Psychoacoustical contribution of each lateral lemniscus.

Although each lateral lemniscus is required for sound localization in its contralateral hemifield, no auditory function is yet known for the neural activity evoked in the lemniscus ipsilateral to a sound source. In an attempt to assess the role played by the ipsilateral lemniscus, monaural cats were tested on an array of psychoacoustical tasks before and after surgical section of one or the other lateral lemniscus. The results show that the lemniscus contralateral to the remaining intact ear is either necessary or sufficient for 24 of the 26 tests administered. However, the lemniscus ipsilateral to the intact ear is both necessary and sufficient (or alternatively, the contralateral lemniscus makes no obvious contribution) to normal thresholds in two of the tasks: detection of low-frequency tones (< 4 kHz) and detection of low-frequency AM modulation. Because of their projections to the ipsilateral inferior colliculus via the ipsilateral lemniscus, the anatomical substrate of these two unusual tasks is probably the fibers from the MSO and possibly, the LSO, ipsilateral to the intact ear.     

Developmental changes in physiological properties in the rat's dorsal nucleus of the lateral lemniscus

To better understand the development of the dorsal nucleus of the lateral lemniscus (DNLL), intrinsic membrane properties and synaptic responses of DNLL neurons in brain slice preparations were examined. Intracellular recordings were taken from DNLL neurons of rat pups at postnatal days 4-8 (early group), 10-12 (intermediate group) and 16-18 (late group). In response to positive current injection, neurons in the early group displayed firing with lower frequency and a longer action potential duration in comparison to the intermediate and late groups. The action potential amplitude of DNLL neurons increased during development. Postsynaptic potentials (PSPs), with excitatory predominance, were elicited by electrical stimulation of the lateral lemniscus and commissure of Probst throughout the three age groups. Neurons showed a longer latency and rise time of the PSPs in the early group in comparison with those in the intermediate and late groups. These results suggest that the early DNLL neurons display physiological characteristics associated with immature neurons, while the other two groups tend to illustrate mature-like neuronal properties. Furthermore, it seems that the neurons at day 10-12 are in a transitional period of development, which coincides with the onset of hearing.     

Auditory discrimination: The relationship between psychophysical and electrophysiological measures

Abstract

Objectives: This study aimed to (1) investigate the relationship between the acoustic change complex (ACC) and perceptual measures of frequency and intensity discrimination, and gap detection; and (2) examine the effects of acoustic change on the amplitudes and latencies of the ACC. Design: Psychophysical thresholds for frequency and intensity discrimination and gap detection, as well as ACCs elicited by stimuli containing increments in frequency, or intensity or gaps, were recorded from the same group of subjects. The magnitude of the acoustic change was systematically varied for the ACC recording. Study sample: Twenty-six adults with normal hearing, ranging in age between 19 and 39 years. Results: Electrophysiological and psychophysical measures for frequency and intensity discrimination were significantly correlated. Electrophysiological thresholds were comparable to psychophysical thresholds for intensity discrimination but were higher than psychophysical thresholds for gap detection and frequency discrimination. Increasing the magnitude of acoustic change increased the ACC amplitude but did not show consistent effects across acoustic dimensions for ACC latency. Conclusions: The ACC can be used as an objective index of auditory discrimination in frequency and intensity. The ACC amplitude is a better indicator for auditory processing than the ACC latency.     

Monaural and binaural processing in the ventral nucleus of the lateral lemniscus: a major source of inhibition to the inferior colliculus

The ventral nucleus of the lateral lemniscus (VNLL) is a major source of input to the inferior colliculus. This paper reviews recent studies of neural responses in the VNLL of the unanesthetized rabbit. The VNLL has generally been viewed as a monaural nucleus, with its neurons responding primarily to stimulation of the contralateral ear. In the rabbit, the VNLL is divided into a medial division (VNLLm) comprising neurons intercalated in the medial limb of the lemniscus, a compact lateral division (VNLLl), and a dorsal division. The VNLLm contains an abundance of neurons sensitive to interaural temporal disparities (ITDs), one of the major binaural cues for sound localization. These neurons respond only at the onset of tones, and therefore appear to encode the ITDs of transients. Even in the VNLLl, many neurons are sensitive to binaural stimulation. The VNLLl contains a variety of neurons with different discharge patterns, the two most common of which are sustained and onset. The discharge patterns, frequency-tuning and dynamic ranges of VNLLl neurons indicate that this division is able to supply the inferior colliculus with a variety of inputs, each serving a different function in the analysis of sound.     

