Auditory Cortical Images of Tones and Noise Bands

We examined the representation of stimulus center frequencies by the distribution of cortical activity. Recordings were made from the primary auditory cortex (area A1) of ketamine-anesthetized guinea pigs. Cortical images of tones and noise bands were visualized as the simultaneously recorded spike activity of neurons at 16 sites along the tonotopic gradient of cortical frequency representation. The cortical image of a pure tone showed a restricted focus of activity along the tonotopic gradient. As the stimulus frequency was increased, the location of the activation focus shifted from rostral to caudal. When cochlear activation was broadened by increasing the stimulus level or bandwidth, the cortical image broadened. An artificial neural network algorithm was used to quantify the accuracy of center-frequency representation by small populations of cortical neurons. The artificial neural network identified stimulus center frequency based on single-trial spike counts at as few as ten sites. The performance of the artificial neural network under various conditions of stimulus level and bandwidth suggests that the accuracy of representation of center frequency is largely insensitive to changes in the width of cortical images.     

Predicting Perception in Noise Using Cortical Auditory Evoked Potentials

Speech perception in background noise is a common challenge across individuals and health conditions (e.g., hearing impairment, aging, etc.). Both behavioral and physiological measures have been used to understand the important factors that contribute to perception-in-noise abilities. The addition of a physiological measure provides additional information about signal-in-noise encoding in the auditory system and may be useful in clarifying some of the variability in perception-in-noise abilities across individuals. Fifteen young normal-hearing individuals were tested using both electrophysiology and behavioral methods as a means to determine (1) the effects of signal-to-noise ratio (SNR) and signal level and (2) how well cortical auditory evoked potentials (CAEPs) can predict perception in noise. Three correlation/regression approaches were used to determine how well CAEPs predicted behavior. Main effects of SNR were found for both electrophysiology and speech perception measures, while signal level effects were found generally only for speech testing. These results demonstrate that when signals are presented in noise, sensitivity to SNR cues obscures any encoding of signal level cues. Electrophysiology and behavioral measures were strongly correlated. The best physiological predictors (e.g., latency, amplitude, and area of CAEP waves) of behavior (SNR at which 50 % of the sentence is understood) were N1 latency and N1 amplitude measures. In addition, behavior was best predicted by the 70-dB signal/5-dB SNR CAEP condition. It will be important in future studies to determine the relationship of electrophysiology and behavior in populations who experience difficulty understanding speech in noise such as those with hearing impairment or age-related deficits.     

听皮层认知功能障碍与听力损失相关性的探讨

听力损失(hearing loss,HL)和认知功能(cognitive function,CF)有着密切的关系.耳蜗是听觉信息传入和传出的重要结构,即中枢听觉系统接收和反馈听觉信息的重要窗口.耳蜗精细结构就具有言语编码的功能,耳蜗的基底膜(basal membrane,BM)和毛细胞(hair cells,HCs)从...     

听觉剥夺后大鼠听皮层神经元的形态学变化和SHP-2基因的表达

目的研究双侧耳蜗毁损后大鼠听皮层神经元细胞的形态学变化和蛋白酪氨酸磷酸酶2型（src-homology domain containing protein tygosine phosphatase type 2,SHP -2）基因的表达。方法选取SD大鼠48只,随机分为4个实验组（2周组、4周组、6周组、8周组）和4个相应的对照组,每组6只。实验组动物行双侧耳蜗损毁术,通过HE染色和Nissl染色观察听皮层神经元细胞的形态学变化,用RT -PCR技术检测各组听皮层神经元细胞的SHP-2基因的表达,行相对定量分析。结果 HE染色和Nissl染色可见各实验组大鼠听皮层神经元细胞的凋亡形态随时间延长而加重,呈多样化表现;各对照组大鼠听皮层细胞形态正常。实验2、4、6、8周组SHP-2基因的RT -PCR相对表达量分别为1．1±0．28、1．5±0．04、2．5±0．08、11．0±0．06,随时间延长呈上升趋势,各实验组之间差异均有统计学意义（P＜0．05）。结论听觉剥夺可导致听皮层神经元细胞凋亡,凋亡的程度随时间延长逐渐加重;SHP-2基因可促进听皮层神经元细胞的增生,增生的程度也随时间延长而加重;在这两个相互拮抗的因素中,凋亡是最终的结果。     

