Biomedical subjects

Ekkehard Stürzebecher

Publications and source records attributed to Ekkehard Stürzebecher.

5 recordsLinked to original sources

PubMed2006

Objective detection of auditory steady-state responses: comparison of one-sample and q-sample tests.

Auditory steady-state responses (ASSR) are expected to be useful for the objective, frequency-specific assessment of hearing thresholds in small children. To detect ASSR close to the hearing threshold, a powerful statistical test has to be applied. At present, so-called one-sample tests are used. These tests only evaluate the phase, or the phase and amplitude, of the first harmonic, that is, the fundamental frequency. It is shown that higher harmonics with significant amplitudes are also contained in the ASSR spectrum. For this reason, statistical tests that only consider the first harmonic ignore a significant portion of the available information. The use of a q-sample test, which, in addition to the fundamental frequency, also includes higher harmonics in the detection leads to a better detection performance. The evaluation of test performance uses both detection rate and detection time.

Acoustic Stimulation↗

PubMed2006

New efficient stimuli for evoking frequency-specific auditory steady-state responses.

ASSR is a promising tool for the objective frequency-specific assessment of hearing thresholds in children. The stimulus generally used for ASSR recording (single amplitude-modulated carrier) only activates a small area on the basilar membrane. Therefore, the response amplitude is low. A stimulus with a broader frequency spectrum can be composed by adding several cosines whose frequency intervals comply with the desired stimulus repetition rate. Compensation of the travelling wave delay on the basilar membrane is possible with a stimulus of this type. Through this, a better synchronization of the neural response can be obtained and, as a result, higher response amplitudes can be expected, particularly for low-frequency stimuli. The additional introduction of a frequency offset enables the use of a q-sample test for the response detection, especially important at 500 Hz. The results of investigations carried out on a large group of normally hearing test subjects have confirmed the efficiency of this stimulus design. The new stimuli lead to significantly improved ASSRs with higher SNRs and thus higher detection rates and shorter detection times.

Acoustic Stimulation↗

PubMed2005

Combined electric and acoustic stimulation of the auditory system: results of a clinical study.

Combined electric and acoustic stimulation (EAS) of the auditory system is a new therapy for patients with severe to profound high- and mid-frequency hearing loss but remaining low-frequency hearing. In a prospective study, 13 patients with low-frequency hearing of better than 60 dB below 1 kHz were implanted with a MED-EL COMBI 40+ cochlear implant. Pure tone thresholds as well as monosyllabic word scores and Hochmair-Schulz-Moser sentences in quiet and in noise were measured with hearing aids, cochlear implant alone and in the combined stimulation mode (EAS) in the same ear. Hearing could be partially preserved in 11 out of the 13 patients. All patients scored significantly higher with cochlear implant alone than with hearing aids. Seven patients scored higher in the EAS mode than with cochlear implant alone for sentences in noise, 4 remained unchanged, and 2 could not use EAS. Synergistic effects of EAS were most prominent for hearing in noise with increases of up to 72% as compared to cochlear implant alone.

Acoustic Stimulation↗

PubMed2005

Automated auditory response detection: statistical problems with repeated testing.

Sequential application of a statistical test is usually applied in an automated auditory response detection algorithm. The sequential test strategy is very time-efficient but increases the probability of a false rejection of the null-hypothesis. For this reason, it is necessary to correct the critical test value. However, the well-known Bonferroni correction leads to an over-correction when dealing with dependent or partly dependent data. The objective of the study reported here was to develop a method to determine the critical test value for the sequential testing of dependent data. Extensive Monte Carlo simulations were used to develop this method. The simulation results were reviewed and the benefit of the suggested method, in comparison to the Bonferroni correction, was shown using a large sample of real amplitude modulation following response data. The detection rate determined for these data and the ROC curve demonstrate the advantage of using the method suggested here.

Algorithms↗

PubMed2003

Click-evoked ABR at high stimulus repetition rates for neonatal hearing screening.

A new, fast screening algorithm based on auditory brainstem response (ABR) recorded at a high click repetition rate is proposed. Response detection is carried out in the frequency domain by a statistical test procedure which includes the fundamental frequency and the harmonics below 800 Hz. First, the method was tested in 25 young adults. ABRs were recorded in the repetition rate range 20/s to 400/s. With a mean response detection time of 31 s, a click repetition rate of 140/s was found to be the optimum rate among the adult group. The method was then tested using a group of 114 neonates in whom the repetition rate range 60/s to 200/s was examined. At the repetition rate 90/s, which was found to be the optimum rate in neonates, the mean detection time was 24.6 s. In addition to the fast ABR detection, the proposed screening algorithm also allows simultaneous hearing screening of both ears using a one-channel data recording.

Acoustic Stimulation↗