Assessment of the Auditory Handicap in adults with unilateral hearing loss

Hearing impairment (HI) is characterized by unilateral hearing loss in one ear and can result in learning difficulties, language impairment and socio-emotional difficulties. To assess the perception of hearing handicap in adult subjects, patients with unilateral sensorineural HI, non-users of individual hearing aids.     

Auditory performance of children with unilateral sensorineural hearing loss

Horizontal sound localization and syllable recognition skills were examined in a group of children with unilateral sensorineural hearing loss and a matched group of normal hearers. The results showed that the unilaterally hearing-impaired children performed more poorly than the normal counterparts in both localization and speech recognition of nonsense syllables. The unilaterally hearing-impaired children had considerable difficulty understanding in a background of noise. The clinical implications of these findings are discussed.     

Synaptic transmission mediated by ionotropic glutamate, glycine and GABA receptors in the rat's ventral nucleus of the lateral lemniscus

The synaptic pharmacology of the ventral nucleus of the lateral lemniscus (VNLL) was investigated in brain slices obtained from rats of 14-37 days old using intracellular recording techniques. Excitatory and inhibitory synaptic potentials (EPSPs and IPSPs) were elicited by electrical stimulation of the lemniscal pathway and recorded from neurons with five types of intrinsic firing patterns (onset, pause, adapting, regular and bursting types). Synaptic receptors that mediated the EPSPs and IPSPs were identified using AMPA, NMDA, GABA(A) and glycine receptor antagonists. The early/short EPSPs were mediated by AMPA receptors. The late/long EPSPs, encountered only in neurons of younger animals, were mediated by NMDA receptors. The IPSPs in most neurons were mediated by glycine receptors. In some neurons the IPSPs were mediated by GABA(A) receptors or both glycine and GABA(A) receptors. The temporal dynamics of fast AMPA EPSPs and glycinergic IPSPs were very similar. AMPA EPSPs and glycinergic (and/or GABAergic) IPSPs could be encountered in a single neuron. The results suggest that the VNLL not only relays incoming signals rapidly from the lower brainstem to the inferior colliculus, but also integrates excitatory and inhibitory inputs to modify and process auditory information.     

Management of the lateral frontal sinus lesion and the supraorbital cell mucocele

BACKGROUND: Masses that radiographically appear in the lateral aspect of the frontal sinus can be difficult to access and often are approached through external approaches. Supraorbital ethmoid cells pneumatize the orbital plate of the ethmoid bone to lie posterior and lateral to the frontal sinus. Opacification of a supraorbital cell may radiographically give the appearance of a laterally based frontal sinus lesion. Often, these represent mucoceles, in which their drainage can be achieved through endoscopic techniques and without the need for an external approach. METHODS: Retrospective review of patients treated for lateral frontal sinus lesions at a tertiary sinus center was performed. Radiology, endoscopic findings, operative reports, and patient symptoms were reviewed. RESULTS: Ten patients were identified with lateral frontal sinus lesions based on radiography of the paranasal sinuses and nasal endoscopy. All patients were determined to be supraorbital mucoceles. These patients underwent surgical drainage using computer-aided endoscopic techniques. Initially, endoscopic drainage of the mucocele was successful in all patients. One patient was lost to follow-up after 3 months and one patient underwent a revision endoscopic surgery with trephination 5 months after the initial drainage. The remaining eight patients remain free of disease by nasal endoscopy and postoperative computed tomography scans (median follow-up of 25 months; range, 8-38 months). CONCLUSION: Knowledge of the anatomy of the ethmoid complex and presence of various cells within the frontal recess such as supraorbital cells are important in the management of the laterally based frontal sinus lesion. Often, these lesions may represent supraorbital cell mucoceles amenable to endoscopic drainage. Given the nature of mucoceles, long-term follow-up is needed before endoscopic drainage of these lesions can be validated. However, preliminary data suggest that an endoscopic approach provides for adequate drainage and helps avoid external approaches.     