Physiological Evidence for a Midline Spatial Channel in Human Auditory Cortex

Studies with humans and other mammals have provided support for a two-channel representation of horizontal (“azimuthal”) space in the auditory system. In this representation, location-sensitive neurons contribute activity to one of two broadly tuned channels whose responses are compared to derive an estimate of sound-source location. One channel is maximally responsive to sounds towards the left and the other to sounds towards the right. However, recent psychophysical studies of humans, and physiological studies of other mammals, point to the presence of an additional channel, maximally responsive to the midline. In this study, we used electroencephalography to seek physiological evidence for such a midline channel in humans. We measured neural responses to probe stimuli presented from straight ahead (0 °) or towards the right (+30 ° or +90 °). Probes were preceded by adapter stimuli to temporarily suppress channel activity. Adapters came from 0 ° or alternated between left and right (?30 ° and +30 ° or ?90 ° and +90 °). For the +90 ° probe, to which the right-tuned channel would respond most strongly, both accounts predict greatest adaptation when the adapters are at ±90 °. For the 0 ° probe, the two-channel account predicts greatest adaptation from the ±90 ° adapters, while the three-channel account predicts greatest adaptation when the adapters are at 0 ° because these adapters stimulate the midline-tuned channel which responds most strongly to the 0 ° probe. The results were consistent with the three-channel account. In addition, a computational implementation of the three-channel account fitted the probe response sizes well, explaining 93 % of the variance about the mean, whereas a two-channel implementation produced a poor fit and explained only 61 % of the variance.     

Slow Cortical Evoked Potentials: Interactions of Auditory,Vibro-Tactile and Shock Stimuli

An interaction experiment, in which stimuli of one kind were interposed between stimuli of another variety, was performed on 6 subjects with 8 replications. Cortical vertex potentials evoked by shocks to the median nerve, by vibrotactile stimulation of a finger or by 2400 Hz filtered clicks were averaged by a computer. The inter-stimulus interval was 5 sec. Then stimuli of two different kinds were presented alternately at 2.5 sec intervals. The responses for each kind were averaged separately. The amplitudes, measured from N₁ to P₂, were compared for all combinations of the three modalities.

Cross-modality depression of response occurred (10% level of confidence) for tactile responses with interposed auditory stimuli and (1 % level of confidence) for shock responses with interposed tactile stimuli. A general trend toward depression was clear, with an overall average of 15%, although it was not consistent for all subjects or symmetrical among types of stimuli. This compares with 28% depression when the inter-stimulus interval for identical stimuli was reduced from 5 sec to 2.5 sec.

Resume

Une expérience d'interactions, dans laquelle des stimuli d'un certain mode sensoriel étaient intercalés entre des stimuli d'un mode différent, a été effectuée sur six sujets avec huit répétitions. Un appareil à mémoires magnétiques a calculé les moyennes des potentiels corticaux du vertex, évoqués par des chocs appliqués sur le nerf médian, par une stimulation vibro-tactile d'un doigt ou par des clicks filtrés de 2 400 Hz. L'intervalle entre les stimuli successifs était de 5 secondes. Par la suite, les stimuli de deux modes différents alternaient en intervalles de 2,5 secondes. Les moyennes de réponses pour chacun de ces modes étaient séparemment calculées. Les amplitudes, mesurées de N₁ à P₂, étaient comparées dans toutes les combinaisons des trois modalités.

Une diminution transmodale de réponses se produisait pour les réponses tactiles avec des stimuli auditifs intercalés (significatif à un niveau de 10%) et pour des réponses aux chocs avec des stimuli tactiles intercalés (significatif à un niveau de 1%). Une tendance générate de diminution, ayant une grande moyenne de 15%, se manifestait clairement, bien qu'elle n'aie été soutenue par tous les sujets et ne s'avéraˇt pas symétrique parmi les types de stimuli. Par contre, en réduisant l'intervalle entre les stimuli successifs de 5 à 2,5 secondes, le taux de diminution était de 28%.     

