瞬态诱发耳声发射信号的定量分析

为探索在瞬态诱发耳声发射 (TEOAE)检测中 ,耳声发射信号的强度、信噪比、频段相关率等定量指标的有效算法 ,论文采用频域相干谱法对 TEOAE信号进行频段相关率分析 ,克服了传统带通滤波器法受滤波器性能影响的弊病 ,有效地解决了从频域衡量时域波形相似性的问题。同时采用基于信号差互谱分析的方法来计算 TEOAE信号的强度、总信噪比及频段信噪比。近 2 0 0例临床 TEOAE实测结果表明 ,由这些算法得到的定量指标是临床诊断的有效依据 ,因而这些算法是 TEOAE定量分析的有效方法。     

用瞬态诱发耳声发射信号识别听神经病

听神经病是一种特殊的感音神经性耳聋,目前对其病变部位和发病机理的认识仍有争议,诊断方法也较为复杂。该文探讨利用瞬态诱发耳声发射(TEOAE)信号识别听神经病的可行性。采用前馈神经网络,以TEOAE信号的自回归模型功率谱为特征,对正常耳和听神经病耳的TEOAE信号进行分类识别,总正确率可达88.67%,说明了利用TEOAE信号对听神经病进行识别的可行性。该方法对听神经病的识别具有一定意义,若应用于新生儿听力筛查中,将有助于降低新生儿听神经病的漏检率。     

稳态体感诱发电位的提取与分析

对人体施加较高频率的电流刺激可以引起稳态体感诱发电位。为了诱发并提取出稳态体感诱发电位,该文设计并实现了一种可由计算机精确控制刺激电流的强度和频率等参数的新型体感诱发电位刺激器,给出了提取稳态体感诱发电位的检测方法,还讨论了能够在实验过程中减少刺激伪迹的措施。同时,给出了一种可在较短时间及噪声环境下提取出稳态体感诱发电位的频域分析方法,并与提取瞬态诱发电位采用的叠加平均方法进行了比较。理论分析与实验结果表明,该方法可以在较短时间内用头皮电极提取出稳态体感诱发电位,可以用在术中监护受试者的神经传导水平,而且其幅值的分布能够反映大脑对体感刺激的响应。     

视觉诱发电位在人体视觉舒适性研究中的应用

建筑室内色温水平会影响人员的工作效率、视觉舒适性等。收集了不同色温水平下15名受试者的图像翻转视觉诱发电位(pattern reversal visual evoked potential, PRVEP)数据和主观调查投票数据,采用模糊熵分析方法对客观生理参数进行分析,并基于PRVEP模糊熵与主观调查之间存在的极强相关性和生理上反应的相似性建立二者的数理关系,以使用客观生理指标预测主观感受,更加准确地实现对人体主观视觉舒适度的预测。研究发现在不同色温下人体PRVEP模糊熵和刺激程度投票值都随着色温的增大而逐渐增大,而眼部疲顿度则呈现出先减小后增加的变化趋势。高色温的冷色调环境下人体PRVEP模糊熵和主观调查值最大,应对刺激时的生理反应最强烈,舒适性不佳。而在4 000 K左右的中性色温环境下PRVEP模糊熵和刺激程度会略微增加但眼部疲顿度会减小,更适宜的色温工作环境有助于提高舒适感和工作效率。     

基于Golay序列调制的视觉诱发电位脑机接口系统

脑机-接口是一种新型的人机交互方式,不依赖于外周神经和肌肉,而是直接将脑电信号翻译成计算机的控制命令。针对传统脑机-接口系统识别准确率低、可识别目标少等问题,提出了一种基于Golay序列调制的视觉诱发电位脑机接口系统。首先受试者必须注视着屏幕上闪烁的目标,通过脑电放大器对人脑表皮层产生的信号进行采集、放大、A/D转换等预处理操作,然后经过实时分析软件对预处理后的脑电信号进行分类识别,取出大脑特定获得下的特征;最后将其转换为计算机的控制命令,并将输出结果反馈给用户。系统选取了Golay序列对刺激目标进行调制,且运用模板匹配法对目标进行识别。实验结果表明,该方法能有效的识别刺激目标,且获得了93.75%的识别准确率。     

