【作者】 刘忠国；

【导师】 王明时；

【作者基本信息】 天津大学 ， 生物医学工程， 2004， 博士

【摘要】 对大脑功能原理的探讨已成为当今科学研究的热门课题。本课题就大脑对连续刺激信号的诱发电位响应特性进行了研究。本课题采用成对刺激模式(paired-stimuli paradigm),研究了在如下三种刺激情况下前刺激S1对后刺激S2的诱发电位的影响问题即前脉冲抑制问题:(1)前刺激S1和后刺激S2皆为听觉刺激信号; (2)前刺激S1和后刺激S2皆为视觉刺激信号; (3)前后刺激为交叉感觉通道的刺激信号,这其中包括前刺激S1为视觉刺激而后刺激S2为听觉刺激的视觉-听觉交叉刺激,以及前刺激S1为听觉刺激而后刺激S2为视觉刺激的听觉-视觉交叉刺激。对大脑的前脉冲抑制或感觉门控机制进行研究,探讨大脑在响应感觉刺激信号时的电生理特性,确定大脑的哪些区域参与调控了大脑的感觉门控,可以推知大脑在信息处理时的工作原理,从而揭示大脑的认知功能,因此本课题有重要的理论研究意义。本文通过对前后刺激诱发电位的波形、幅值和潜伏期进行比较分析,通过绘制后刺激S2诱发电位的幅值响应曲线、峰峰值响应曲线和诱发电位能量响应曲线,展示了随着ISI的变化前刺激S1对后刺激S2诱发电位影响的规律。研究结果表明,虽然中长潜伏期诱发电位容易受到意识注意的影响,但在三种刺激情况下,前刺激S1对后刺激S2的中长潜伏期诱发电位的影响作用具有非常明显而又稳定的规律性。前刺激S1对后刺激S2的诱发电位有抑制作用,抑制作用的程度则随着刺激间时间间隔(Inter-Stimulus Interval, ISI)缩短而逐渐增强,当刺激间时间间隔(ISI)比较小时,前刺激S1完全抑制了后刺激S2的诱发电位的产生。这种抑制作用反映了大脑对有固定时间间隔的连续刺激的一种响应模式,我们提出其生理实质是脑诱发电位随ISI的缩短而产生的不应期效应,这提示了大脑连续接受外界刺激的反应能力是有一定阈值的。造成这种不应期效应和抑制作用的原因,是由大脑在信息处理中的保护机制原理造成的。前脉冲抑制的规律也揭示了大脑在信息处理时所遵循的时间优先和时间加权编码的大脑信息处理原理。视觉和听觉交叉通道刺激的实验结果从电生理的角度对McGurk效应和听觉诱导视觉幻觉现象提供了一定解释。更多还原

【Abstract】 Over the last years more and more research was focused on the exploration of the brain and its function. This research is about the brain evoked potentials (EP) response to sequential stimuli. With paired-stimuli paradigm, the influence of a preceding stimulus on the brain evoked potentials(EP) to the succeeding stimulus was studied in this research, under three kinds of stimuli as follows: (1) the preceding stimulus and the succeeding stimulus were both auditory stimuli; (2) the preceding stimulus and the succeeding stimulus were both visual stimuli; (3) the preceding stimulus and the succeeding stimulus were cross-sensory stimuli, in which two situation were included; the first situation was auditory-visual cross-modal stimuli in which the preceding stimulus was auditory stimulus and the succeeding stimulus was visual stimulus, the second situation was visual-auditory cross-modal stimuli in which the preceding stimulus was visual stimulus and the succeeding stimulus was auditory stimulus. It is important in theory to study the mechanism of prepulse inhibition or sensory gating. We can have a good understanding of the brain functions in its information processing, by exploring the brain electrophysiological characteristics in response to sequential stimuli, and by identifying the locations of the structures which contribute to the sensory gating process. The characteristics of influence of preceding stimulus S1 on the brain evoked potentials (EP) to the succeeding stimulus S2 are demonstrated, through analysis of EP waveforms, EP amplitude and EP latency, through plotting the amplitude response curves, through plotting peak-peak response curves and through plotting energy response curves. The experiment data demonstrated that the preceding stimulus S1 had a significant and robust influence on the mid-latency evoked potentials (EP) of the succeeding stimulus S2, although mid-latency evoked potentials (EP) are influenced by attention. It was found that EP of the succeeding stimulus S2 was inhibited by the preceding stimulus S1, and the inhibition level was dependent on inter-stimulus interval (ISI) of the two stimuli, the shorter the ISI the stronger the inhibition level would be. Evoked potential of the succeeding stimulus S2 was inhibited completely by the preceding stimulus S1, as the inter-stimulus interval (ISI) was shorter than a threshold value. The inhibition effect reflected the characteristics of the brain EP response to continuous stimuli with certain time interval. The theory of physiological refractory effect was put forward to explain about the inhibition effect, i.e., there is a refractory effect on brain EP response to continuous stimuli as ISI being shortened to a threshold. It demonstrated that there is a certain threshold in brain EP response when brain continuously receiving the outer stimuli. The inhibitory influence of the preceding stimulus might be caused by the neural refractory effect. Prepulse inhibition phenomena suggest that the principle of time priority encoding and time weighting encoding is followed in brain information processing. The data of visual and auditory cross-modal stimulating experiments made contribute to the electrophysiological explanation of McGurk effect and the visual illusion caused by auditory stimuli.更多还原