耳蜗圆窗记录的蜗神经同步放电活动

目的:探讨豚鼠耳蜗神经活动频谱(ASECA)1kHz处出现的特征谱峰(简称ASECA-1kHz)的起源及其与听神经放电活动的关系。方法:采用不同刺激声在同侧及对侧刺激条件下记录清醒豚鼠ASECA-1kHz的改变。结果:(1)中心频率高于8kHz,且强度低于其耳间衰减值的窄带噪声进行对侧声刺激则导致ASECA-1kHz幅值下降;(2)带宽高于或低于1.5kHz的同侧噪声刺激引起ASECA-1kHz相应地增加或降低;(3)对侧纯音刺激(强度不大于耳间衰减值)对ASECA不产生影响,但频率高于4kHz的同侧纯音刺激引起ASECA-1kHz下降。此外,声刺激引起的ASECA-1kHz改变的时程图与Kiang等所记录的听神经纤维对声刺激反应的直方图非常相似。结论:豚鼠ASECA-1kHz起源于耳蜗基底周对高频声响应的有限投射区域(12.5-25kHz),且代表该区域内听神经纤维的同步自发放电活动。     

人工耳蜗用电极

耳蜗电极是人工耳蜗中的一个重要组成部份,外界声音信号经刺激器转换成电信号后经电极传至听神经纤维使耳聋患者获得音感。耳蜗电极在材料的选择,结构形式和制作方法上有着特殊的要求。本文就人工耳蜗电极的金属材料,绝缘材料和载体材料的选择以及在生物体内的稳定性作了简要的探讨。此外,对不同类型的电极结合不同的手术途径作了分析。我们制作的耳蜗电极经过扫描电镜,绝缘耐压,阻抗等方面的测试以及动物实验的结果     

50例正常人脑干三叉神经诱发电位分析

目的：探讨无伤害性刺激脑干三叉诱发电位(BTEP)的检测方法和波形特征。方法：对50名健康志愿者进行上唇电脉冲刺激,用远场记录法在头皮上记录刺激后10 ms内出现的反应波,寻找最适宜的刺激和记录参数。部分被试者同时进行脑干听觉诱发电位(BAEP)和正中神经短潜伏期体感诱发电位(SEP)检测。结果：50例正常人均记录到满意的BTEP反应波,其峰潜伏期、波间期值与文献资料近似。BTEP的脑干成分较BAEP和SSEP清晰、明确。结论：用无伤害刺激在正常人可以记录到清晰、稳定的BTEP反应波。BTEP为评价三叉神经周围结构和脑干中枢通路提供了新的、可靠的电生理学方法,是研究脑干功能的又一指标。     

在体记录大鼠海马神经元对不同单色激光闪光刺激的反应

目的:探讨海马CA1锥体神经元对不同单色激光闪光刺激的反应,为论证激光诱发的神经系统生物学效应提供实验支持。方法:健康成年SD大鼠麻醉后,行气管插管术,开颅钻孔暴露脑面,进行在体膜片钳记录。全细胞记录稳定后,采用4种不同波长的单色激光对其眼球进行闪光刺激,记录大鼠海马神经元的反应。结果:给予大鼠闪光刺激后,其海马神经元对蓝色激光和紫色激光表现出明显的超极化反应,对红色和绿色激光刺激则没有明显的反应。蓝光引起的变化中,超极化的幅值为(8.32±1.10)m V,反应持续时间为(115.32±13.02)ms;紫光引起的超极化的幅值为(9.01±2.25)m V,刺激反应持续时间为(109.27±16.62)ms,蓝光和紫光之间没有统计学差异。50 m W、75 m W、100 m W、125 m W功率的紫色激光刺激引起的超极化幅值,分别为(7.28±0.16)m V、(9.25±0.71)m V、(10.91±0.08)m V、(12.67±0.38)m V,相关性分析显示幅值变化与刺激功率高度正相关。结论:麻醉状态下,蓝光和紫色的闪光刺激可以诱导大鼠海马神经元出现明确的抑制性反应,红光和绿光没有明显的作用。     

