时间知觉和关联负变化

关联负变化（contingent negative variation, CNV）被认为是与时间知觉过程有关的ERP成份。有关研究发现,CNV波幅会随着时间知觉到的长度和时间知觉的准确性而发生变化;CNV波幅的潜伏期与时间比较的判断决策过程有关;时间知觉中所诱发的CNV的脑内源存在历时性激活的特点且存在半球效应。为了进一步揭示时间知觉的神经机制,还需要结合具有高空间分辨率的脑成像技术和神经心理学的研究     

不同时距加工机制的比较:来自ERP的证据(Ⅰ)

采用事件相关电位的方法分析了不同时距加工机制的差异。实验采用时间两分任务,要求被试形成短(400ms)和长(1600ms)的时间判断标准,然后对7个刺激系列进行短、长的判断。结果表明时间知觉过程可以诱发出一种类似于CNV的慢性负波。对于400ms的短时距加工存在显著的半球效应,右半球的波幅显著高于左半球。1600ms的时距加工没有表现出明显的半球效应。不同时距的加工存在显著的差异。1600ms比400ms加工诱发出更大的CNV波幅。     

视觉工作记忆内容对自上而下注意控制的影响：一项ERP研究

采用视觉搜索范式, 以二维抽象对称图形为材料, 通过记录\16名被试在长短两种时间间隔(ISI)条件和有效、中性、无效三种视觉工作记忆内容条件下的行为反应和事件相关电位(ERPs), 探讨视觉工作记忆内容对自上而下注意控制影响的认知过程和脑机制。结果发现：(1)无论ISI长或短, 有效信息条件(记忆图形与目标所在的背景图形相同)的反应时均显著短于无效信息条件(记忆图形与目标所在的背景图形不同)。(2)有效信息条件下的额区P2波幅显著大于中性信息条件(记忆图形不出现在搜索序列中); 枕区P1、N1波幅和潜伏期在视觉工作记忆内容条件下差异不显著; 短ISI条件下, 有效信息条件下的枕区P300波幅显著大于无效信息条件; 长ISI条件下, 有效信息条件的枕区P300波幅显著小于无效信息条件。表明当目标出现在与记忆内容相匹配的客体中时, 激活了工作记忆中的客体表征, 以自上而下的方式优先捕获注意; 同时ISI变化对此过程起着调节作用。     

认知判断中手部动作模拟的fMRI研究

该研究采用功能磁共振成像技术,考察不同条件下进行工具认知判断时手部姿势对认知判断的影响及动作模拟的神经机制。实验发现：手部姿势存在显著的主效应,冲突手部姿势条件下反应时最慢,且冲突手部姿势条件下与不冲突手部姿势条件下、自然状态条件下反应时存在显著差异,自然状态条件与不冲突手部姿势条件下反应时不存在显著差异。另外,f MRI成像结果发现,额中回、额下回、顶下小叶以及辅助运动区在自然状态下有显著激活,表明个体在进行认知判断过程中有动作模拟过程;海马结构、扣带回及楔前叶等与记忆有关的脑区有显著激活,表明身体经验在认知过程的作用。总的研究表明,不同的手部姿势状态对认知判断有不同影响,冲突手部姿势会对动作模拟产生干扰作用,手部动作模拟的神经机制主要涉及镜像神经元区,且在认知判断时存在具身效应。     

期望中断效应的注意共享解释-来自ERP的证据

以1700毫秒和2300毫秒为考察时距,采用时距复制任务,对编码阶段的中断位置进行操纵,并记录了14名大学生在进行时距复制任务时编码阶段的事件相关电位(ERP).行为结果发现:分别就1700毫秒和2300毫秒而言,中断位置越靠后,复制时距越短.脑电结果发现:无中断条件的(控制任务1)编码阶段在350～550毫秒和350～1150毫秒的CNV平均波幅分别较中断位置为550毫秒的条件和中断位置为1150毫秒条件显著更高;无中断条件的(控制任务2)编码阶段在350～750毫秒和350～1550毫秒的CNV平均波幅分别较中断位置为750毫秒的条件和中断位置为1550毫秒条件显著更高.这说明了间断编码的时间复制任务中存在期望中断效应且以注意共享机制解释期望中断效应得到了电生理学证据的直接支持.     

