【作者】 刘明亮；

【导师】 柯余峰；

【作者基本信息】 天津大学 ， 生物医学工程， 2022， 硕士

【摘要】 视觉灰度分辨能力反映了人类视觉系统的一种视觉敏感度,在很多特定工作环境中具有重要应用价值。当前研究对于视觉灰度分辨任务中的特异性脑电活动研究尚不足,同时对于经颅电刺激影响视觉感知功能的调控作用规律仍然不明确。本论文针对以上问题,一方面探究视觉分辨任务的行为表现与脑电特征之间的联系,为深入理解视觉分辨能力的神经表征提供依据;另一方面探究不同模式经颅电刺激对视觉分辨能力及大脑功能活动的调控作业规律,为调控视觉敏感性提供依据。本论文具体工作内容如下:首先,本文设计了视觉灰度差检测的对比度敏感性测试任务范式,根据每名被试的视觉分辨能力测试结果设定了个性化的灰度差参数。并设计了四种模式的高精度视觉区经颅电刺激方案,分别为经颅直流电刺激(t DCS)、个性化alpha峰值频率经颅交流电刺激(IAF-t ACS)、40Hz经颅交流电刺激(40Hz-t ACS)和伪刺激对照实验。18名受试者均进行了四次实验,并记录行为学和脑电数据。然后,本文对比分析了不同反应试次和不同刺激类型之间的行为学和事件相关电位(ERP)特征。结果发现,灰度差检出(Hit)试次的P3成分幅值显著大于未检出(Miss)试次,而Miss试次P3潜伏期和反应时均显著大于Hit试次,并且Hit试次的潜伏期与反应时之间表现出更强的相关性。有灰度差的靶刺激(Target)试次与无灰度差的非靶刺激(Non-target)试次的P3幅值未呈现显著性差异,但Target试次的P3潜伏期和反应时均显著小于Non-target试次,并且Target试次的P3潜伏期和反应时之间表现出更强的相关性。最后,本文对四种电刺激前后的行为学变化和脑电特征变化进行分析。行为学分析发现,与伪刺激相比,IAF-t ACS刺激后检出率显著下降、反应时间显著上升,40Hz-t ACS、t DCS刺激未表现出显著性差异。ERP特征分析发现,40Hz-t ACS后P3幅值显著降低,IAF-t ACS后N2幅值有下降趋势。事件相关谱扰动分析发现,40Hz刺激后高beta频带事件相关去同步(ERD)减弱,IAF刺激后的alpha和beta频带ERD增强、gamma频带事件相关同步(ERS)减弱。本文通过视觉灰度分辨任务的动态认知过程,证明视觉灰度分辨脑电特征与行为学指标之间存在显著相关性,并初步证实了不同经颅电刺激模式对视觉分辨功能的调节作用,可为后续探究更有效的视觉功能神经调控方法提供依据。更多还原

【Abstract】 Visual gray-level discrimination is a kind of visual sensitivity of human visual system and has important application value in many special working environments.At present,there were insufficient studies on specific EEG activity in visual gray-level discrimination task,and the modulation effect of transcranial electrical stimulation on visual perception function was still unclear.To the above problems,this paper explored the relationship between behavioral performance and EEG features of visual discrimination task,provided the basis for understanding the neural representation of visual discrimination.On the other hand,the modulation rules of different modes transcranial electrical stimulation on visual discrimination performance and brain functional activities were investigated to provide a basis for the modulation of visual sensitivity.The specific work content of this paper was as follows:Firstly,this paper designed the visual gray-level difference detection paradigm for measuring contrast sensitivity,and set personalized gray-level difference parameters according to the visual discrimination test results of each subject.Four modes of high definition transcranial electrical stimulation on visual cortex were designed,including transcranial direct current stimulation(t DCS),individual alpha peak frequency transcranial alternating current stimulation(IAF-t ACS),40 Hz frequency transcranial alternating current stimulation(40Hz-t ACS)and sham stimulation control modes.Each of 18 subjects conducted four experiments,while behavioral performance and EEG data were recorded.Then,the behavioral and event-related potential(ERP)features of different response trials and different stimuli types were compared and analyzed.The results showed that the amplitude of P3 component in Hit trials was significantly larger than that in Miss trials,and the latency and response time of Miss trials were significantly larger than those of Hit trials,and there was a stronger correlation between the latency and response time of Hit trials.There was no significant difference in P3 amplitude between Target trials with gray difference and Non-target trials without gray difference,but P3 latency and response time of Target trials were significantly smaller than Nontarget trials.Moreover,P3 latency and response time of Target trials showed a stronger correlation.Finally,the changes of behavior and EEG features before and after four modes of electrical stimulation were analyzed.Behavioral analysis results showed that,compared with sham stimulation,the detection rate reduced significantly and the response time increased significantly after IAF-t ACS,while 40Hz-t ACS and t DCS showed no significant difference.ERP features analysis results showed that P3 amplitude decreased significantly after 40Hz-t ACS and N2 amplitude showed a decreased trend after IAF-t ACS.The event-related spectral perturbation analysis results showed that the event-related de-synchronization(ERD)phenomenon in high-beta band weakened after40Hz-t ACS,the ERD phenomenon in alpha and beta band enhanced significantly but the event-related synchronization(ERS)phenomenon in gamma band weakened significantly after IAF-t ACS.Through dynamic cognitive process of visual discrimination task,this study proved that there was a significant correlation between EEG features and behavioral performance of visual gray-level discrimination,and preliminarily confirmed that different transcranial electrical stimulation modes had specific modulation effect on visual discrimination function,which provided the basis for further exploring effective neural modulation method of visual function.更多还原