儿童事件相关电位N270—头皮电位分布特点及与成人的比较

目的：比较儿童与成人脑内冲突事件相关电位N270及头皮电位分布的特点，探讨冲突监测系统的发育过程。方法：20名健康学龄儿童和30名健康成人自愿者为受试者，儿童和成人分别分成两个组，其中一组人判断连续出现的对数字的颜色是否相同，不考虑数值（注意颜色组）。另一组人判断连续出现的一对数字的数值是否相同，不考虑颜色（注意数值组），同时在头皮记录事件相关电位。结果：成人在刺激在发生冲突时，（颜色不同和／或数值不同），无论在注意和不注意的状态下均可在第二个刺激出现后270ms左右引出事件相关电位N270，且分布在全头部；儿童只有被注意的刺激对的特征发生冲突时才能引出N270，注意颜色任务颜色冲突时，引出的N270分布在全头部，最高的波幅在中央和额部，注意数值任务数值冲突时，引出的N270主要分布左头中央和额部，结论：学龄儿童确实存在着冲突事件相关电位N270，其产生受注意的控制，其头皮电位的分布特点受所注意的刺激特征的影响，而成人N270的产生与注意无关，其头皮电位的分布与刺激特征无关。     

不同注意条件下人脑对视觉双特征冲突信息处理机制的脑诱发电位研究

目的:采用事件相关电位的方法,研究包含颜色和位置两种物理特征的视觉冲突信息进入大脑后,人脑冲突处理系统的工作机制以及注意系统对该系统的影响。方法:15名健康志愿者参与试验。视觉刺激为同时具有颜色和位置两种特征的圆点图片。先后呈现的两张图片(S1和S2)组成一个刺激对。3种颜色(红、黄、兰)和3种位置(屏幕中央点、水平轴上左右各距中央点100mm的两点)随机组成4种类型的刺激对,即,①S1和S2的颜色、位置均相同;②S1和S2的颜色相同,位置不同;③S1和S2的颜色不同,位置相同;④S1和S2的颜色、位置均不同。实验分为两部分,①受试者只需注意颜色特征,即判断S1和S2的颜色是否相同,并做出相应的按键反应,不管位置如何。②受试者只需注意位置特征,即判断S1和S2的位置是否相同,并做出相应的按键反应,不管颜色如何。将刺激对类型与两个任务结合起来,归纳为4种状态:匹配状态、注意无关冲突状态、注意相关冲突状态和双冲突状态。结果:注意单一特征时注意无关冲突状态、注意相关冲突状态和双冲突状态均可引出N270,注意相关冲突状态的N270波幅最高,双冲突状态引出的N270波幅高于注意无关冲突状态,且注意相关冲突状态的N270波幅等于双冲突状态和注意无关冲突状态的N270波幅之和。结论:注意单一特征时双冲突状态的N270波幅减低可能反映了注意对冲突处理系统自上而下的抑制性调节。     

工作记忆对冲突性负波N270的影响

目的:研究工作记忆对冲突性负波N270的影响.方法:实验中有数字-符号联想作业和数字-数字比较作业两种任务.实验中存在下面四种情况:①数字-符号对应;②数字-符号非对应;③数字-数字匹配;④数字-数字不匹配.呈现的第一个刺激(S1)为数字,随后呈现的第二个刺激(S2)为数字或符号,要求受试者判断S2是否与S1对应或匹配.结果:在冲突状态下,均可诱发出冲突性负波N270,且在数字-数字不匹配状态下比在数字-符号非对应状态下诱发出的N270波幅更负.结论:工作记忆负荷量的增大会影响冲突监测处理过程,从而相应地反映在N270波幅的变化上.     

