Faculty Bibliography

Critical periods are times of pronounced brain plasticity. During a critical period in the postnatal development of the visual cortex, the occlusion of one eye triggers a rapid reorganization of neuronal responses, a process known as ocular dominance plasticity. We have shown that the transplantation of inhibitory neurons induces ocular dominance plasticity after the critical period. Transplanted inhibitory neurons receive excitatory synapses, make inhibitory synapses onto host cortical neurons, and promote plasticity when they reach a cellular age equivalent to that of endogenous inhibitory neurons during the normal critical period. These findings suggest that ocular dominance plasticity is regulated by the execution of a maturational program intrinsic to inhibitory neurons. By inducing plasticity, inhibitory neuron transplantation may facilitate brain repair

Short-term changes in synaptic gain support information processing throughout the CNS, yet we know little about the developmental regulation of such plasticity. Here we report that auditory experience is necessary for the normal maturation of synaptic inhibitory short-term plasticity (iSTP) in the auditory cortex, and that presynaptic GABA(B) receptors regulate this development. Moderate or severe hearing loss was induced in gerbils, and iSTP was characterized by measuring inhibitory synaptic current amplitudes in response to repetitive stimuli. We reveal a profound developmental shift of iSTP from depressing to facilitating after the onset of hearing. Even moderate hearing loss prevented this shift. This iSTP change was mediated by a specific class of inhibitory interneurons, the low-threshold spiking cells. Further, using paired recordings, we reveal that presynaptic GABA(B) receptors at interneuron-pyramidal connections regulate iSTP in an experience-dependent manner. This novel synaptic mechanism may support the emergence of mature temporal processing in the auditory cortex

INTRODUCTION: Global health education is becoming more important for developing well-rounded physicians and may encourage students toward a career in primary care. Many medical schools, however, lack adequate and structured opportunities for students beginning the curriculum. METHODS: Second-year medical students initiated, designed, and facilitated a pass-fail international health elective, providing a curricular framework for preclinical medical students wishing to gain exposure to the clinical and cultural practices of a developing country. RESULTS: All course participants (N=30) completed a post-travel questionnaire within one week of sharing their experiences. Screening reflection essays for common themes that fulfill university core competencies yielded specific global health learning outcomes, including analysis of health care determinants. CONCLUSION: Medical students successfully implemented a sustainable global health curriculum for preclinical student peers. Financial constraints, language, and organizational burdens limit student participation. In future, long-term studies should analyze career impact and benefits to the host country.

OBJECTIVES/HYPOTHESIS: To identify contemporary indications, treatment principles, technique, injection materials, complications, and success rates of vocal fold injection augmentation. STUDY DESIGN: Multi-institutional retrospective review. METHODS: Records of patients undergoing injection augmentation at seven university medical centers from July 2007 through June 2008 were reviewed for information regarding diagnosis, unilateral or bilateral injection, route of injection, anesthesia, treatment site (office or operating room), material used, reason for technique selected, and technical success. RESULTS: In 12 months, 460 injections were performed, 236 (51%) in awake, unsedated patients, and 224 (49%) under general anesthesia. Indications included vocal fold paralysis (248; 54%), paresis (97; 21%), atrophy (68; 15%) and scar (47; 10%). Scar was more likely to be treated in the operating room (P = .000052). In awake patients, 112 (47%) injections were performed by transcricothyroid approach, 55 (23%) by peroral approach, 49 (21%) by transthyrohyoid membrane approach, and 20 (8%) by transthyroid cartilage approach. Neither technical success rate (99% vs. 97%) nor complication rate (3% vs. 2%) differed between awake and asleep techniques. The most common materials in the clinic setting were methylcellulose (35%), bovine collagen (28%), and calcium hydroxylapatite (26%); in the operating room these were calcium hydroxylapatite (36%) and methylcellulose (35%). Calcium hydroxylapatite was more likely to be used under general anesthesia (P = .019). Five-year data show that the use of injection in the awake patient rose from 11% to 43% from 2003 to 2008. CONCLUSIONS: Injection augmentation remains a safe, effective, and clinically practical treatment with a high rate of success, whether performed in the awake or asleep patient. The rapid adoption of awake injection over the past 5 years speaks to its clinical utility. Complication rates are low and equivalent to those under general anesthesia. Otolaryngologists continue to use a variety of techniques and materials to treat a range of conditions of glottic insufficiency.

