Faculty Bibliography

The neural mechanisms that support working memory (WM) depend on persistent neural activity. Within topographically organized maps of space in dorsal parietal cortex, spatially selective neural activity persists during WM for location. However, to date the necessity of these topographic subregions of human parietal cortex for WM remain unknown. To test the causal relationship of these areas to WM, we compared the performance of patients with lesions to topographically organized parietal cortex to controls on a memory-guided saccade (MGS) task as well as a visually-guided saccade (VGS) task. The MGS task allowed us to measure WM precision continuously with great sensitivity, while the VGS task allowed us to control for any deficits in general spatial or visuomotor processing. Compared to controls, patients generated memory-guided saccades that were significantly slower and less accurate, while visually-guided saccades were unaffected. These results provide key missing evidence for the causal role of topographic areas in human parietal cortex for WM, as well as the neural mechanisms supporting WM.

OBJECTIVE: To determine the prevalence and also accuracy of the laryngopharyngeal reflux (LPR) referring diagnosis and to determine the most useful clinical tool in arriving at the final diagnosis in a tertiary laryngology practice. STUDY DESIGN: Case series with planned data collection. SETTING: Six tertiary academic laryngology practices. SUBJECTS AND METHODS: We collected referring diagnosis and demographic information, including age, sex, ethnicity, referring physician, and whether or not patients had prior flexible laryngoscopy for 1077 patients presenting with laryngologic complaints from January 2010 and June 2013. Final diagnosis after the referred laryngologist's examination and the key diagnostic test used was then recorded. RESULTS: Of 1077 patients, 132 had a singular referring diagnosis of LPR. Only 47 of 132 patients (35.6%) had LPR confirmed on final primary diagnosis. Transnasal flexible laryngoscopy confirmed this in 27 of 47 (57.4%) patients. Eighty-five of 132 (64.4%) had a different final diagnosis than LPR. Sixty-five of 85 (76.5%) of these alternative pathologies were diagnosed with the aid of laryngeal stroboscopy. CONCLUSIONS: LPR appears to be an overused diagnosis for laryngologic complaints. For patients who have already had transnasal flexible laryngoscopic exams prior to their referral, laryngeal stroboscopy is the key diagnostic tool in arriving at the correct diagnosis.

PURPOSE: Posterior fossa ependymoma comprises two distinct molecular variants termed EPN_PFA and EPN_PFB that have a distinct biology and natural history. The therapeutic value of cytoreductive surgery and radiation therapy for posterior fossa ependymoma after accounting for molecular subgroup is not known. METHODS: Four independent nonoverlapping retrospective cohorts of posterior fossa ependymomas (n = 820) were profiled using genome-wide methylation arrays. Risk stratification models were designed based on known clinical and newly described molecular biomarkers identified by multivariable Cox proportional hazards analyses. RESULTS: Molecular subgroup is a powerful independent predictor of outcome even when accounting for age or treatment regimen. Incompletely resected EPN_PFA ependymomas have a dismal prognosis, with a 5-year progression-free survival ranging from 26.1% to 56.8% across all four cohorts. Although first-line (adjuvant) radiation is clearly beneficial for completely resected EPN_PFA, a substantial proportion of patients with EPN_PFB can be cured with surgery alone, and patients with relapsed EPN_PFB can often be treated successfully with delayed external-beam irradiation. CONCLUSION: The most impactful biomarker for posterior fossa ependymoma is molecular subgroup affiliation, independent of other demographic or treatment variables. However, both EPN_PFA and EPN_PFB still benefit from increased extent of resection, with the survival rates being particularly poor for subtotally resected EPN_PFA, even with adjuvant radiation therapy. Patients with EPN_PFB who undergo gross total resection are at lower risk for relapse and should be considered for inclusion in a randomized clinical trial of observation alone with radiation reserved for those who experience recurrence.