刺激间隔对事件相关电位N270的影响

目的：观察刺激间隔对颜色冲突诱发的事件相关电位Ｎ２７０的影响。方法：采用美国Ｎｅｕｒｏｓｃａｎ脑电诱发电位工作站,对１５名健康受试做刺激匹配的事件相关电位研究,要求受试判断前后两个刺激的颜色是否相同,并作出按键反应,每对刺激以不同的刺激间隔呈现（ｏｍｓ,１５０ｍｓ,５００ｍｓ,１０００ｍｓ）,结果;５００ｍｓ和１０００ｍｓ状态,当一对刺激颜色不同时,在第二个刺激出现后约２７０ｍｓ处从头皮可记录     

冲突性负波N270对抑郁症患者认知功能损害的评价

目的：揭示抑郁症患者的认知功能损害,探讨在该病患者中冲突性负波N270的变化及意义。方法：顺序出现的颜色相同或不同的刺激对随机呈现。25名抑郁症患者和25名年龄、性别匹配的正常对照并判断每对刺激的颜色是否相同并相应按键反应,同时在头皮记录事件相关电位。结果：在患者组和对照组,颜色不同的刺激对均可诱发出N270。患者组N270的潜伏期延长(P_3、P_4,P＜0．05),且缺失率高于对照组(F_3,5/25；F_4,4/25),各部位N270的峰波幅显著低于对照组。结论：抑郁症患者存在认知功能损害,N270可作为评价该病认知功能障碍的一个指标。     

空间旋转角度信息冲突诱发的事件相关电位

目的:探讨人脑处理空间旋转角度信息冲突的工作机制。方法:采用美国Neuroscan脑电诱发电位工作站,对19例健康受试者做刺激匹配的事件相关电位研究,要求受试者判断前后呈现的图片中环状轮(环轮)所摆放的空间旋转角度是否相同,并作出按键反应。结果:当一对刺激所摆放的空间旋转角度不同时,可记录到一个明显的负波-N270(F1,18=26.86,P=0.000),右侧较左侧平均波幅明显偏负(F1.18=10.74,P=0.004),波幅以前头部较明显(F2,36=8.91,P=0.001)。结论:空间旋转角度的信息冲突可以诱发N270的产生。     

注意缺陷多动障碍患儿的事件相关电位改变

目的：研究注意缺陷多动障碍（attention deficit hyperactivity disorders, ADHD）患儿与正常儿童相比,事件相关电位（ERP）的变化。方法：21例确诊为ADHD的患儿及19名年龄、性别相匹配的健康志愿者进行ERP测试。以颜色不同而大小相同的圆形图片为刺激材料,两张图片颜色相同为匹配状态,不同为冲突状态。两种状态出现的机率相同。按照国际10-20系统粘贴头皮电极,在刺激序列呈现过程中按要求按键并同步记录脑电活动。结果：冲突状态的刺激时诱发出N270。与对照组相比,ADHD组患儿N270的潜伏期显著延长,差异有统计学意义。而ADHD组患儿的N190、P300的潜伏期及平均电压与对照组相比差异无统计学意义。结论：ADHD患儿ERP相对于健康儿童发生改变,其中N270更敏感。     

记忆对冲突性负波N270及反应时和正确率的影响

目的:研究记忆对冲突性负波N270及反应时和正确率的影响.方法:实验中有数字-符号联想作业和数字-数字比较作业两种任务.实验中存在下面四种情况:①数字-符号对应;②数字-符号非对应;③数字-数字匹配;④数字-数字不匹配.呈现的第一个刺激(S1)为数字,随后呈现的第二个刺激(S2)为数字或符号,要求受试者判断S2是否与S1对应或匹配.结果:在冲突状态下,均可诱发出冲突性负波N270,且在数字-数字不匹配状态下比在数字-符号非对应状态下诱发出的N270波幅更负.同时还发现数字-符号联想作业的反应时间比数字-数字比较作业的反应时间明显延长以及数字-数字比较作业的正确率比数字-符号联想作业的正确率明显提高的现象.结论:工作记忆负荷量的增大会影响冲突监测处理过程,从而相应地反映在N270波幅的变化上,同时也会引起正确率和反应时等行为学指标相应的改变.     