Sustained firing in auditory cortex evoked by preferred stimuli

It has been well documented that neurons in the auditory cortex of anaesthetized animals generally display transient responses to acoustic stimulation, and typically respond to a brief stimulus with one or fewer action potentials. The number of action potentials evoked by each stimulus usually does not increase with increasing stimulus duration. Such observations have long puzzled researchers across disciplines and raised serious questions regarding the role of the auditory cortex in encoding ongoing acoustic signals. Contrary to these long-held views, here we show that single neurons in both primary (area A1) and lateral belt areas of the auditory cortex of awake marmoset monkeys (Callithrix jacchus) are capable of firing in a sustained manner over a prolonged period of time, especially when they are driven by their preferred stimuli. In contrast, responses become more transient or phasic when auditory cortex neurons respond to non-preferred stimuli. These findings suggest that when the auditory cortex is stimulated by a sound, a particular population of neurons fire maximally throughout the duration of the sound. Responses of other, less optimally driven neurons fade away quickly after stimulus onset. This results in a selective representation of the sound across both neuronal population and time.     

Activation of protein kinase C augments evoked transmitter release

In view of the emerging role of the phosphoinositide system in cellular communication we examined its involvement in quantal-transmitter release, which is a key element in synaptic transmission. Transmitter release is normally activated by an increase in intracellular calcium, achieved either by entry of calcium ions through the presynaptic membrane or by intracellular calcium liberation. One of the targets of the phosphoinositide signalling system is the enzyme protein kinase C (PKC), which can be activated experimentally by tumour promoting phorbol esters, including 12-O-tetradecanoylphorbol-13-acetate (TPA). Such activation of PKC may be implicated in transmitter release in two ways. First, phorbol esters were found to increase secretion and enhance calcium currents; it might therefore be expected that they would increase synaptic transmitter release. But phorbol esters also inhibit the calcium current in dorsal root ganglion neurones. We report that the phorbol ester TPA augments synaptic transmission at the neuromuscular junction by increasing transmitter liberation. Activation of PKC also depends synaptic depression.     

对脑干听觉诱发电位相关维数的研究

用二维延时重构技术重构了脑干听觉诱发电位时间序列，并用Ｇｒａｓｓｂｅｒｇｅｒ－ｐｒｏｃａｃｃｉａ算法计算了正常人与有听觉障碍病人的关联积分Ｃ（ｒ）。     

Spontaneous and evoked activity of fetal primary afferents in vivo

The first movements of the fetus are apparently random and spontaneous. Their onset coincides with the growth of dorsal root afferents into the spinal cord and it is possible that they are not simply a result of spontaneous motoneuron activity but are reflex responses to sensory stimulation. It is not clear what stimuli could normally evoke such reflexes because nothing is known of the properties of primary afferent neurons in the fetus. I have investigated this by making recordings from single dorsal root ganglion cells in fetal rats in vivo. The afferents have small, defined receptive fields and respond to mechanical stimulation of skin or muscle at intensities that might occur in utero. Many of them are also chemosensitive. Unlike postnatal afferents they display background activity which peaks at the same age as fetal movements. Repeated stimulation causes long-lasting increases of both background and evoked activity. Such sensory input is likely to have a considerable influence on fetal movements and on the development of spinal cord connections.     

相位同步方法用于稳态视觉诱发电位的测量

稳态视觉诱发电位(SSVEP)被广泛用于脑-机接口和脑电的稳态标记频率检测中.在这些研究中,都需要解决一个问题:当视觉刺激的频率发生变化时,如何通过分析SSVEP信号,快速准确地跟踪上这种变化.解决这个问题通常的分析方法是利用信号的频谱特征.该文依据稳态视觉诱发电位与视觉刺激之间的时间锁定关系,提出用相位同步化方法来解决这个问题.实验结果表明,相位同步化方法能够更加准确地定位刺激频率的变化时刻.在SSVEP研究中,相位同步化可以作为一个新的可资利用的特征.