Cochlear implants are neuroprosthetic devices that provide hearing to deaf patients, although outcomes are highly variable even with prolonged training and use. The central auditory system must process cochlear implant signals, but it is unclear how neural circuits adapt - or fail to adapt - to such inputs. Understanding these mechanisms is required for development of next-generation neuroprosthetics that interface with existing neural circuits and enable synaptic plasticity to improve perceptual outcomes. Here we describe a new system for cochlear implant insertion, stimulation, and behavioral training in rats. Animals were first ensured to have significant hearing loss via physiological and behavioral criteria. We developed a surgical approach for multi-channel (2-channel or 8-channel) array insertion, comparable to implantation procedures and depth in humans. Peripheral and cortical responses to stimulation were used to objectively program the implant. Animals fitted with implants learned to use them for an auditory-dependent task that assesses frequency detection and recognition, in a background of environmentally- and self-generated noise, and ceased responding appropriately to sounds when the implant was temporarily inactivated. This physiologically-calibrated and behaviorally-validated system provides a powerful opportunity to study the neural basis of neuroprosthetic device use and plasticity.

OBJECTIVE: The aim of this case series was to assess the impact of auditory rehabilitation with cochlear implantation on the cognitive function of elderly patients over time. DESIGN: This is a longitudinal case series of prospective data assessing neurocognitive function and speech perception in an elderly cohort pre- and post-implantation. SETTING: University cochlear implant center. PARTICIPANTS: The patients were post-lingually deafened elderly female (mean, 73.6 years; SD, 5.82; range, 67-81 years) cochlear implant recipients (n=7). MEASUREMENTS: A neurocognitive battery of 20 tests assessing intellectual function, learning, short- and long-term memory, verbal fluency, attention, mental flexibility, and processing speed was performed prior to and 2-4.1 years (mean, 3.7) after cochlear implant (CI). Speech perception testing using Consonant-Nucleus-Consonant words was performed prior to implantation and at regular intervals postoperatively. Individual and aggregate differences in cognitive function pre- and post-CI were estimated. Logistic regression with cluster adjustment was used to estimate the association (%improvement or %decline) between speech understanding and years from implantation at 1 year, 2 years, and 3 years post-CI. RESULTS: Improvements after CI were observed in 14 (70%) of all subtests administered. Declines occurred in five (25%) subtests. In 55 individual tests (43%), post-CI performance improved compared to a patient's own performance before implantation. Of these, nine (45%) showed moderate or pronounced improvement. Overall, improvements were largest in the verbal and memory domains. Logistic regression demonstrated a significant relationship between speech perception and cognitive function over time. Five neurocognitive tests were predictive of improved speech perception following implantation. CONCLUSION: Comprehensive neurocognitive testing of elderly women demonstrated areas of improvement in cognitive function and auditory perception following cochlear implantation. Multiple neurocognitive tests were strongly associated with current speech perception measures. While these data shed light on the complex relationship between hearing and cognition by showing that CI may slow the expected age-related cognitive decline, further research is needed to examine the impact of hearing rehabilitation on cognitive decline.