1秒以上时距判断的ERP研究

以视觉呈现时距信号,采用时间泛化范式要求被试判断5种探测时距(1～4秒)与标准时距(2秒)之间的长度关系,并记录11名大学生在时距判断过程中的事件相关电位(ERP),继而探讨不同探测时距条件下CNV波幅特征变化以及左、右侧额叶在时距判断中的功能。结果发现:1秒、1.42秒以及2秒条件下,CNV波幅峰出现在探测时距结束点,2.84秒、4秒条件下,CNV波幅峰出现在大约2秒处(标准时距);CNV负性翻转至基线位置在1秒、1.42秒、2秒条件下随探测时距的增长而延后,而在2.84秒、4秒两种条件下无显著差异;左、右侧额叶处诱发的CNV波幅峰潜时在2.84秒、4秒探测时距条件下无显著差异,且均在2秒附近。这说明在1秒以上视时距判断中CNV波幅峰反映了基于记忆中标准时距的时距判断的决策过程;CNV负性翻转至基线位置与时距判断的决策阶段存在共变关系,CNV负性翻转至基线位置相当于负荷解脱过程中的一个由负翻正的转折点;左、右侧额叶均参与了时距脉冲累加过程。     

嗓声鉴别的脑事件相关电位研究

该项工作研究了21名女大学生和研究生鉴别两个陌生人的噪声时,六个脑区的事件相关电位(ERPs)。结果表明,双音节语义嗓声的鉴别更易引起明显的ERPs变化;两个陌生人嗓声不等概率呈现,较等概率呈现更易引起明显的ERPs变化。在单音节嗓声鉴别中,在左额区引起N200波波幅增高;而在右颞区引起P300波潜伏期的增长。在双音节语义嗓声鉴别中,除右顶叶外在其它五个脑区引起P300波波幅增高,在右额区引起P300波潜伏期明显缩短。     

听觉失匹配负波反映自动加工──感觉道间选择性注意时的新证据

为考察听觉失匹配负波是否反映自动加工,实验改进了视觉和听觉刺激同时呈现的感觉道间选择性注意实验模式,更好地控制了非注意听觉条件。结果发现,在注意与非注意听觉条件下,听觉偏离刺激均诱发出失匹配负波;注意听觉刺激时１４０－１８０ｍｓ的偏离相关负波与非注意时该时程负波的平均波幅之间无显著差异,而注意时１８０－２２０ｍｓ的偏离相关负波的平均波幅大于非注意时同一时程之负波;非注意听觉时失匹配负波的平均波幅和峰潜伏期不受视觉道任务难度的影响,该结果为听觉失匹配负波反映自动加工的观点提供了进一步证据。     

外语焦虑、紧张情绪与认知负荷对外语说谎的影响：来自中-英双语者的证据

采用错误陈述范式探究中-英双语者用母语和外语说真话和说谎时的认知神经差异, 涉及外语焦虑、认知负荷和说谎诱发的紧张情绪。对P200和CNV观察发现：(1)中-英双语者用英语说真话的P200波幅比用母语大, 说明被试用英语说话时受外语焦虑情绪影响; (2)中-英双语者用英语说谎与说真话的P200波幅无显著差异, 但用母语说谎和讲真话的P200波幅差异显著, 说明被试用外语说谎没有用母语说谎诱发的紧张情绪大; (3)中-英双语者说谎时的CNV波幅比说真话时大, 说明被试说谎比说真话的认知负荷更大; (4)中-英双语者用英语说谎时的CNV波幅比用汉语说谎时大, 说明被试用外语说谎比用母语说谎产生了更大的认知负荷。相关分析表明, 英语熟练程度是影响中-英双语者用母语和外语说谎时的认知神经差异的重要变量。     