电刺激人耳蜗的诱发电位

以往对人工耳蜗装置的评价主要依靠患者的主观感觉及行为反应。为了建立有助于分析患者植入人工耳蜗后听觉功能恢复情况的客观指标,并用以确定电刺激激活耳蜗听神经纤维、中枢听觉通路以及大脑皮层听区的效应,进而比较电刺激与声刺激两类诱发电活动的生理学性质,我们观察了五例鼓阶电极植入者对电刺激耳蜗所产生的脑干及皮层等部位的诱发电活动。诱发电位经数字平均器进行叠加。电刺激耳蜗诱发的脑干电位一般只有波Ⅲ与波V能够清楚显示,潜伏期均值分别为2.07与3.89毫秒,较声刺激引起者缩短约2毫秒。皮层诱发电位的主要特征是由峰潜伏期43毫秒的正波和86毫秒的负波构成的一组电位,与声诱发者类似。声刺激经人工耳蜗装置后引出的诱发电位结果与直接耳蜗电刺激者相符。诱发电位的出现与患者的主观声感大体一致。     

听觉神经电刺激:在体直流测量

神经修复应用电荷恢复机理可以确保电刺激的电荷均衡。核耳蜗植入（Ｎｕｃｌｅｕｓｃｏ－ｃｈｌｅａｒｉｍｐｌａｎｔｓ）技术在脉冲间期将所有刺激电极短路,以实现电荷平衡,导致一个小剩余直流电的出现。本文试图用不同的电荷恢复机理、不同的刺激模式和不同的刺激参数研究剩余ＤＣ的特性,并通过建模得到对该技术的根本认识。对６只重６００ｇ～１２００ｇ的健康豚鼠,我们用ＮｕｃｌｅｕｓＣＩ２４Ｍ耳蜗植入进行刺激,在的四个耳蜗内铂电极上测量ＤＣ。采用中高脉冲率（１２００～１４５００ｐｕｌｓｅｓ／ｓ）和刺激强度（０．２１～…     

电子耳蜗CIS语音信号处理方案的计算机仿真及声音合成

电子耳蜗是用有限个电极刺激听神经以恢复全聋人听觉的装置,本利用耳蜗的电刺激简化在模型,在计算机上对连续交替取样（ｃｏｎｔｉｎｕｅｄｉｎｔｅｒｌｅａｖｅｄｓａｍｐｌｉｎｇ,简称ＣＩＳ）方案进行了仿真及声音合成,以模拟耳蜗植入者感受的声音,仿真方法和结果对研究语音信号处理的新方案及临床参数选择具有一定的意义。     

大鼠三叉神经诱发电位检测方法的研究

目的 获得较佳的大鼠三叉神经诱发电位检测方法。方法 使用多导诱发电位仪在不同刺激及不同导联记录方法下检测大鼠三又神经诱发电位。结果 0．04ms波宽的电脉冲刺激和Cz-Cv7导联方法记录时，大鼠三叉神经诱发电位各导联波形重合较好，各波检出率均较高，潜伏期的标准差较小。结论 采用0.04ms渡宽电脉冲刺激和Cz-Cv7导联方法记录的大鼠三叉神经诱发电位较佳。     

电子耳蜗植入术后麻醉恢复室护理体会

<正>近年来随着生物医学工程等高新技术的出现,电子耳蜗是至今为止让全聋患儿回到有声世界的唯一有效的方法,其原理是利用植入内耳的电极,绕过内耳受损的部分,用电流直接刺激听神经,使患儿获得听力[1]。我科麻醉恢复室自2012年8月至2013年1月,共收治电子耳蜗术后患者33例,均为青春期以前     

