Magdalene Ortmann

Cognitive resources related to speech recognition with a competing talker in young and older listeners

Speech recognition in a multi-talker situation poses high demands on attentional and other central resources. This study examines the relationship between age, cognition and speech recognition in tasks that require selective or divided attention in a multi-talker setting. Two groups of normal-hearing adults (one younger and one older group) were asked to repeat utterances from either one or two concurrent speakers. Cognitive abilities were then inspected by neuropsychological tests. Speech recognition scores approached its ceiling and did not significantly differ between age groups for tasks that demanded selective attention. However, when divided attention was required, performance in older listeners was reduced as compared to the younger group. When selective attention was required, speech recognition was strongly related to working memory skills, as determined by a regression model. In comparison, speech recognition for tests requiring divided attention could be more strongly determined by neuropsychological probes of fluid intelligence. The findings of this study indicate that - apart from hearing impairment - cognitive aspects account for the typical difficulties of older listeners in a multi-speaker setting. Our results are discussed in the context of evidence showing that frontal lobe functions in terms of working memory and fluid intelligence generally decline with age.

Neural Correlates of Speech Processing in Prelingually Deafened Children and Adolescents with Cochlear Implants

Prelingually deafened children with cochlear implants stand a good chance of developing satisfactory speech performance. Nevertheless, their eventual language performance is highly variable and not fully explainable by the duration of deafness and hearing experience. In this study, two groups of cochlear implant users (CI groups) with very good basic hearing abilities but non-overlapping speech performance (very good or very bad speech performance) were matched according to hearing age and age at implantation. We assessed whether these CI groups differed with regard to their phoneme discrimination ability and auditory sensory memory capacity, as suggested by earlier studies. These functions were measured behaviorally and with the Mismatch Negativity (MMN). Phoneme discrimination ability was comparable in the CI group of good performers and matched healthy controls, which were both better than the bad performers. Source analyses revealed larger MMN activity (155–225 ms) in good than in bad performers, which was generated in the frontal cortex and positively correlated with measures of working memory. For the bad performers, this was followed by an increased activation of left temporal regions from 225 to 250 ms with a focus on the auditory cortex. These results indicate that the two CI groups developed different auditory speech processing strategies and stress the role of phonological functions of auditory sensory memory and the prefrontal cortex in positively developing speech perception and production.

Effects of Hearing Loss and Cognitive Load on Speech Recognition with Competing Talkers

Everyday communication frequently comprises situations with more than one talker speaking at a time. These situations are challenging since they pose high attentional and memory demands placing cognitive load on the listener. Hearing impairment additionally exacerbates communication problems under these circumstances. We examined the effects of hearing loss and attention tasks on speech recognition with competing talkers in older adults with and without hearing impairment. We hypothesized that hearing loss would affect word identification, talker separation and word recall and that the difficulties experienced by the hearing impaired listeners would be especially pronounced in a task with high attentional and memory demands. Two listener groups closely matched for their age and neuropsychological profile but differing in hearing acuity were examined regarding their speech recognition with competing talkers in two different tasks. One task required repeating back words from one target talker (1TT) while ignoring the competing talker whereas the other required repeating back words from both talkers (2TT). The competing talkers differed with respect to their voice characteristics. Moreover, sentences either with low or high context were used in order to consider linguistic properties. Compared to their normal hearing peers, listeners with hearing loss revealed limited speech recognition in both tasks. Their difficulties were especially pronounced in the more demanding 2TT task. In order to shed light on the underlying mechanisms, different error sources, namely having misunderstood, confused, or omitted words were investigated. Misunderstanding and omitting words were more frequently observed in the hearing impaired than in the normal hearing listeners. In line with common speech perception models, it is suggested that these effects are related to impaired object formation and taxed working memory capacity (WMC). In a post-hoc analysis, the listeners were further separated with respect to their WMC. It appeared that higher capacity could be used in the sense of a compensatory mechanism with respect to the adverse effects of hearing loss, especially with low context speech.