Auditory thresholds in rats of different age and strain. A behavioral and electrophysiological study

The auditory sensitivity of albino rats was determined behaviorally by conditioned suppression of licking and electrophysiologically by the auditory brain stem response (ABR). The behavioral thresholds were obtained with 10-Hz frequency-modulated tones, and the ABR with $\text{1}\text{1}$- or $\text{1}\text{3}\text{-}\text{octave}$ filtered sine waves. Individual variability, reproducibility of responses and the influence of sex, age and strain were investigated. The behavioral and electrophysiological techniques were compared in animals with noise-induced high-frequency hearing losses. The results showed the highest degree of normal auditory sensitivity to be around 12–24 kHz. The variability in 20 rats was about 15 dB. In young animals, strain and sex had no influence. A deterioration in high-frequency hearing sensitivity was observed in aged hypertensive rats, whereas normotensive ones showed only minimal changes. The thresholds obtained with the electrophysiological (ABR) technique were 10–20 dB higher than those obtained behaviorally. Both techniques (behavioral and $\text{1}\text{3}\text{-}\text{octave}$ ABR) assess high-frequency hearing loss equally well. It was concluded that the ABR ($\text{1}\text{3}\text{-}\text{octave}$ filtered sine waves) is suitable for the determination of hearing thresholds and the assessment of hearing loss, at least in the high-frequency range. The ABR technique is especially useful in long-term experiments during which thresholds are determined repeatedly.     

闭目踏步试验对单侧外周前庭损伤的定侧价值

目的 探讨闭目踏步试验对单侧前庭病变的定侧价值.方法 可定病变侧别的单侧前庭外周功能损伤患者126例,其中颞骨外伤11例,突发性聋伴眩晕94例,前庭神经炎21例;健康对照组50例.原地闭目踏步50步,发生倾倒,侧移1 m或偏转＞45°为存在偏向.实验数据采用SPSS13.0软件进行x2检验.结果 126例患者中50.0%(63/126)偏向患侧,24.6%(31/126)偏向健侧,25.4%(32/126)无偏向.发病3 d内的23例患者中偏向健侧39.1%(9/23),偏向患侧39.1%(9/23),21.8%(5/23)无偏向;随着时间的延长,偏向患侧和无偏向的比例增大,病程超过1个月的22例患者中1例偏向健侧,病程超过2个月的患者不再偏向健侧.发病1周内偏向健侧的17例患者,在随访的2周内,35.3%变为偏向患侧.观察到自发性眼震的35例患者中22.9%(8/35)闭目踏步偏向和自发性眼震同侧.结论 急性外周前庭受损不能根据闭目踏步试验偏向进行患侧的确定,要根据症状和其他检查一起综合考虑.     

Spatial representation of frequency in the rat dorsal nucleus of the lateral lemniscus as revealed by acoustically induced c-fos mRNA expression

The conventional view, based largely on studies in cats, holds that the dorsal nucleus of the lateral lemniscus (DNLL) is tonotopically organized with a dorsal (low-frequency) to ventral (high-frequency) representation. Based on the topography of projections between the DNLL and inferior colliculus, it has been proposed that the rat DNLL has a concentric, inside-to-outside, tonotopic organization with high frequencies represented along the rind and low frequencies represented in the core. We used acoustic stimulation and c-fos mRNA expression to examine this issue. Results suggest that the rat DNLL does have a crude tonotopic organization and that this tonotopy has a concentric component. Following high-frequency stimulation, labeled neurons were found most frequently along the margins of DNLL, although they also tended to be more concentrated ventrally. Many fewer neurons labeled following middle-frequency stimulation, and these tended to be more uniformly distributed throughout the nucleus. Still fewer neurons labeled after low-frequency stimulation and these tended to be scattered mostly in the dorsal half of the nucleus. We conclude that: (i) many more neurons in the rat DNLL are responsive to high-frequency than to low-frequency acoustic stimulation; and (ii) that the frequency representation of the rat DNLL has both concentric and dorsal-to-ventral components.     