豚鼠颅顶频率跟随反应和微音器电位的观察

频率跟随反应(FFR)是听觉系统对持续音刺激的电反应,其特点是反应的波峰间隔与声刺激的周期相同,并持续出现于刺激期内。本文目的是了解豚鼠颅顶FFR的特征及其与耳蜗微音器电位(CM)的鉴别。 实验共用豚鼠15只,体重300～505克,在Nembutal麻醉下进行。记录电极为直径0.45mm的金属小球,置于颅顶头皮。参考电极接插入口中的金属棒。用7Sl1     

Time course of simultaneous masking in the starling’s auditory forebrain

 Simultaneous masking of pure tones was studied in the primary auditory forebrain of a songbird species, the European starling (Sturnus vulgaris). The responses of 32 multi-unit clusters in the input layer of the auditory neostriatum (field L2a) were recorded via radiotelemetry from freely moving birds. The probe was a 10-ms tone burst at the units’ characteristic-frequency (CF) presented 20 dB above the threshold. The masker was an 80-ms tone burst presented either at the units’ CF (excitatory masker) or at a frequency located in inhibitory side-bands (inhibitory masker) of the units’ tuning curves. The probe was presented either 3 ms or 63 ms after masker onset. Probes presented at a 3-ms delay were influenced at significantly lower levels of an excitatory masker than probes presented at a 63-ms delay. The mean difference in masker level at the detection thresholds for both probe delays was 8 dB. No difference in masker level was observed for inhibitory-frequency maskers. The observed neural masking effects may be explained by at least four mechanisms: (1) swamping of the probe response by the response to the masker, (2) a reduction of the probe response during neural adaptation of the response to the masker, (3) a reduction of the probe response during side-band inhibition in the central nervous system, and (4) suppression originating in the cochlea. Received: 20 April 1998 / Accepted: 16 September 1998     

Development of functional synaptic connections in the auditory system visualized with optical recording: afferent-evoked activity is present from early stages

A comprehensive survey of auditory network formation was performed in the brain stem of the chicken embryo using voltage-sensitive dye recording. Intact medulla/brain stem preparations with the auditory branch of the eighth nerve attached were dissected from 5.5- to 8-day chicken embryos, and responses evoked by nerve stimulation were recorded optically. In the medulla of 7- and 8-day embryos, we identified four response areas, corresponding to ipsilateral Nucleus magnocellularis (NM) and Nucleus angularis (NA), which receive the auditory afferents, and ipsi- and contralateral Nucleus laminaris (NL), which receive projections from NM. The optical responses consisted of a fast spikelike signal followed by a long-lasting slow signal, which reflected the sodium-dependent action potential and glutamatergic excitatory postsynaptic potential (EPSP), respectively. In NM, NA, and NL, the EPSP-related slow optical signals were detected from some 6-day and all 7- and 8-day preparations, indicating that functional synaptic connectivity in these nuclei arises by the 7-day stage. In the pons of 7- and 8-day embryos, we identified two additional response areas, which evidently correspond to ipsi- and contralateral Nucleus lemnisci lateralis (NLL), the higher-order nuclei of the auditory pathway. Furthermore, we detected optical responses from the contralateral cerebellum, which possibly correspond to transient projections observed only during embryogenesis. The present study demonstrates that functional auditory circuits are established in the chicken embryo at stages earlier than previously reported. We discuss the possible role of afferent-evoked activity with reference to auditory neural network formation.     

Neural mechanisms of tone-on-tone masking: patterns of discharge rate and discharge synchrony related to rates of spontaneous discharge in the chinchilla auditory nerve