皮层听觉诱发电位评估耳聋儿童助听器验配效果的意义

目的 探讨皮层听觉诱发电位(cortical auditory evoked potential,CAEP)在助听器验配效果评估中的应用价值,为临床耳聋儿童听觉言语康复效果评估提供参考.方法 26例语前聋患儿均双耳选配助听器,分别测试患儿助听条件下的CAEP及助听听阈;根据助听后三个刺激声/m/、/g/、/t/在55 dB SPL强度下是否全部引出波形将息儿分为A组和B组,全部引出波形的患儿为A组,其余患儿为B组,比较二组的助听听阈.结果 26例患儿CAEP波形引出率为96.15％(25/26),A组(11例)0.25、0.5、1、2、4 kHz助听听阈均值分别为32.73±7.54、27.27±5.18、35.00±5.48、35.91±7.35、35.45±4.72 dB HL;B组(15例),除1例未引出CAEP外,有9例在65 dB SPL强度下全部引出CAEP波形,其0.25～4 kHz各频率助听听阈均值分别为36.11±7.82、35.00±4.33、38.89±6.51、40.00±7.07、43.33±8.66 dB HL;有5例在75 dB SPL强度下全部引出CAEP波形,其0.25～4 kHz各频率助听听阈均值分别为44.00±12.94、39.00±7.41、49.00±6.52、44.00±6.52、54.00±11.94 dBHL,且A组患儿各刺激声对应频段助听听阈均低于B组,差异有统计学意义(P＜0.05).阈值强度下低频声/m/、中频声/g/、高频声/t/的P1波潜伏期均值分别为130.16±24.85、114.80±25.99、122.88±27.05 ms,幅值分别为6.58±4.53、6.41±3.97、5.58±3.56 μV,相应频段助听听阈分别为34.30±7.69、40.20±8.48、41.40±8.07 dBHL,P1波潜伏期与相应频段助听听阈均无显著相关(P＞0.05),P1波幅值与相应频段助听听阈呈显著负相关(P＜0.05).结论 CAEP测试可用于评估儿童助听器选配效果,55 dB SPL强度下能够引出CAEP波形可作为评估助听器选配效果良好的指标之一.     

Effects of Spectral Degradation on Attentional Modulation of Cortical Auditory Responses to Continuous Speech

This study investigates the effect of spectral degradation on cortical speech encoding in complex auditory scenes. Young normal-hearing listeners were simultaneously presented with two speech streams and were instructed to attend to only one of them. The speech mixtures were subjected to noise-channel vocoding to preserve the temporal envelope and degrade the spectral information of speech. Each subject was tested with five spectral resolution conditions (unprocessed speech, 64-, 32-, 16-, and 8-channel vocoder conditions) and two target-to-masker ratio (TMR) conditions (3 and 0 dB). Ongoing electroencephalographic (EEG) responses and speech comprehension were measured in each spectral and TMR condition for each subject. Neural tracking of each speech stream was characterized by cross-correlating the EEG responses with the envelope of each of the simultaneous speech streams at different time lags. Results showed that spectral degradation and TMR both significantly influenced how top-down attention modulated the EEG responses to the attended and unattended speech. That is, the EEG responses to the attended and unattended speech streams differed more for the higher (unprocessed, 64 ch, and 32 ch) than the lower (16 and 8 ch) spectral resolution conditions, as well as for the higher (3 dB) than the lower TMR (0 dB) condition. The magnitude of differential neural modulation responses to the attended and unattended speech streams significantly correlated with speech comprehension scores. These results suggest that severe spectral degradation and low TMR hinder speech stream segregation, making it difficult to employ top-down attention to differentially process different speech streams.     