单侧上颌窦占位性病变的CT诊断

目的探讨CT扫描对常见的单侧上颌窦占位性病变的诊断意义。方法回顾性总结2006年1月～2008年1月我科治疗的108例单侧上颌窦占位性病变患者的临床及影像学资料,并以组织病理学结果作为对照,对比分析CT扫描在单侧上颌窦占位性病变中的诊断意义。结果108例单侧上颌窦占位性病变中慢性上颌窦炎36例（33．3％）,上颌窦肿瘤32例（29．6％）,真菌性上颌窦炎19例（17．6％）,上颌窦囊肿14例（13．0％）,上颌窦后鼻孔息肉5例（4．6％）,上颌窦出血坏死性息肉及上颌窦嗜酸性肉芽肿各1例（0．9％）。大多数上颌窦占位性病变都具有其特有的临床及影像学表现,鼻窦CT扫描在单侧上颌窦占位性病变的术前诊断总体准确率为79．1％;其中上颌窦囊肿的术前诊断准确率为92．9％,慢性上颌窦炎为90．0％,上颌窦癌为80．0％,真菌性上颌窦炎为86．4％,鼻内翻性乳头瘤为50．0％。结论CT扫描对单侧上颌窦占位性病变的术前诊断有着十分重要的作用,大多数病变通过鼻窦CT检查可以作出初步的定位或定性诊断,并制定出合理的手术方案,最终确诊仍有赖于组织病理学检查。     

Auditory localization under conditions of unilateral fitting of different hearing aid systems.

The spatial localization function of hearing-impaired listeners, usually fitted bilaterally with BTE, ITE or ITC devices, was tested under conditions of unilateral fitting of each of their own hearing aids, and unilateral fitting of stock versions of each of the other types. For the BTE wearers average localization accuracy and individual variability were not greatly changed when wearing only their left ear device, compared with bilateral aided performance. In ITE wearers, unilateral fitting in either ear led to somewhat poorer performance than bilateral. In the ITC wearers unilateral fitting produced inconsistent outcomes. Both BTE and ITE wearers fared poorly when fitted unilaterally with stock forms of devices 'foreign' to them, whereas ITC wearers did not show such a contrasting outcome. A group of non-impaired listeners showed severe disruption of localization under unilateral BTE and ITC hearing aid conditions, and to a lesser extent with ITEs. Results for the hearing-impaired listeners are interpreted in terms of adaptation to different usage patterns, with BTE wearers suggested as having adapted to their own systems unilaterally as well as bilaterally.     