Responses of chinchilla auditory nerve fibers to brief probe tones in the presence of a fixed tonal masker were obtained. The stimulus conditions were analogous to those that have been used in many psychophysical experiments. The relation between previously described response properties of auditory nerve fibers and features of psychophysical tone-on-tone masking was examined. In psychophysical studies, a fixed narrowband masker produces a characteristic pattern of masked thresholds, which becomes broad and asymmetrical at high masker levels. In the present experiment 1, a 5,000-Hz masker was presented at 30, 50, and 70 dB SPL. Masked thresholds based on the average rate of response to probe tones were estimated for single auditory nerve fibers. The lowest of these masked thresholds formed a pattern similar to the psychophysical masking pattern, becoming broader and more asymmetrical as the masker was increased to 70 dB SPL. The masked thresholds of fibers with low and medium rates of spontaneous discharge (SR) were as low as or lower than the masked thresholds of fibers with high SRs. In certain frequency regions, masked thresholds based on responses to cochlear distortion products were lower than the masked thresholds of any fiber responding to the probe tone; this result is also similar to previous psychophysical observations. In experiment 2, responses of chinchilla auditory nerve fibers to probe tones in the presence of a masker at 1,000 Hz and 50 dB SPL were studied. Probe tone thresholds in the presence of this masker have been measured psychophysically in chinchillas. Thus the relation between behavioral and neural masked thresholds in the same species could be examined. Masked thresholds were estimated from average discharge rate responses and also from discharge synchrony. Good quantitative agreement was observed between the probe tone levels at which changes in average discharge rate were observed and the chinchilla's behavioral masked thresholds. For fibers matched for characteristic frequency, the masked thresholds based on average discharge rate of high-SR fibers tended to be elevated compared with the thresholds of medium-SR fibers. Changes in discharge rate synchronized to the probe tone occurred at levels lower than the chinchilla's behavioral masked thresholds. If discharge synchrony can be used for detection, the code would appear to be based on the relative synchrony to the probe tone and to the masking tone. Low synchrony masked thresholds were obtained from fibers with all SRs.(ABSTRACT TRUNCATED AT 400 WORDS)     

Brainstem frequency-following response and simple motor reaction time.

Simple motor reaction times (RT) in humans show marked trial-to-trial variations. In the present study, a brief tone (400 Hz, 37.5 ms duration) that was the imperative stimulus in a RT paradigm evoked the brainstem frequency-following response (FFR). Horizontal and vertical montage FFRs were recorded to evaluate neural responses with putative origins in auditory nerve and central brainstem, respectively. The main question concerned the possible relationship between trial-to-trial variations in RT speed and FFR response properties. The results showed a reliable pattern in which fast RT trials yielded larger amplitudes (relative to slow trials) in earlier milliseconds of the FFR, and slow RT trials yielded relatively larger amplitudes in later milliseconds of the response. These results support the conclusion that early processing in the auditory brainstem is not automatic and invariant. Rather, short-latency evoked potentials appear to reflect trial-to-trial variations related to events far removed from the first synapse of sensory coding, perhaps depending upon cortically mediated influences such as cognition or attention.     

Representation of auditory-filter phase characteristics in the cortex of human listeners

Harmonic tone complexes with component phases, adjusted using a variant of a method proposed by Schroeder, can produce pure-tone masked thresholds differing by >20 dB. This phenomenon has been qualitatively explained by the phase characteristics of the auditory filters on the basilar membrane, which differently affect the flat envelopes of the Schroeder-phase maskers. We examined the influence of auditory-filter phase characteristics on the neural representation in the auditory cortex by investigating cortical auditory evoked fields (AEFs). We found that the P1m component exhibited larger amplitudes when a long-duration tone was presented in a repeating linearly downward sweeping (Schroeder positive, or m(+)) masker than in a repeating linearly upward sweeping (Schroeder negative, or m(-)) masker. We also examined the neural representation of short-duration tone pulses presented at different temporal positions within a single period of three maskers differing in their component phases (m(+), m(-), and sine phase m(0)). The P1m amplitude varied with the position of the tone pulse in the masker and depended strongly on the masker waveform. The neuromagnetic results in all cases were consistent with the perceptual data obtained with the same stimuli and with results from simulations of neural activity at the output of cochlear preprocessing. These findings demonstrate that phase effects in peripheral auditory processing are accurately reflected up to the level of the auditory cortex.     