脉冲激光刺激听神经机制的研究进展

鉴于电刺激听神经产生听觉的局限性,激光刺激诱发神经冲动近来逐渐成为研究热点,激光刺激听神经可能机制为光声效应、光热效应及激光辐射后细胞膜一系列改变,但是由于其具体机制较为复杂,仍不是十分清楚,值得进一步研究。本文并对扩大刺激参数范围、多通道研究、开展临床实验、光电联合刺激及光遗传学技术等方面进行了展望。     

Illusions in rhinoplasty.

A good rhinoplasty surgeon attempts to enhance nasal performance through airway and appearance improvement. The great rhinoplasty surgeon routinely improves not only nasal performance but endeavors to achieve a higher level of overall facial aesthetic enhancement by manipulating the surgical illusions of the face. This cohesive interplay of science between the eyes, cheeks, nose, lips, and chin is known all to well by the master facial plastic surgeon who defines the art of rhinoplasty.     

Auditory Cortical Activity During Cochlear Implant-Mediated Perception of Spoken Language, Melody, and Rhythm

Despite the significant advances in language perception for cochlear implant (CI) recipients, music perception continues to be a major challenge for implant-mediated listening. Our understanding of the neural mechanisms that underlie successful implant listening remains limited. To our knowledge, this study represents the first neuroimaging investigation of music perception in CI users, with the hypothesis that CI subjects would demonstrate greater auditory cortical activation than normal hearing controls. H₂ ¹⁵O positron emission tomography (PET) was used here to assess auditory cortical activation patterns in ten postlingually deafened CI patients and ten normal hearing control subjects. Subjects were presented with language, melody, and rhythm tasks during scanning. Our results show significant auditory cortical activation in implant subjects in comparison to control subjects for language, melody, and rhythm. The greatest activity in CI users compared to controls was seen for language tasks, which is thought to reflect both implant and neural specializations for language processing. For musical stimuli, PET scanning revealed significantly greater activation during rhythm perception in CI subjects (compared to control subjects), and the least activation during melody perception, which was the most difficult task for CI users. These results may suggest a possible relationship between auditory performance and degree of auditory cortical activation in implant recipients that deserves further study.     

Altered Cortical Activity in Prelingually Deafened Cochlear Implant Users Following Long Periods of Auditory Deprivation

Auditory stimulation during childhood is critical for the development of the auditory cortex in humans and with that for hearing in adulthood. Age-related changes in morphology and peak latencies of the cortical auditory evoked potential (CAEP) have led to the use of this cortical response as a biomarker of auditory cortical maturation including studies of cortical development after deafness and subsequent cochlear implantation. To date, it is unknown whether prelingually deaf adults, with early onset deafness (before the age of 2 years) and who received a cochlear implant (CI) only during adulthood, would display absent or aberrant CAEP waveforms as predicted from CAEP studies in late implanted prelingually deaf children. In the current study, CAEP waveforms were recorded in response to electric stimuli in prelingually deaf adults, who received their CI after the age of 21 years. Waveform morphology and peak latencies were compared to the CAEP responses obtained in postlingually deaf adults, who became deaf after the age of 16. Unexpectedly, typical CAEP waveforms with adult-like P1-N1-P2 morphology could be recorded in the prelingually deaf adult CI users. On visual inspection, waveform morphology was comparable to the CAEP waveforms recorded in the postlingually deaf CI users. Interestingly, however, latencies of the N1 peak were significantly shorter and amplitudes were significantly larger in the prelingual group than in the postlingual group. The presence of the CAEP together with an early and large N1 peak might represent activation of the more innate and less complex components of the auditory cortex of the prelingually deaf CI user, whereas the CAEP in postlingually deaf CI users might reflect activation of the mature neural network still present in these patients. The CAEPs may therefore be helpful in the assessment of developmental state of the auditory cortex.     