Auditory cortical response patterns to multiple rhythms of AM sound

OBJECTIVE: Multiple amplitude modulation (AM) of a tone results in a time series with a complex structure of envelope fluctuations. In this study the cortical responses elicited by such an auditory stimulus were investigated. It was hypothesized that the auditory cortex responds simultaneously with different patterns of activity corresponding to the different rhythm of periodical stimulus fluctuations. The relations of these response patterns to either steady-state responses (SSR) in the 40 Hz range or the transient slow auditory evoked responses were investigated. DESIGN: Auditory evoked magnetic fields were recorded from the left temporal cortex of nine healthy humans in response to 250 Hz tones that were amplitude modulated with the sum of two sinusoids of 38 and 40 Hz. The stimulus was presented continuously to the subject's right ear at the intensity of 70 dB sensation level. In addition, the responses to 250 Hz tone-burst stimuli with duration of 20, 50, 100, and 200 msec, respectively, were recorded. The tone-bursts were presented at an inter-stimulus interval (ISI) of 0.5 sec, which was equivalent to the slowest rhythm of the multiple-AM stimulus. Magnetic source analysis was applied to all elicited waveforms. RESULTS: From all subjects SSR at 38 and 40 Hz were clearly recognizable and were superimposed by a periodical response pattern corresponding to 2 Hz stimulus envelope fluctuations. A positive peak with latency of 70 msec was the mostly pronounced response to tone-burst stimulation at the ISI of 0.5 sec and resembles the low-frequency response pattern to the AM stimulus. The N1-P2 complex showed an almost complete suppression at 0.5 sec ISI. In contrast, it was the most prominent evoked response activity when using a longer ISI of 3 sec. Source locations in overlapping areas were estimated for the SSR in the 40 Hz range, the prominent peak of low-frequency response to the AM stimulus, and the P1 peak at tone-burst stimulation, respectively. These were separated from the N1 source location by about 0.5 cm in anterior and 0.5 cm in medial direction. CONCLUSION: As a result of multiple AM the stimulus signal envelope fluctuates with frequencies of 2 Hz and around 40 Hz. The auditory cortex responds to this stimulus with different response patterns. Both modulation signals at 38 and 40 Hz were almost linearly represented as steady-state responses. The evoked response patterns to stimulus fluctuations at low-frequency rhythm resemble the slow cortical auditory evoked responses. The 2 Hz stimulus rhythm is perceived as loudness fluctuation, and 40 Hz modulation is perceived as a rough sound. It is assumed that the different cortical representations correspond to both types of perception of the complex AM sound.     

Auditory Brainstem Evoked Response: response patterns of full-term and premature infants

Auditory Brainstem Response (ABR) is important for the early diagnosis of hearing impairment in infants.AimTo compare ABR responses in full-term and premature infants; gender and ear were taken into account.MethodsA cross-sectional prospective cohort study was carried out. We evaluated 36 full-term and 30 premature infants that had passed the Transient Otoacoustic Emissions test, had type A tympanometric curves, and had no risk factor for hearing loss besides prematurity. The evaluations were done from the time of hospital discharge to the third month of life, and consisted of a clinical history, acoustic immittance testing and ABR evaluation.ResultsThe comparison of absolute and interpeak wave I, III and V latencies in right and left ears revealed a statistically significant difference at the interpeak I-III. There was no significant gender differences in the comparison of results. Significant difference in wave I, III and V absolute latencies at 80 dB and in wave V at 60 db and 20 db were observed in a comparison of absolute and interpeak latencies between full-term and premature infants. An inverse correlation was found between age and absolute latencies.ConclusionsThe maturity of the auditory system influences ABR responses in infants. To avoid misinterpretation of results, gestational age must be taken into account in the analysis of ABR in pediatric population.     

Teaching and practice patterns of lateral osteotomies for rhinoplasty

Purpose

Lateral osteotomies are important during rhinoplasty and represent a challenging technique that otolaryngology and plastic surgery trainees must learn. The approaches for osteotomies are difficult to teach as they are accomplished through tactile feedback. Trends in teaching and practice patterns of lateral osteotomies are poorly described in the literature, and this study aims to fill this knowledge gap.

Afferents to the cochlear nuclei and nucleus laminaris from the ventral nucleus of the lateral lemniscus in the zebra finch (Taeniopygia guttata)

The presence and nature of a descending projection from the ventral nucleus of the lateral lemniscus (LLV) to the cochlear nuclei (NA, NM) and the third-order nucleus laminaris (NL) was investigated in a songbird using tract tracing and GAD immunohistochemistry. Tracer injections into LLV produced anterograde label in the ipsilateral NA, NM and NL, which was found not to be GABAergic. Double retrograde labeling from LLV and NA/NM/NL ruled out the possibility that the LLV projection actually arose from collaterals of superior olivary projections to NA/NM/NL. The LLV projection may be involved in the discrimination of laterality of auditory input.