yielded a significantly lower noise level, about 60 per cent of the noise level of the other derivations. The SNR of this derivation was about 50 per cent larger than from other derivations. Such an increase of the SNR implies that testing time is reduced by about 56 per cent as compared to conventional derivations in these subjects.
Open set speech understanding with cochlear implants, without speechreading, is nowadays a common finding. However, there is a large variation in speech understanding between cochlear implant users. We tried to find pre-operative parameters which predicted the post-operative results. Thirty-seven adult post-lingually deafened Nucleus cochlear implant users with a mean age of 46 years (range 16 68) and a mean duration of deafness of 15 years (range 1.5-47) were studied. Pre-operatively, we performed pure-tone audiometry, round window and ear canal electrical stimulation, psychological tests and imaging. Additionally, we measured pre-operatively speech understanding in the auditory, the visual and the audiovisual conditions with several tests which were also administered after 6 and 12 months' implant experience. Correlation analysis between the pre-operative variables and the post-operative factors showed that duration of deafness and residual hearing are the most important predictors. The temporal difference limen in pre-operative round window electrical stimulation is a secondary predictor.