环性传递结构的启动优势及脑电证据

采用三词对材料构成两种结构的社会情境：环性传递结构和线性传递结构,通过合理情境判断任务和脑电技术,探讨社会结构的加工机制。结果发现,与线性结构相比,环性结构引发显著的启动优势效应,诱发额区和中央区更小P200波幅、更大N400波幅和更小P600波幅。这表明,被试对环性社会结构具有自动化的整体加工优势。可能的解释指向中华文化的环性结构图式偏好,支持社会结构认知的文化建构性观点。     

The contingent negative variation laterality and dynamics in antisaccade task in normal and unmedicated schizophrenic subjects

Contingent negative variation (CNV) topography, hemispheric asymmetry and time-course were investigated in healthy subjects and non-medicated paranoid schizophrenic patients in two antisaccade paradigms with the short (800-1000 ms) and long (1200-1400 ms) durations of the fixation period. EEG and electrooculogram (EOG) were recorded. Saccade characteristics and mean amplitudes of slow cortical potentials time-locked to peripheral target were analyzed in 23 healthy volunteers and 19 schizophrenic patients. Compared to healthy control subjects, schizophrenic patients had significantly slower antisaccades and committed significantly more erroneous saccades in the both antisaccade tasks. The prolongation of the fixation period resulted in noticeable decrease of error percent in patients group. The analysis of CNV time-course has revealed two distinct stages in both groups. The early CNV stage was represented by a negative wave with the maximal amplitude over midline fronto-central area, and the late stage was characterized by increased CNV amplitude at the midline and left parietal electrode sites. In healthy subjects the simultaneous activation of frontal and parietal areas was observed in the paradigm with the shorter fixation interval; the increase of the fixation period produced consecutive activation of these areas. Schizophrenic patients' CNV amplitude was generally smaller than that of healthy subjects. The most pronounced between-group differences of the negative shift amplitude were revealed at frontal electrode sites during the early CNV stage in both modifications of the antisaccade task. The deficit of frontal activation revealed in patients at the early stage of antisaccade preparatory set in both antisaccadic paradigms may be related to pathogenesis of paranoid schizophrenia.     

Frontal and parietal EEG asymmetries interact to predict attentional bias to threat

Frontal and parietal electroencephalographic (EEG) asymmetries mark vulnerability to depression and anxiety. Drawing on cognitive theories of vulnerability, we hypothesise that cortical asymmetries predict attention to threat. Participants completed a dot-probe task in which bilateral face displays were followed by lateralised targets at either short (300 ms) or long (1050 ms) SOA. We also measured N2pc to face onset as an index of early attentional capture. At long SOA only, frontal and parietal asymmetry interacted to predict attentional bias to angry faces. Those with leftward frontal asymmetry showed no attentional bias. Among those with rightward frontal asymmetry those with low right parietal activity showed vigilance for threat, and those with high right parietal activity showed avoidance. Asymmetry was not related to the N2pc or to attentional bias at the short SOA. Findings suggest that trait asymmetries reflect function in a fronto-parietal network that controls attention to threat.     

Cognitive basis of individual differences in speech perception,production and representations: The role of domain general attentional switching