Impact of coupling techniques of an active middle ear device to the round window membrane for the backward stimulation of the cochlea.

Hypothesis Interposed cartilage and the round window coupler (RWC) increase the efficiency of cochlea stimulation with the floating mass transducer (FMT) of a single active middle ear implant (AMEI) placed against the round window membrane. Background Treatment of mixed and conductive hearing loss with an AMEI attached to the round window is effective, yet the best placement technique of its FMT for the most efficient stimulation of the cochlea remains to be determined. Methods Experimental study on human temporal bones with the FMT placed against firstly the unaltered round window niche and then subsequently against the fully exposed round window membrane with and without interposed cartilage and the RWC. Cochlea stimulation is measured by the volume velocities of the stapes footplate using LASER vibrometry. Results At the undrilled round window niche, placement of the FMT by itself and with the RWC resulted in similar volume velocities. The response was significantly raised by interposing cartilage into the undrilled round window niche. Complete exposure of the round window membrane allowed for significantly increased volume velocities. Among these, coupling of the FMT with interposed cartilage yielded responses of similar magnitude compared with the RWC but significantly higher compared with the FMT by itself. Conclusion Good contact to the round window membrane is essential for efficient stimulation of the cochlea. Therefore, interposing cartilage into the undrilled round window niche is a viable option. At the drilled round window membrane, the FMT with interposed cartilage and attached to the RWC are similarly effective.

Loads and Coupling Modalities Influence the Performance of the Floating Mass Transducer as a Round Window Driver.

Hypothesis: High loads forcing the floating mass transducer (FMT) of a single active middle ear implant toward the round window membrane (RWM) affect the backward stimulation of the cochlea. Background: Various factors influence the backward stimulation of the cochlea. We investigated the effects of various loads applied to the FMT together with different coupling techniques at the fully exposed RWM on the vibration transmission. Methods: Experimental study on temporal bones with the FMT linked to a load cell mounted on a translation stage moving it against the fully exposed RWM with increasing loads up to 200 mN by itself, with interposed perichondrium, cartilage or connected to the round window coupler. Cochlear stimulation is measured by the volume velocities of the stapes footplate using LASER-Doppler-vibrometry. Results: Loads ranging from 5 to 20 mN induce the highest volume velocities of the stapes footplate. Increasing loads decrease the transmission of vibration in the low-frequency range but enhance the transmission of high frequencies. The interposition of perichondrium and cartilage proved to be advantageous. Conclusion: The load applied to the FMT distinctly affects the backward stimulation of the cochlea. Although increasing loads have inverse effects on the transmission of low and high frequencies, high loads lead to an overall decrease of cochlear stimulation. Out of the applied coupling techniques interposed perichondrium and cartilage allow for the most efficient stimulation.

Surgical Treatment for Early Stage Glottic Carcinoma with Involvement of the Anterior Commissure

Objective Assessment of the value of transoral laser microsurgery (TLM) compared with open surgery (OS) for early stage squamous cell carcinoma of the glottic larynx with special regard to involvement of the anterior commissure (AC). Study Design Case series with chart review. Setting Tertiary care otolaryngology clinic. Subjects and Methods Review of clinicopathological data of all patients with previously untreated T1a, T1b, and T2 glottic squamous cell carcinoma of the larynx who were consecutively enrolled over a 10-year period (January 1, 1992, to December 31, 2002). Results Local recurrence rate was 20.4% (10 of 49) for TLM and 10.7% (3 of 28) for OS. Comparison of the TLM and OS groups regarding local recurrence rates revealed a significant difference only for tumors invading the AC (P = .046). Within the TLM group, tumors with involvement of the AC showed a significantly higher recurrence rate (38.1%; 8 of 21) compared with tumors without involvement of the AC (7.1%; 2 of 28; P = .008). In the OS group, involvement of the AC revealed no significant difference (P = .45). The overall survival in both groups was comparable in both groups (TLM, 93.9%; OS, 89.3%; P = .47). Conclusion TLM and OS are equally effective surgical treatments for early stage glottic cancer without involvement of the AC, with selection of treatment based on pretreatment endoscopy. However, TLM is associated with less morbidity. In case of invasion of the AC, OS yields lower recurrence rates.

