Faculty Bibliography

OBJECTIVE: To reconcile conflicting reports concerning the incidence of otorrhea in children with tympanostomy tubes who swim without ear protection. STUDY SELECTION: Articles were identified by MEDLINE search, Current Contents, and references from review articles, textbook chapters, and retrieved reports. Controlled trials of water precautions following tympanostomy tube placement were selected by independent observers and scored on 10 measures of study validity. Five English-language articles met all inclusion criteria. DATA EXTRACTION: Data were abstracted for an endpoint of otorrhea following swimming without ear protection with a minimum follow-up of 6 weeks. DATA SYNTHESIS: Pooled analysis of 619 children revealed a rate difference of -5.04 (95% confidence interval [CI], -11.62 to 1.54). No significant difference in the incidence of otorrhea was noted between patients who swam without ear protection and nonswimmers. CONCLUSION: There is no increase in incidence of otorrhea in children who swim without ear protection compared with children who do not swim following tympanostomy tube placement

Inferior colliculus (IC) slice cultures from postnatal (P) day 6-8 gerbils exhibit axonal regeneration across a lesion site, and these regrowing processes can form synapses. To determine whether regenerative capacity is lost in older tissue, as occurs in vivo, slices from P12-21-day animals were grown under similar conditions. While these cultures displayed a near complete loss of neurons over 6 days in vitro, glutamate receptor antagonists (AP5 and/or CNQX) significantly enhanced survival, particularly at P12-15. In contrast, several growth factors or high potassium did not improve neuron survival. Therefore, axonal regeneration was assessed following complete transection of the commissure in AP5/CNQX-treated IC cultures from P12 animals. Neurofilament staining revealed that transected commissural axons survived for 6 days in vitro, but only a few processes crossed the lesion site and these axons did not extend into the contralateral lobe. In contrast, there was robust axonal sprouting and growth within one lobe of the IC, remote from the lesion site. When P6 and P12 tissue was explanted onto a coated substrate, the P6 axons grew onto the substrate, but the P12 axons were seemingly prevented from reaching the substrate by a veil of nonneuronal cells. Coculture of the IC and one of its afferent populations, the lateral superior olive, provided a similar finding, indicating that failure to regenerate was a general property at the age examined. These data show that neuron survival is not sufficient to permit axon regeneration at P12, and suggest that P12 lesion sites manufacture a prohibitive substrate since process outgrowth is blocked specifically at the commissure transection

The lateral superior olive (LSO) is a primary site of binaural convergence that responds selectively to changes in interaural level difference (ILD) by integrating ipsilateral excitatory and contralateral inhibitory inputs. The circuit matures during the first three postnatal weeks, undergoing several structural and functional changes that are influenced by afferent activity. Therefore modulation of synaptic activity by neuromodulators may participate in the maturation of this circuit. The present study describes robust effects of serotonin (5-HT) on LSO synaptic function. Using whole cell voltage-clamp recording from gerbil LSO neurons (postnatal days 6-13) in an in vitro slice preparation, we have identified several distinct forms of serotonergic modulation of spontaneous and evoked synaptic transmission. First, 1-2 min application of 5-HT (100 microM) activated prolonged bursts of spontaneous inhibitory postsynaptic currents (IPSCs). However, there was an age-dependent decline, such that this effect rarely was observed beyond postnatal day 8. 5-HT apparently increased the excitability of inhibitory afferents, because 5-HT-induced IPSCs were blocked by tetrodotoxin. A second effect of 5-HT was to depress rapidly and profoundly the amplitude of electrically evoked excitatory postsynaptic currents (EPSCs). In contrast, 5-HT also depressed evoked IPSCs but to a significantly lesser degree. The receptor subtypes mediating these effects were examined using specific 5-HT agonists and antagonists. A 5-HT1 agonist, 5-carboxamidotryptamine, produced EPSC depression but did not induce spontaneous IPSCs. A 5-HT2 agonist, alpha-Me-5-HT, reproduced all the observed effects of 5-HT (PSC depression as well as induction of spontaneous IPSCs), whereas a 5-HT2 antagonist, ketanserin, blocked the induction of spontaneous IPSCs. Therefore induction of spontaneous IPSCs is mediated by 5-HT2 receptors, whereas both 5-HT1 and 5-HT2 receptor types contribute to PSC depression. Serotonergic modulation of LSO synapses may have consequences for both developmental plasticity and auditory function. Serotonergic induction of IPSCs was observed primarily in young animals and thus may represent a mechanism for amplifying the activity of inhibitory synapses in LSO during a period of use-dependent plasticity in postnatal development. PSC depression, which preferentially affects excitation, is a potential mechanism for modulation of ILD tuning