Effects of stimulus intensity and duration on photoresponses of single rods in the frog retina

Electrical responses to light flashes were recorded from single red rods in dark-adapted retinas of the bullfrog, Rana catesbeiana. When the flashes were less than or equal to 50 ms in duration, plots of the peak amplitude of the responses as a function of log stimulus intensity were found to be parallel, and the stimulus intensity and duration required to elicit criterion-amplitude responses showed a linear relation with a negative unit slope. Furthermore the waveforms of equal-amplitude responses to flashes of different intensities and durations were superimposable. With increases in the stimulus duration beyond 50 ms, however, the slopes of the response-log intensity curves for the higher stimulus intensities decreased, the slope of curves describing the intensity required to elicit criterion responses became less negative, and the responses of the rods decayed more slowly. These results indicate that within 50 ms after the onset of flash stimuli, the effect of incident photons summate linearly to evoke rod responses of certain sub-saturating amplitudes when assessed in terms of the peak response amplitude as well as the response waveform.     

Non-linearity of skin resistance response to intraneural electrical stimulation of sudomotor nerves.

Intraneural electrical stimuli (0.3 mA, 0.2 ms) were delivered via a tungsten microelectrode inserted into a cutaneous fascicle in the median nerve at the wrist in 16 normal subjects, and the effects on the sweat glands within the innervation zone were recorded as changes of skin resistance. In order to examine the relationship between the skin resistance level and the amplitude of transient resistance responses, trains of high frequency stimulation were used to reduce the skin resistance level and then transient resistance responses were evoked by single stimuli at 0.1 Hz. Regional anaesthesia of the brachial plexus in the axilla eliminated spontaneous sympathetic activity and reflex effects. At high skin resistance levels response amplitudes to single stimuli were low but they increased successively to a maximum at intermediate levels and then decreased again at low resistance levels. Repeated stimulation sequences evoked qualitatively similar response curves but quantitatively both response amplitudes and skin resistance levels were slightly reduced upon repetition. We suggest that the changes of response amplitudes are due to variable resistivity of the corneal layer. The shifts of the response curves with repetition of stimulation may result from increased hydration of the corneum. It is concluded that the variability of response amplitudes to constant stimuli makes the amplitude of a skin resistance response unsuitable as an indicator of the strength of sympathetic sudomotor nerve traffic.     

Non-linearity of skin resistance response to intraneural electrical stimulation of sudomotor nerves

Intraneural electrical stimuli (0.3 mA, 0.2 ms) were delivered via a tungsten micro-electrode inserted into a cutaneous fascicle in the median nerve at the wrist in 16 normal subjects, and the effects on the sweat glands within the innervation zone were recorded as changes of skin resistance. In order to examine the relationship between the skin resistance level and the amplitude of transient resistance responses, trains of high frequency stimulation were used to reduce the skin resistance level and then transient resistance responses were evoked by single stimuli at 0.1 Hz. Regional anaesthesia of the brachial plexus in the axilla eliminated spontaneous sympathetic activity and reflex effects. At high skin resistance levels response amplitudes to single stimuli were low but they increased successively to a maximum at intermediate levels and then decreased again at low resistance levels. Repeated stimulation sequences evoked qualitatively similar response curves but quantitatively both response amplitudes and skin resistance levels were slightly reduced upon repetition. We suggest that the changes of response amplitudes are due to variable resistivity of the corneal layer. The shifts of the response curves with repetition of stimulation may result from increased hydration of the corneum. It is concluded that the variability of response amplitudes to constant stimuli makes the amplitude of a skin resistance response unsuitable as an indicator of the strength of sympathetic sudomotor nerve traffic.     