OBJECTIVE: To compare outcomes with the use of thyroid ala cartilage (TAC) and costal cartilage (CC) grafts in pediatric primary anterior laryngotracheoplasty (LTP). DESIGN: Retrospective comparison study. SETTING: Tertiary, academic children's hospital. PATIENTS: Of 45 laryngotracheal operations performed between June 2001 and October 2008 for laryngotracheal stenosis, 29 were primary anterior LTPs. The procedures used either TAC (n = 24) or CC (n = 5) grafts and were planned as either single-stage (TAC group, 22 patients; CC group, 2 patients) or multistage (TAC group, 2 patients; CC group, 3 patients). MAIN OUTCOME MEASURES: Operative time, length of intubation, graft-specific complications, need for additional airway procedures, and overall decannulation rate. RESULTS: The mean (SD) operative times were 222 (56) minutes for TAC grafts and 363 (59) minutes for CC grafts (P = .005). For single-stage LTPs that were decannulated, the mean (range) length of intubation was 3.3 (1-11) days for TAC grafts (n = 18) and 3 (1-5) days for CC grafts (n = 2) (P = .90). Graft-specific complications occurred in 17% of TAC grafts (n = 4) and 20% of CC grafts (n = 1) (alpha > 0.05). Symptomatic stenosis requiring additional surgical intervention occurred in 43% of TAC grafts (n = 10) and 60% of CC grafts (n = 3) (alpha > 0.05). Patients underwent decannulation in 83% of TAC grafts (n = 19) and 80% of CC grafts (n = 4) (alpha > 0.05). CONCLUSIONS: In primary anterior LTPs, TAC grafts require significantly less operative time than CC grafts (P = .005). There were no statistically significant differences in length of intubation, frequency of graft-specific complications, or decannulation rates between TAC and CC grafts in primary anterior LTPs.

The effect of feedback and materials on perceptual learning was examined in listeners with normal hearing who were exposed to cochlear implant simulations. Generalization was most robust when feedback paired the spectrally degraded sentences with their written transcriptions, promoting mapping between the degraded signal and its acoustic-phonetic representation. Transfer-appropriate processing theory suggests that such feedback was most successful because the original learning conditions were reinstated at testing: Performance was facilitated when both training and testing contained degraded stimuli. In addition, the effect of semantic context on generalization was assessed by training listeners on meaningful or anomalous sentences. Training with anomalous sentences was as effective as that with meaningful sentences, suggesting that listeners were encouraged to use acoustic-phonetic information to identify speech than to make predictions from semantic context

A simple mathematical model is presented that predicts vowel identification by cochlear implant users based on these listeners' resolving power for the mean locations of first, second, and/or third formant energies along the implanted electrode array. This psychophysically based model provides hypotheses about the mechanism cochlear implant users employ to encode and process the input auditory signal to extract information relevant for identifying steady-state vowels. Using one free parameter, the model predicts most of the patterns of vowel confusions made by users of different cochlear implant devices and stimulation strategies, and who show widely different levels of speech perception (from near chance to near perfect). Furthermore, the model can predict results from the literature, such as Skinner, et al. [(1995). Ann. Otol. Rhinol. Laryngol. 104, 307-311] frequency mapping study, and the general trend in the vowel results of Zeng and Galvin's [(1999). Ear Hear. 20, 60-74] studies of output electrical dynamic range reduction. The implementation of the model presented here is specific to vowel identification by cochlear implant users, but the framework of the model is more general. Computational models such as the one presented here can be useful for advancing knowledge about speech perception in hearing impaired populations, and for providing a guide for clinical research and clinical practice

OBJECTIVES/HYPOTHESIS: Anatomic variants of the jugular bulb (JB) are common; however, abnormalities such as large high riding JB and JB diverticulum (JBD) are uncommon. Rarely, the abnormal JB may erode into the inner ear. The goal of our study is to report a large series of patients with symptomatic JB erosion into the inner ear. STUDY DESIGN: Retrospective review in an academic medical center. METHODS: Eleven patients with JB abnormality eroding into the inner ear were identified on computed tomography (CT) scan of the temporal bone. RESULTS: Age at presentation was from 5 years to 82 years with six males and five females. The large JB or JBD eroded into the vestibular aqueduct (n = 9) or the posterior semicircular canal (n = 4). The official radiology report usually identified the JB abnormality; however, erosion into these structures by the JB was not mentioned in all but one case. All patients were symptomatic with five having conductive hearing loss (CHL) and three complaining of pulsatile tinnitus. Those with pulsatile tinnitus and four of five with CHL had erosion into the vestibular aqueduct. Vestibular evoked myogenic potential (VEMP) findings in three of six patients were consistent with dehiscence of the inner ear. CONCLUSIONS: High riding large JB or JBD can erode into the inner ear and may be associated with CHL and/or pulsatile tinnitus. CT scan is diagnostic and should be examined specifically for these lesions. As patients with pulsatile tinnitus may initially undergo a magnetic resonance imaging scan, identification of JB abnormality should prompt CT scan or VEMP testing to evaluate for inner ear erosion