Cortical Auditory Evoked Potentials in Response to Frequency Changes with Varied Magnitude,Rate, and Direction

Recent literature on cortical auditory evoked potentials has focused on correlations with hearing performance with the aim to develop an objective clinical tool. However, cortical responses depend on the type of stimulus and choice of stimulus parameters. This study investigates cortical auditory evoked potentials to sound changes, so-called acoustic change complexes (ACC), and the effects of varying three stimulus parameters. In twelve normal-hearing subjects, ACC waveforms were evoked by presenting frequency changes with varying magnitude, rate, and direction. The N1 amplitude and latency were strongly affected by magnitude, which is known from the literature. Importantly, both of these N1 variables were also significantly affected by both rate and direction of the frequency change. Larger and earlier N1 peaks were evoked by increasing the magnitude and rate of the frequency change and with downward rather than upward direction of the frequency change. The P2 amplitude increased with magnitude and depended, to a lesser extent, on rate of the frequency change while direction had no effect on this peak. The N1–P2 interval was not affected by any of the stimulus parameters. In conclusion, the ACC is most strongly affected by magnitude and also substantially by rate and direction of the change. These stimulus dependencies should be considered in choosing stimuli for ACCs as objective clinical measure of hearing performance.

     

听力损失老年人佩戴助听器前后皮层听觉诱发电位与言语感知的研究

目的 探讨皮层听觉诱发电位(cortical auditory evoked potential,CAEP)用于中度与重度听力损失老年人助听前后言语识别能力评估的可靠性和有效性.方法 26例中度与重度听力损失老年人均验配同一型号测试用助听器,于佩戴助听器前后在声场中分别测试/m/、/g/、/t/三个刺激声在65 dB ...     

听障儿童听觉分辨能力训练

听觉分辨能力训练的目的在于提高听力障碍者准确而快速地分辨声音是否相同的能力,该阶段是大脑真正认识声音,学会比较的开始。听觉分辨能力训练包括综合分辨和精细分辨两部分。本文介绍了听觉分辨能力训练的内容与方法,并以1名听障儿童听觉分辨能力训练的个别化教育康复方案为例,阐释临床听觉分辨能力的训练。     

听觉神经系统中的髓鞘相关病理和可塑性机制研究进展

髓鞘是高等脊椎动物中实现快速、精准神经信号传递的重要结构,是形成和维持神经元网络之间快速、协调交流的关键组成部分,其对于听觉神经功能的正常运行起到了重要作用。近些年来,学术界越来越意识到,髓鞘的动态变化是听觉神经元系统病理和可塑性机制中重要环节。本文旨在通过回顾中枢和周围听觉系统中的髓鞘相关病理机制,同时综述听觉活动、脑源性神经营养因子BDNF、ERK1/2信号通路、髓鞘相关抑制因子Nogo-A等因素与听觉神经系统髓鞘可塑性之间的关系。     

Auditory Training with Spectrally Shifted Speech: Implications for Cochlear Implant Patient Auditory Rehabilitation

After implantation, postlingually deafened cochlear implant (CI) patients must adapt to both spectrally reduced and spectrally shifted speech, due to the limited number of electrodes and the limited length of the electrode array. This adaptation generally occurs during the first three to six months of implant use and may continue for many years. To see whether moderate speech training can accelerate this learning process, 16 naïve, normal-hearing listeners were trained with spectrally shifted speech via an eight-channel acoustic simulation of CI speech processing. Baseline vowel and consonant recognition was measured for both spectrally shifted and unshifted speech. Short daily training sessions were conducted over five consecutive days, using four different protocols. For the test-only protocol, no improvement was seen over the five-day period. Similarly, sentence training provided little benefit for vowel recognition. However, after five days of targeted phoneme training, subjects’ recognition of spectrally shifted vowels significantly improved in most subjects. This improvement did not generalize to the spectrally unshifted vowel and consonant tokens, suggesting that subjects adapted to the specific spectral shift, rather than to the eight-channel processing in general. Interestingly, significant improvement was also observed for the recognition of spectrally shifted consonants. The largest improvement was observed with targeted vowel contrast training, which did not include any explicit consonant training. These results suggest that targeted phoneme training can accelerate adaptation to spectrally shifted speech. Given these results with normal-hearing listeners, auditory rehabilitation tools that provide targeted phoneme training may be effective in improving the speech recognition performance of adult CI users.