When Hearing Is Tricky: Speech Processing Strategies in Prelingually Deafened Children and Adolescents with Cochlear Implants Having Good and Poor Speech Performance

Cochlear implants provide individuals who are deaf with access to speech. Although substantial advancements have been made by novel technologies, there still is high variability in language development during childhood, depending on adaptation and neural plasticity. These factors have often been investigated in the auditory domain, with the mismatch negativity as an index for sensory and phonological processing. Several studies have demonstrated that the MMN is an electrophysiological correlate for hearing improvement with cochlear implants. In this study, two groups of cochlear implant users, both with very good basic hearing abilities but with non-overlapping speech performance (very good or very poor speech performance), were matched according to device experience and age at implantation. We tested the perception of phonemes in the context of specific other phonemes from which they were very hard to discriminate (e.g., the vowels in /bu/ vs. /bo/). The most difficult pair was individually determined for each participant. Using behavioral measures, both cochlear implants groups performed worse than matched controls, and the good performers performed better than the poor performers. Cochlear implant groups and controls did not differ during time intervals typically used for the mismatch negativity, but earlier: source analyses revealed increased activity in the region of the right supramarginal gyrus (220–260 ms) in good performers. Poor performers showed increased activity in the left occipital cortex (220–290 ms), which may be an index for cross-modal perception. The time course and the neural generators differ from data from our earlier studies, in which the same phonemes were assessed in an easy-to-discriminate context. The results demonstrate that the groups used different language processing strategies, depending on the success of language development and the particular language context. Overall, our data emphasize the role of neural plasticity and use of adaptive strategies for successful language development with cochlear implants.

Influence of Backside Loading on the Floating Mass Transducer: an in vitro experimental study

The vibration of the floating mass transducer (FMT) of a single active middle‐ear implant (AMEI) is distinctly influenced by the properties of the material coupled to its back side.

Acoustic effects of the reconstructed lateral epitympanic wall in a temporal bone and clinical study

Acoustic evaluation of reconstruction of the lateral epitympanic wall with bone or cartilage in a temporal bone study, and evaluation of audiometric data of patients who underwent cholesteatoma surgery with reconstruction of the lateral epitympanic wall with horseshoe‐shaped cartilage.

The Impact of a Cochlear Implant Electrode Array on the Middle Ear Transfer Function

Objectives: As a treatment for partial deafness with residual hearing in the lower frequency range, the combined acoustic and electric stimulation of the cochlea has become widespread. Acoustic stimulation is provided by a hearing aid’s airborne sound and the electric stimulation by a cochlear implant electrode array, which may be inserted through the round window or a cochleostomy. To take advantage of that concept, it is essential to preserve residual hearing after surgery. Therefore, the intracochlear electrode array should not compromise the middle ear vibration transmission. This study investigates the influence of different electrode types and insertion paths on the middle ear transfer function and the inner ear fluid dynamics. Design: Sound-induced oval and round window net volume velocities were calculated from vibration measurements with laser vibrometers on six nonfixated human temporal bones. After baseline measurements in the “natural” condition, a cochleostomy was drilled and closed with connective tissue. Then, four different electrode arrays were inserted through the cochleostomy. Afterwards, they were inserted through the round window while the cochleostomy was patched again with connective tissue. Results: After having drilled a cochleostomy and electrode insertion, no systematic trends in the changes of oval and round window volume velocities were observed. Nearly all changes of middle ear transfer functions, as well as oval and round window volume velocity ratios, were statistically insignificant. Conclusions: Intracochlear electrode arrays do not significantly increase cochlear input impedance immediately after insertion. Any changes that may occur seem to be independent of electrode array type and insertion path.