人脑对视觉信息变化的处理过程的事件相关电位研究

目的:采用256导联事件相关电位技术和低分辨率电磁图的方法,研究人脑对视觉信息变化的处理过程.方法:12名健康志愿者参与试验.视觉刺激为同时具有颜色和形状2种特征的图形.先后呈现的2张图片(S1和S2)组成一个刺激对并分为4种类型:S1和S2的颜色、形状均相同;S1和S2的颜色相同,形状不同;S1和S2的颜色不同,形状相同;S1和S2的颜色、形状均不同.受试者分别完成注意颜色和注意形状2个任务.结果:①S2呈现后135 ms～165 ms,3种变化的刺激对引出了变化相关正波(change-related positivity,CRP).低分辨率电磁图(low-resolution electromagnetic tomography,LORETA)分析显示CRP的发生源是枕叶舌回、楔叶.②235 ms～275 ms时间窗内,无变化和无关变化状态引出了N200,右侧颞叶梭状回、颞中回和海马旁回是该成分的发生源.③240 ms～320 ms时间窗内,所有变化的刺激对均引出了N270,前扣带回和双侧杏仁核是N270的发生源.结论:人脑对视觉信息变化的处理过程可分为3个阶段:CRP所代表的可能是人脑对视觉信息变化的早期处理阶段;N200所反映的可能是人脑对无关信息变化的主动忽略阶段;N270可能代表高级处理阶段.     

厌恶启动后黑白颜色中性词加工的时间特征:来自ERPs的证据

目的:采用事件相关电位技术(ERPs)和语义启动范式,探讨道德厌恶启动后对黑白颜色中性词加工的时间特征及其神经机制。方法:采用双字词启动范式,先呈现启动词(道德厌恶词、非道德厌恶词),然后再呈现目标词(黑颜色中性词、白颜色中性词),要求被试对目标词的字形结构作判断。通过探讨不同组合在脑电指标上的差异来探讨其加工特征。结果:与非道德厌恶刺激相比,道德厌恶启动后黑颜色中性词诱发了更大的N1和N350波幅。结论:与非道德厌恶相比,道德厌恶启动后与道德概念的隐喻相关黑白颜色的目标词获得了更多的认知资源,受到了更精细的加工。道德厌恶启动后个体通过更倾向于隐喻道德纯洁的白色,以缓解和释放厌恶感,保持良好的自我道德意象。     

Event-related potentials evoked by multi-feature conflict under different attentive conditions

Event-related potentials (ERPs) were recorded in subjects while they were performing a matching task. The focus of the present study was on the contributions made by ERP recording to revealing the time-course of multi-conflict information processing in the brain during visual attention. Participants were instructed to discriminate whether the attributes of the first stimulus (S1) were the same as those of the second one (S2) of a pair. Stimuli were defined by three features: color, global shape, and local shape. In condition 1, all attributes of the two stimuli of the pair were constant (no conflict); in condition2, S2 was different from S1 in all attributes (conflict). The experiment comprised three tasks. In task 1, subjects attended to the color of the stimuli and ignored the other attributes. In task 2, they were asked to attend to both color and global shape of stimuli and disregard the local shape. In task 3, all attributes were attended to. An ERP component N270 was elicited by attending to the color conflict in session one. In task 2, attending to color and global shape induced two ERP effects in the conflict condition: N270 and N400. The results suggest that the attended different conflicts of the two visual attributes of the stimuli were processed in series. However, in task 3, only one apparent negative component, N270, was observed in the conflict condition. The difference between data from task 2 and 3 showed that more than one processing model exists in the human brain for processing multiple visual attribute conflicts. Electronic Publication     

The active inhibition for the processing of visual irrelevant conflict information.

We applied event-related potentials (ERPs) to assess brain activities with inhibition of irrelevant conflict information processing during visual selective attention. Fifteen healthy subjects matched two sequentially presented color spots (S1 and S2) in a visual selective attention task. The two spots might be presented in a fixed position of either the same color (match), or different colors (color conflict). They might be in different positions of the same color (position conflict), or different colors (color and position conjunction conflicts). Subjects matched the stimuli in two different sessions according to different attention tasks: attending to color (Ac) or attending to position (Ap). In the time window of 201-350 ms after the onset of S2, an ERP component the N270, was elicited in all the conflict conditions with the amplitude enhanced in the task-relevant conflict. The amplitude of the N270 in the conjunction conflict condition was lower than that of the task-relevant conflict condition in either Ac or Ap session. The results suggest that the conflict processing is modulated by attention. All kinds of conflicts might be processed in a common system in the human brain, the conflict processing system. Due to the limited capacity of the conflict processing system, the decrement of the N270 in the conjunction conflict condition is deduced to reflect an active inhibition for the processing of the irrelevant conflict.     