Importance: Septal deviation commonly occurs in patients with cleft lip and palate (CLP); however, the contribution of the cartilaginous and bony septum to airway obstruction in skeletally mature patients is poorly understood. Objectives: To describe the internal nasal airway anatomy of skeletally mature patients with CLP and to determine the contributors to airway obstruction. Design, Setting, and Participants: This single-center retrospective review included patients undergoing cone-beam computed tomography (CBCT) from November 1, 2011, to July 6, 2015, at the cleft lip and palate division of a major academic tertiary referral center. Patients met inclusion criteria for the study if they were at least 15 years old at the time of CBCT, and images were used only if they were obtained before Le Fort I osteotomy and/or formal septorhinoplasty. Twenty-four skeletally mature patients with CLP and 16 age-matched control individuals were identified for the study. Main Outcomes and Measures: Septal deviation and airway stenosis were measured in the following 3 coronal sections: at the cartilaginous septum (anterior nasal spine), bony septum (posterior nasal spine), and midpoint between the anterior and posterior nasal spine. The perpendicular plate of the ethmoid bone and vomer displacement were measured as angles from the vertical plane at the coronal section of maximal septal deviation. The site of maximal septal deviation was identified. Results: Among the 40 study participants, 26 were male. The mean (SD) age was 21 (5) and 23 (6) years for patients with CLP and controls, respectively. Septal deviation in patients with CLP was significantly worse than that of controls at the anterior nasal spine (2.1 [0.5] vs 0.8 [0.2] mm; P < .05) and posterior nasal spine (2.9 [0.5] vs 1.0 [0.3] mm; P < .01) and most severe at the midpoint (mean [SD], 4.4 [0.6] vs 2.1 [0.3] mm; P < .01). The point of maximal septal deviation occurred in the bony posterior half of the nasal airway in 27 of 40 patients (68%). The CLP bony angular deviation from the vertical plane was significant in the CLP group compared with the control group (perpendicular plate of the ethmoid bone, 14 degrees [2 degrees ] vs 8 degrees [1 degrees ]; vomer, 34 degrees [5 degrees ] vs 13 degrees [2 degrees ]; P < .05 for both), and vomer deviation was significantly associated with anterior nasal airway stenosis (r = -0.61; P < .01). Conclusions and Relevance: Skeletally mature patients with CLP have significant septal deviation involving bone and cartilage. Resection of the bony and cartilaginous septum should be considered at the time of definitive cleft rhinoplasty. Level of Evidence: NA.

Brain tumors collectively represent the most common solid tumors in childhood and account for significant morbidity and mortality. Until recently, pediatric brain tumors were diagnosed and classified solely based on histologic criteria, and treatments were chosen empirically. Recent research has greatly enhanced our understanding of the diverse biology of pediatric brain tumors, their molecular and genetic underpinnings, leading to improved diagnostic accuracy and risk stratification, as well as the development of novel biomarkers and molecular targeted therapies. For subsets of patients, these new treatment options have already resulted in improved survival and decreased treatment toxicity. In this article, we provide an overview of the most common childhood brain tumors, describe recent key advances in the field, and discuss the therapeutic challenges that remain.

The zebra finch brain features a set of clearly defined and hierarchically arranged motor nuclei that are selectively responsible for producing singing behavior. One of these regions, a critical forebrain structure called HVC, contains premotor neurons that are active at precise time points during song production. However, the neural representation of this behavior at a population level remains elusive. We used two-photon microscopy to monitor ensemble activity during singing, integrating across multiple trials by adopting a Bayesian inference approach to more precisely estimate burst timing. Additionally, we examined spiking and motor-related synaptic inputs using intracellular recordings during singing. With both experimental approaches, we find that premotor events do not occur preferentially at the onsets or offsets of song syllables or at specific subsyllabic motor landmarks. These results strongly support the notion that HVC projection neurons collectively exhibit a temporal sequence during singing that is uncoupled from ongoing movements.

Motor axons approach muscles that are prepatterned in the prospective synaptic region. In mice, prepatterning of acetylcholine receptors requires Lrp4, a LDLR family member, and MuSK, a receptor tyrosine kinase. Lrp4 can bind and stimulate MuSK, strongly suggesting that association between Lrp4 and MuSK, independent of additional ligands, initiates prepatterning in mice. In zebrafish, Wnts, which bind the Frizzled (Fz)-like domain in MuSK, are required for prepatterning, suggesting that Wnts may contribute to prepatterning and neuromuscular development in mammals. We show that prepatterning in mice requires Lrp4 but not the MuSK Fz-like domain. In contrast, prepatterning in zebrafish requires the MuSK Fz-like domain but not Lrp4. Despite these differences, neuromuscular synapse formation in zebrafish and mice share similar mechanisms, requiring Lrp4, MuSK, and neuronal Agrin but not the MuSK Fz-like domain or Wnt production from muscle. Our findings demonstrate that evolutionary divergent mechanisms establish muscle prepatterning in zebrafish and mice.