Faculty Bibliography

HYPOTHESES: Do cochlear implants provide enough information to allow adult cochlear implant users to understand words in ways that are similar to listeners with acoustic hearing? Can we use a computational model to gain insight into the underlying mechanisms used by cochlear implant users to recognize spoken words? BACKGROUND: The Neighborhood Activation Model has been shown to be a reasonable model of word recognition for listeners with normal hearing. The Neighborhood Activation Model assumes that words are recognized in relation to other similar-sounding words in a listener's lexicon. The probability of correctly identifying a word is based on the phoneme perception probabilities from a listener's closed-set consonant and vowel confusion matrices modified by the relative frequency of occurrence of the target word compared with similar-sounding words (neighbors). Common words with few similar-sounding neighbors are more likely to be selected as responses than less common words with many similar-sounding neighbors. Recent studies have shown that several of the assumptions of the Neighborhood Activation Model also hold true for cochlear implant users. METHODS: Closed-set consonant and vowel confusion matrices were obtained from 26 postlingually deafened adults who use cochlear implants. Confusion matrices were used to represent input errors to the Neighborhood Activation Model. Responses to the different stimuli were then generated by the Neighborhood Activation Model after incorporating the frequency of occurrence counts of the stimuli and their neighbors. Model outputs were compared with obtained performance measures on the Consonant-Vowel Nucleus-Consonant word test. Information transmission analysis was used to assess whether the Neighborhood Activation Model was able to successfully generate and predict word and individual phoneme recognition by cochlear implant users. RESULTS: The Neighborhood Activation Model predicted Consonant-Vowel Nucleus-Consonant test words at levels similar to those correctly identified by the cochlear implant users. The Neighborhood Activation Model also predicted phoneme feature information well. CONCLUSION: The results obtained suggest that the Neighborhood Activation Model provides a reasonable explanation of word recognition by postlingually deafened adults after cochlear implantation. It appears that multichannel cochlear implants give cochlear implant users access to their mental lexicons in a manner that is similar to listeners with acoustic hearing. The lexical properties of the test stimuli used to assess performance are important to spoken-word recognition and should be included in further models of the word recognition process

We report the results of our study of 25 children who underwent tonsillectomy and/or adenoidectomy under endotracheal general anesthesia with respect to their risk of fire in the oropharynx. We also attempt to explain the reasons for the difference between the relatively high incidence of airway explosions and fires that have occurred during tracheostomy with electrosurgery and electrocautery and the low incidence of these events during electrosurgical dissection of the tonsils. Finally, we review the precautions that physicians can take to lower the risk of operating-room fires and explosions

No widely accepted protocol or guideline exists for monitoring ototoxicity in patients who take powerful and potentially cochleotoxic and/or vestibulotoxic agents. Many physicians in other specialties who prescribe these drugs do not understand the important role of otolaryngologists and audiologists in pretreatment counseling and evaluation and the need for follow-up assessments of their patients' auditory function. Based on our combined experience of more than 50 years, we have developed a uniform yet flexible approach to monitoring cochlear and vestibular function in these patients. We discuss the mechanisms of ototoxic agents, risk factors for ototoxicity, the need for ongoing communication among the various disciplines, and the methods and timing of monitoring

We determined how the perceived naturalness of music and speech (male and female talkers) signals was affected by various forms of linear filtering, some of which were intended to mimic the spectral 'distortions' introduced by transducers such as microphones, loudspeakers, and earphones. The filters introduced spectral tilts and ripples of various types, variations in upper and lower cutoff frequency, and combinations of these. All of the differently filtered signals (168 conditions) were intermixed in random order within one block of trials. Levels were adjusted to give approximately equal loudness in all conditions. Listeners were required to judge the perceptual quality (naturalness) of the filtered signals on a scale from 1 to 10. For spectral ripples, perceived quality decreased with increasing ripple density up to 0.2 ripple/ERB(N) and with increasing ripple depth. Spectral tilts also degraded quality, and the effects were similar for positive and negative tilts. Ripples and/or tilts degraded quality more when they extended over a wide frequency range (87-6981 Hz) than when they extended over subranges. Low- and mid-frequency ranges were roughly equally important for music, but the mid-range was most important for speech. For music, the highest quality was obtained for the broadband signal (55-16,854 Hz). Increasing the lower cutoff frequency from 55 Hz resulted in a clear degradation of quality. There was also a distinct degradation as the upper cutoff frequency was decreased from 16,845 Hz. For speech, there was a marked degradation when the lower cutoff frequency was increased from 123 to 208 Hz and when the upper cutoff frequency was decreased from 10,869 Hz. Typical telephone bandwidth (313 to 3547 Hz) gave very poor quality