Event-Related Potentials During Memory Search and Selective Attention to Letter Size and Conjunctions of Letter Size and Color

The analysis of event-related potentials was used in two experiments to investigate the structure of information processing in a task in which subjects selectively attended to letter size (Experiment 1) or a conjunction of letter size and color (Experiment 2) and searched for target letters within the attended stimulus category. The event-related potentials showed that selective attention to letter size resulted in the enhancement of a central N2b component (onset about 200 ms), which was assumed to reflect feature nonspecific orienting of attention. When attention was directed to conjunctions of letter size and color an earlier effect was found (onset about 150 ms) consisting of positivity at the anterior electrodes and negativity at OZ. This earlier effect was assumed to reflect feature-specific selective processing. Although the early effect showed a hierarchical pattern of results, in which the effect of attending to size was contingent on the relevance of the color attribute, the N2b showed a more independent pattern of results, in which the relevance of either the color or the size attribute resulted in an enhancement of this component, independent of the relevance of the other attribute. An increase in the duration of the memory search process resulted in a prolonged negativity with an onset of about 200 ms which was maximal at CZ. In both experiments the initial phase of this negativity was also found in the event-related potentials to the unattended stimulus categories, suggesting that the search process was initiated nonselectively and terminated after the selection cues were identified. Detection of attended target letters resulted in a parietal P3b component. In both experiments there was an earlier effect discriminating targets and nontargets in the range 200-300 ms.     

The sequential processing of visual feature conjunction mismatches in the human brain

To clarify the brain mechanism for multifeature stimulus comparison, subjects matched the features of two serial visual stimuli in pairs. Stimulus pairs were of four categories: C-S-, color same, shape same (match); C-S+, color same, shape different (shape mismatch); C+S-, color different, shape same (color mismatch); C+S+, color different, shape different (conjunction mismatches). Subjects matched the stimuli in three different sessions according to different attention tasks: attending to color (Ac), attending to shape (As), or attending to both color and shape (Acs). A negative one-peak brain potential, N270, was elicited in all the mismatch conditions with amplitude enhanced in the task-relevant mismatch. Negative potential with two peaks, N270 and N400, appeared when attending to the conjunction mismatches concurrently. The two serial negativities in response to attended feature conjunctions might reflect the temporal different stages for processing conjunction mismatches or conflicts.     

Various conflicts from ventral and dorsal streams are sequentially processed in a common system

Event-related potentials (ERPs) were recorded in subjects while they were matching two sequentially presented color spots. The two spots might be presented in the same position of the same color, or different colors (color conflict). They might be in different positions of the same color (position conflict), or different colors (color and position conjunction conflicts). Subjects matched the stimuli in three different sessions according to different attention tasks: attending to color, attending to position, or attending to both color and position. A negative one-peak brain potential, N270, was elicited in all the conflict conditions with amplitude enhanced in the task-relevant conflict. Two negative effects, N270 and N400, were recorded when attending to the conjunction conflicts concurrently. Visual spatial information is processed through the dorsal stream, while the feature information is processed through the ventral stream in the brain. The results suggest that all kinds of conflicts might be processed in a common system above the level of the two streams, which processes the conjunction conflict information from ventral and dorsal stream in series.     

The Effects of Spatial Selective Attention on the Somatosensory Event-Related Potential

Event-related potentials (ERPs) were recorded during a selective attention task involving weak or strong electrical stimuli delivered to the index fingers of the left and right hands. In an attend weak condition, subjects were asked to count the number of weak stimuli (targets) interspersed amongst strong stimuli (standards) delivered to a designated hand, whilst ignoring a similar set of stimuli delivered to the other hand. In an attend strong condition, subjects were asked to count the number of strong targets interspersed amongst weak stimuli. In both conditions, targets and standards occurred with probabilities of .10 and .40 respectively on each hand. Counting weak targets was found to be more difficult than counting strong targets. The latency of the earliest significant effect of selective attention on ERPs to standards was dependent on stimulus intensity: N80 in the case of weak standards, P105 for strong standards. There was no evidence of a later prolonged negative shift in attended standard ERPs. Rather, an enhanced N150 component post-centrally was followed by a prolonged positive shift of attended standard ERPs. This Late positive shift had a similar scalp distribution to the late positive component elicited by attended target stimuli.