Trajectory control in targeted force impulses

Summary This study was undertaken in order to determine the time course of the process by which information derived from a visual target is used to accurately set the amplitude of a simple motor response. We refer to this process as response specification. Separate auditory and visual cues were given to the subjects in order to independently control the moment of response initiation and the time available for processing amplitude information from the target. Six subjects initiated impulses of isometric force in synchrony with the last of predictable series of regular tones. Response amplitudes were to match one of three visual target steps occurring at random times between 0 and 400 ms before the response-synchronizing tone. Using these separate auditory and visual cues, we were able to systematically vary the time interval between target presentation and response onset, termed here Stimulus-Response or S-R interval. Target steps were presented in blocks of either predictable (simple condition) or unpredictable (choice condition) amplitudes. The peak forces and the peaks of their time derivatives were analyzed to determine how subjects achieved accuracy under the different conditions and at different S-R intervals. The trajectories of responses produced in the simple condition were independent of the S-R interval. In contrast, when targets were presented in unpredictable order, the distribution of the peak forces of the subjects' responses depended on the S-R interval. At short S-R intervals (<125 ms), subjects made responses whose peak forces were distributed around the center of the range of target steps. These responses formed a unimodal, but broad distribution which was independent of actual target amplitude. With increasing S-R interval (>125 ms), the distributions of peak forces gradually shifted toward the correct target amplitudes, with the means reaching the appropriate amplitudes at S-R intervals of 250–400 ms. At S-R intervals comparable to a reaction time, the range of peak forces was constricted to a similar extent as previously observed in a reaction time task (Hening et al. 1988). We found that the gradual improvement of accuracy was not achieved through changes in trajectory control: at all S-R intervals, subjects utilized a pulse-height control policy (Gordon and Ghez 1987a). Different peak forces were achieved by varying the rate of rise of force, while force rise time was held relatively invariant. We did find, however, that within the constraints imposed by rise time regulation, compensatory adjustments to the force trajectories (Gordon and Ghez 1987b) were greatest during the period of specification. We conclude that (1) subjects can initiate their responses independent of the degree of specification achieved and that the normal process of specification of amplitude begins earlier and continues longer than the latency of responses in a reaction time task; (2) before target presentation, subjects prepare a default response whose amplitude is biased by prior experience with the targets presented in the task. We hypothesize that the central mechanisms that specify response amplitude do so by a progressive adjustment of the default parameters.     

Prepulse modulation of the startle reaction and the blink reflex in normal human subjects

Blink reflexes are usually considered the most representative and consistent response of the auditory startle reaction (ASR), and they are often the only response evaluated in human psychophysiological studies. However, auditory stimuli also induce an auditory blink reflex (ABR), the physiological characteristics and brainstem circuitry of which may be different from those of the ASR. This study aimed to investigate whether there were differences between the orbicularis oculi (OOc) responses elicited with the ABR (OOcABR) and those elicited with the ASR (OOcASR) regarding their behavior to prepulse modulation. For comparison, we also examined the OOc responses to supraorbital nerve stimulation (OOcEBR). Electromyographic responses were simultaneously recorded from the OOc, masseter (MAS) and sternocleidomastoid (SCM) muscles. ABRs were considered when auditory stimuli induced responses limited to the OOc, and ASRs were considered when responses were induced in all muscles recorded from. Prepulse stimuli were either a weak electrical stimulation at the third finger (somatosensory prepulse) or a weak acoustic tone (auditory prepulse) that preceded the response-eliciting stimuli by intervals ranging from 0 to 200 ms. Prepulse effects differed according to prepulse modality, but the OOcABR and the OOcASR were always modulated in the same way. In both responses, somatosensory prepulses induced facilitation from 20 to 50 ms, followed by inhibition beyond 75 ms, and auditory prepulses induced no facilitation but a significant inhibition beyond 30 ms. In the OOcEBR, both somatosensory and acoustic prepulses induced facilitation of R1 and inhibition of R2 beyond 30 ms. Our results suggest that the OOcABR and the OOcASR exhibit the same physiological behavior regarding prepulse modulation. It is hypothesized that prepulse facilitation is due to direct impingement of subthreshold excitatory inputs onto the facial motoneurons while prepulse inhibition results from the engagement of a presynaptic inhibitory circuit in the brainstem. Received: 9 October 1998 / Accepted: 29 April 1999