This study investigated whether individual differences in cognitive functions, attentional abilities in particular, were associated with individual differences in the quality of phonological representations, resulting in variability in speech perception and production. To do so, we took advantage of a tone merging phenomenon in Cantonese, and identified three groups of typically developed speakers who could differentiate the two rising tones (high and low rising) in both perception and production [+Per+Pro], only in perception [+Per–Pro], or in neither modalities [–Per–Pro]. Perception and production were reflected, respectively, by discrimination sensitivity d′ and acoustic measures of pitch offset and rise time differences. Components of event-related potential (ERP)—the mismatch negativity (MMN) and the ERPs to amplitude rise time—were taken to reflect the representations of the acoustic cues of tones. Components of attention and working memory in the auditory and visual modalities were assessed with published test batteries. The results show that individual differences in both perception and production are linked to how listeners encode and represent the acoustic cues (pitch contour and rise time) as reflected by ERPs. The present study has advanced our knowledge from previous work by integrating measures of perception, production, attention, and those reflecting quality of representation, to offer a comprehensive account for the underlying cognitive factors of individual differences in speech processing. Particularly, it is proposed that domain-general attentional switching affects the quality of perceptual representations of the acoustic cues, giving rise to individual differences in perception and production.     

Time perception and attention: The effects of prospective versus retrospective paradigms and task demands on perceived duration

This research was designed to compare time judgments obtained under prospective conditions (in which subjects are instructed to attend to time) and retrospective conditions (in which subjects are unaware that they will be required to judge time). In Experiment 1, subjects prospectively or retrospectively judged the duration of intervals spent performing a perceptual-motor task at different levels of difficulty. The results showed that subjects tested under both research paradigms tended to give increasingly shorter and/or more inaccurate time judgments with increases in nontemporal task demands. Experiment 2 was designed to test the effects of attentional deployment on perceived time by comparing prospective and retrospective judgments under control, selective attention, and divided attention conditions. Both types of time judgments became increasingly inaccurate as attention was more broadly deployed. The results of these experiments are consistent with an attentional allocation model, and they suggest that nontemporal task demands disrupt or interfere with timing in both prospective and retrospective situations.     

Components of attentional set-switching

A series of distinct event-related potentials (ERPs) have been recorded from the scalp of human subjects as they switch from one task to another. It is possible that task switching may depend on different mechanisms depending on whether the switch requires a change in attentional set, in other words the redirecting of attention to different aspects of a sensory stimulus, or whether it requires a change in intentional set, in others words a change in the way that responses are selected. To address this issue, the current study recorded ERPs while subjects switched between attentional sets and the results were compared with those of a previous investigation in which subjects switched between intentional sets. Subjects selected stimuli according to two conflicting attentional sets, each emphasizing one visual stimulus dimension (colour, shape). Pairs of stimuli, only one of which was to be attended, were presented for between eight and seventeen trials then either a switch or a stay cue was shown. The switch cue instructed subjects to switch from the current attentional set to the other set, while the stay cue instructed subjects to maintain the current set. Comparing ERPs time-locked to the switch and stay cues revealed neural correlates of the initiation of a task switch. Comparing the ERPs time locked to the first stimuli after either stay or switch cues identified neural correlates of the implementation of a task switch. A similar modulation over parietal electrodes was seen when subjects were switching between either attentional or intentional sets. While an intentional set switch began with a medial frontal modulation, attentional set switching began with a lateral frontal modulation. Implementing a new attentional set was associated with modulation of relatively early visual potentials, while implementing a new intentional set was associated with modulation of later response-related potentials. The results confirm that task switching consists of a number of constituent processes which may be taxed to different degrees depending on whether a task-switch paradigm requires subjects to change the way in which they select stimuli or responses.     

Anticipatory attention during the sleep onset period

To examine whether anticipatory attention or expectancy is a cognitive process that is automatic or requires conscious control, we employed a paired-stimulus event-related potential (ERP) paradigm during the transition to sleep. The slow negative ERP wave observed between two successive stimuli, the Contingent Negative Variation (CNV), reflects attention and expectancy to the second stimulus. Thirteen good sleepers were instructed to respond to the second stimulus in a pair during waking sessions. In a non-response paradigm modified for sleep, participants then fell asleep while tones played. As expected, N1 decreased and P2 increased in amplitude systematically with the loss of consciousness at sleep onset; the CNV was increasingly more positive. Sleep onset latency was correlated with the amplitude of the CNV. The systematic attenuation of the CNV waveform at sleep onset and its absence in sleep indicates that anticipatory attention requires endogenous conscious control.     