Neural responses in the adult central auditory system to binaural stimuli can be altered by preceding acoustic events, including auditory motion. To determine whether the juvenile auditory system also exhibits this feature, we have examined interaural level difference (ILD) processing in the developing gerbil. A long binaural stimulus was followed without interruption by modulation of the level difference (virtual acoustic motion), which in turn was followed smoothly by a new steady state ILD. Auditory responses of single neurons in the inferior colliculus (IC) were assessed for sensitivity to the final steady state ILD. The response of EI neurons (excited by contralateral stimulation and inhibited ipsilaterally) was examined at postnatal (P) days 17-18, P24-25, and in adult animals. In adult animals, a sudden reduction of the inhibitory stimulus level resulted in a long-lasting (median = 4.3 s) enhanced discharge rate (conditioned enhancement). In P17-18 animals, conditioned enhancement only lasted for 1.2 s. When the inhibitory stimulus level was suddenly increased, adult neurons often displayed a conditioned suppression of discharge rate (median = 4.5 s), whereas P17-18 neurons remained suppressed for a much briefer period (median = 1.2 s). Moreover, the difference between conditioned responses and control discharge rates was three-four times greater in adult neurons compared to those recorded in P17-25 animals. Because conditioned responses are sensitive to the relative balance of contralateral excitation and ipsilateral inhibition, we examined the relationship between excitatory and inhibitory thresholds. In adult animals, excitatory thresholds were an average of 12 dB lower than inhibitory thresholds, while at P17-25 excitatory and inhibitory thresholds were roughly the same. These results indicate that computational properties of juvenile and adult IC neurons differ quantitatively, and this may reflect an imbalance between excitation and inhibition. The developmental differences described herein may limit the ability of young animals to locate a sound source with the latency and accuracy of an adult

The effects of mechanical compression on the multiple quantum coherences generated from sodium ions in articular cartilage were investigated. Cartilage samples obtained from bovine patellae were studied during compression at 0.7 MPa (100 psi) for 1 hour. The double quantum filtered spectra showed marked lineshape changes in the compressed samples. Compression did not seem to influence the lineshapes of the single quantum and triple quantum filtered spectra significantly. We found that the residual quadrupolar interaction was reduced in the compressed samples. Changes in the ordering of collagen fibers may be responsible for the observed effect.

OBJECTIVE:The purpose of this cadaver dissection study was to investigate the anatomy of the nasolabial fold with a view to explaining the problems of surgical softening or elimination of the fold. STUDY DESIGN/METHODS:Ten formalin-fixed cadavers and 6 fresh-frozen cadavers were used for this study. In 12 cadavers (8 formalin-fixed, 4 fresh-frozen), the nasolabial fold was sectioned at right angles to the fold for histologic examination, and in 4 cadavers (2 formalin-fixed, 2 fresh-frozen) the epithelium was dissected off the fold to allow for more detailed gross examination of the underlying musculature. RESULTS:The fold was clearly identified on 14 of the cadavers but was indistinct on 2 on gross examination. Beneath the fold were 2 muscle bundles. The more superficial muscle runs parallel to the fold whereas a deeper muscle runs at right angles to it. The buccal fat pad lies above the fold and appears to be retained by horizontal septae in the fat pad and also by the musculature of the fold. Cadavers showing a poorly defined nasolabial fold had fewer muscle bundles to support the fat and fewer fibrous septae running through the fat. CONCLUSIONS:The nasolabial fold is defined by structures that support the buccal fat pad and hold it above the fold. This appears to be a combination of muscle bundles that run both across and parallel to the fold and also by fibrous septae supporting the fat pad. This has implications for the development of surgical procedures to soften or eliminate the fold, which must separate the muscles from the dermis of the fold and allow the fat to descend and soften the fold.

OBJECTIVE:The present investigation examined the speech perception skills of pediatric cochlear implant users who changed from their original speech processors and strategies to the Spectral Peak (SPEAK) strategy. DESIGN/METHODS:A within-subjects design was used to compare individual subject's performance using the SPEAK strategy with that obtained with their previous speech strategy (FOF1F2 or Multipeak) in this retrospective study. The subjects demonstrated a wide range of perceptual abilities and had used a cochlear implant for varying lengths of time before converting to the SPEAK strategy. RESULTS:Nine of the 11 subjects showed significant improvement on at least one of the open-set word recognition measures, whereas two subjects showed no change on any of the open-set measures when using the SPEAK strategy. CONCLUSIONS:The present results suggest that the majority of pediatric cochlear implant users are likely to show improved speech perception performance when converting to the new SPEAK processing strategy.

OBJECTIVE:To examine changes over time in consonant feature production by children with profound hearing impairments who used either the Nucleus multichannel cochlear implant or the multichannel vibrotactile aid, Tactaid 7. DESIGN/METHODS:Imitative consonant productions of children with prelingual deafness were elicited and transcribed at two intervals: 1) before receiving their respective devices (predevice interval), and 2) after an average of 1.5 yr of device use (postdevice interval). The consonant productions were analyzed in terms of the percentage of consonant features (manner, place, and voicing) produced by the child that matched the features of the examiner's target. The percentage of features produced correctly was then averaged across repetitions, vowel environments, and participants within each group. RESULTS:At the predevice interval, the cochlear implant and Tactaid 7 participants demonstrated similar imitative consonant production abilities. After an average of 1.5 yr of device use, the cochlear implant participants demonstrated significantly greater gains than did the Tactaid 7 participants for the features of voicing and place of articulation. Although the cochlear implant participants showed a trend towards better production of the consonant manner features, this difference failed to reach significance. CONCLUSIONS:The current results suggest that the use of a multichannel sensory aid yields improvements in consonant feature production. Furthermore, use of a cochlear implant appears to promote the production of consonant voicing and place features to a greater degree than does the use of a multichannel tactile aid.