OBJECTIVE: Anomalies of the fourth branchial arch complex are exceedingly rare, with approximately forty cases reported in the literature since 1972. The authors report experience with six fourth arch anomalies. METHODS: Retrospective chart review of six consecutive patients presenting to the pediatric otolaryngology service at a tertiary care center with anomalies referable to the fourth branchial arch. RESULTS: All six patients presented within the first or second decade of life. All six had left-sided disease. Four patients presented with recurrent neck infection, one with asymptomatic cervical masses, and one with a neck mass and respiratory compromise. One patient had prior surgery presented with a recurrence. Diagnosis of fourth arch anomalies was suggested or confirmed by computed tomography and flexible laryngoscopy. Treatment was surgical in five patients; one patient is awaiting surgery. Surgical procedures included resection of the mass and endoscopic cauterization of the inner opening of the cyst. CONCLUSIONS: The presentation of a cervical mass, especially with recurrent infections and especially on the left side, in a child in the first or second decade of life heightens suspicion for an anomaly of the fourth branchial arch. Diagnosis can be difficult, but is aided by the use of flexible laryngoscopy, Computed tomography (CT) scanning and ultrasonography. Surgical resection of the cyst and cauterization of its pyriform sinus opening should be undertaken to minimize recurrence

BACKGROUND: Increasingly, deaf students are educated in mainstream school environments. This poses a question of how deaf children negotiate the demands of forming friendships with their hearing peers. The present study was designed to examine coping strategies of 35 deaf children attending full or partial mainstream school settings. METHOD: Using a qualitative analysis design, a range of coping strategies used by the children was described based on parents' reports. The relative success of these coping strategies in establishing relationships with hearing peers was assessed by examining strategies that increased the social success of deaf girls and boys. RESULTS: The results showed differences by gender in the effectiveness of coping strategies used by the participants. Deaf girls who were confident and frequently asked for clarifications or who were comfortable playing alone tended to achieve good relationships with hearing peers. In contrast, deaf boys' relationships with hearing peers benefited mostly from the boys' ability to perform well in sports. CONCLUSIONS: These findings are discussed in light of existing research on coping and current debates on the benefits of mainstreaming for deaf children

A group of central auditory neurons residing in the lateral superior olivary nucleus (LSO) responds selectively to interaural level differences and may contribute to sound localization. In this simple circuit, ipsilateral sound increases firing of LSO neurons, whereas contralateral sound inhibits the firing rate via activation of the medial nucleus of the trapezoid body (MNTB). During development, individual MNTB fibers arborize within the LSO, but they undergo a restriction of their boutons that ultimately leads to mature topography. A critical issue is whether a distinct form of inhibitory synaptic plasticity contributes to MNTB synapse elimination within LSO. Whole-cell recording from LSO neurons in brain slices from developing gerbils show robust long-term depression (LTD) of the MNTB-evoked IPSP/Cs when the MNTB was activated at a low frequency (1 Hz). These inhibitory synapses also display mixed GABA/glycinergic transmission during development, as assessed physiologically and immunohistochemically (Kotak et al. 1998). While either glycine or GABA(A) receptors could independently display inhibitory LTD, focal delivery of GABA, but not glycine, at the postsynaptic-locus induces depression. Furthermore, the GABA(B) receptor antagonist, SCH-50911, prevents GABA or synaptically induced depression. Preliminary evidence also indicated strengthening of inhibitory transmission (LTP) by a distinct pattern of inhibitory activity. These data support the idea that GABA is crucial for the expression inhibitory LTD and that this plasticity may underlie the early refinement of inhibitory synaptic connections in the LSO

Glycinergic transmission shapes the coding properties of the lateral superior olivary nucleus (LSO). We investigated intracellular pH responses in the LSO to glycine using BCECF-AM in brain slices. With extracellular bicarbonate, glycine produced an alkalinization followed by an acidification while, in the nominal absence of bicarbonate, glycine produced acidifications. Separately, in whole-cell recordings from LSO neurons, glycine caused hyperpolarization followed by long-lasting depolarization. While the bicarbonate-dependent intracellular alkalinization could be related to chloride/bicarbonate exchange, bicarbonate-independent acidification may be triggered by depolarization