Mechanisms for attentional modulation by threatening emotions of fear,anger, and disgust

Appropriately attending to threatening environmental stimuli is evolutionarily adaptive and crucial for survival. This study revealed that nonconscious attentional modulation of disgust has different behavioral and event-related potential (ERP) patterns, as compared to fear and anger. To facilitate its evolutionary purpose of avoidance, disgust first diverts rather than attracts attention. Accordingly, the N1 was smaller in a validly than in an invalidly disgust-cued condition. Furthermore, the frontal P3a for disgust, anger, and fear was found to be larger in the valid than in the invalid condition, which was interpreted as an involuntary switching of attention toward threat-related events to mobilize cognitive resources for action or defense. On the contrary, the parietal P3b only occurred at the conscious level; the enhanced P3b indicated that more cognitive resources were being allocated toward the task-relevant but previously less attended location, to ensure the effective achievement of task goals. In addition, group comparisons between individuals with low and high disgust sensitivity showed that the ERP differences between the disgust and the anger/fear conditions at the unconscious level may be attributed only to individuals with high disgust sensitivity. These findings, together with previous knowledge of the effects of fear and anger on attention, strengthen our confidence in the two-stage scheme of attentional modulation by threats, which consists of an early stage of bottom-up response scaling of sensory processing (reflected by the P1 and N1) and a later stage of top-down integration and regulation of emotion and behavior (reflected by the P3).     

Individual differences in the effect of smoking on frontal-central distribution of the CNV: Some observations on smokers' control of attentional behaviour

A previous investigation of individual differences in cortical activation during smoking reported differential development of vertex CNV ‘O’ and ‘E’ wave components in introverted and extraverted smokers. In the present paper the frontal CNV recorded from 12 extraverted and 12 introverted smokers was analysed under simple and choice foreperiod conditions during sham and real smoking. Smokers were matched for age, sex and neuroticism. Analysis of variance revealed significant group by smoking session effects for the later ‘E’ wave component but not for the early ‘O’ wave component. ‘O’ wave negativity though more prominent in frontal regions particularly in extraverts tended to be more affected by foreperiod conditions than smoking sessions. In general smoking produced an increase in central negativity in extraverts, and a decrease in parietal positivity in introverts. These results challenge the stimulus-related/response-related separation of smoking effects made previously to account for early and late CNV component differences. It is suggested that a distinction of CNV components in terms of input (sensory) and output (motor) aspects may anyway be inappropriate.An attempt is made to relate CNV negativity/positivity topography differences to a motor model of attentional strategies differentially deployed during smoking. Extraverted smoker strategies may aim to relieve boredom, enhance readiness to act and so increase central negativity. Introverts may smoke to inhibit distraction, maintain a complex attentional set, and so these affect parietal positivity.It is further suggested that the pharmacological effects of nicotine are those of a generalized mild stressor which supplement the motor aspects of smoking in inducing more motivated performance. Some further predictions concerning the effect of smoking on cortical activity are discussed.     

工作记忆对时间加工的影响

非时间信息加工与时间加工的关系是复杂的, 存在双向干扰或单向干扰, 结果的不一致与任务所需的注意资源及工作记忆都有关。工作记忆的中央执行系统在时间加工中起主要作用, 同时进行的非时间任务对中央执行功能的需求越多, 两种任务之间的干扰程度越大。语言环和视空间模板对时间加工的影响与非时间信息的类型有关。工作记忆作为一个整体以工作记忆容量为指标, 计时成绩也表现出与工作记忆容量有关的年龄、智力等方面的差异。时间加工和工作记忆在额叶、顶叶、基底神经节等皮质存在共同的神经机制。未来应该丰富工作记忆的研究内容, 结合时间加工的分段性探讨工作记忆影响时间加工的具体进程及神经机制, 并力求在应用方面取得一定的成果。