神经振荡影响快速言语识别的时间瓶颈

大脑可以快速地加工信息以应对不断变化的环境,其典型范例之一是快速言语识别。自然言语的瓶颈速率约为8～12音节/秒,与神经振荡的alpha速率相近。此外,已有研究表明alpha振荡可以调控知觉过程的时间分辨率。那么,alpha振荡速率是否影响快速言语识别的时间瓶颈？其作用机制是什么？本研究利用心理物理学方法和认知神经科学方法,从现象和机制两个方面考察alpha振荡如何影响快速言语识别的时间瓶颈。在现象方面,本研究将验证快速言语识别的时间瓶颈与alpha振荡速率的一致性。在机制方面,本研究将研究alpha振荡速率如何影响快速言语识别的行为表现,又如何调控大脑对言语信号的神经加工过程。本研究希望找到快速言语识别的神经机制,从而更深入地理解大脑的快速加工过程,并进一步探讨神经振荡调控大脑时间分辨率的相关机制。     

经颅电刺激与视功能调控

经颅电刺激(Transcranial Electrical Stimulation, TES)通过电极将特定模式的低强度电流作用于大脑头皮以调控皮层活动, 是一种非侵入、无创的神经刺激方法。根据刺激电流的模式的不同, TES分为经颅直流电刺激(tDCS), 经颅交流电刺激(tACS)和经颅随机电刺激(tRNS)。TES能对视功能诸如光幻视阈值、视野、对比敏感度、视知觉运动等进行一定程度上的调控, 并且能够与传统的视觉知觉学习训练相结合以调控视觉功能。对于不同的视觉功能, 不同的TES参数和模式的调控效果有所不同。     

面孔表情和声音情绪信息整合加工的脑机制

在现实生活中, 有效的情绪识别往往依赖于不同通道间的信息整合(如, 面孔、声音)。本文梳理相关研究认为, 面孔表情和声音情绪信息在早期知觉阶段即产生交互作用, 且初级感知觉皮层负责两者信息的编码; 而在晚期决策阶段, 杏仁核、颞叶等高级脑区完成对情绪信息内容的认知评估整合; 此外, 神经振荡活动在多个频段上的功能耦合促进了跨通道情绪信息整合。未来研究需要进一步探究两者整合是否与情绪冲突有关, 以及不一致的情绪信息在整合中是否有优势, 探明不同频段的神经振荡如何促进面孔表情和声音情绪信息整合, 以便更深入地了解面孔表情和声音情绪信息整合的神经动力学基础。     

工作记忆的神经振荡调控：基于神经振荡夹带现象

工作记忆的神经振荡机制研究是当前记忆领域的研究热点之一。那么, 神经振荡仅仅是工作记忆过程的伴随现象, 还是直接参与并调控了工作记忆的加工过程?已有研究发现, 大脑内部的神经振荡活动在外界节律性刺激的驱动下, 逐步与外界刺激节律相位同步化, 这一现象被称为“神经振荡夹带”。重复经颅磁刺激(repetitive Transcranial Magnetic Stimulation, rTMS)和经颅交流电刺激(transcranial Alternating Current Stimulation, tACS)干预研究基于此现象, 对大脑局部脑区施加节律性磁、电刺激, 进而调控工作记忆过程中特定频段的神经振荡活动、跨频段的神经振荡耦合或跨脑区的神经振荡相位同步, 为神经振荡参与工作记忆加工提供较为直接的因果证据。未来研究需考虑从脑网络的角度出发, 调控多个脑区之间的神经振荡活动, 进一步考察神经振荡对工作记忆的影响。此外, 还需注意探索和优化rTMS/tACS调控工作记忆的刺激方案, 并辅以客观的脑电记录, 提高该类研究的有效性和可重复性, 最终达到提高工作记忆能力的目的。     

左侧眶额皮层在自动情绪调节下注意选择中的作用：来自经颅直流电刺激的证据

前人研究表明自动情绪调节能够自上而下地影响情绪及情绪性注意过程。近来有研究提示自动情绪调节与眶额皮层(orbitofrontal cortex, OFC)有关。也有研究表明左侧OFC的激活影响负性注意偏向。本研究采用经颅直流电刺激技术, 考察阈下启动情绪控制目标条件下, 抑制左侧眶额皮层兴奋性是否影响负性注意偏向。结果发现, 使用阴极刺激抑制左侧OFC活动可以加快被试对与恐惧刺激位置一致的探测点的反应。该结果提示左侧眶额皮层是自动情绪调节下情绪性注意选择相关的重要脑区。     

创造力产生过程中的神经振荡机制

创造力究竟是怎么产生的, 目前尚未得出一致的结论。神经电生理技术因其高时间分辨率, 可以准确地揭示创造力产生进程中的神经振荡机制, 从而帮助人们更深刻地理解创造力的本质。近年来的研究发现, 单节律alpha神经振荡会随着创造力的增加而增强, 这反映了创造力产生过程中的内部信息加工需求增加、自上而下的抑制控制增强。同时, 多频段神经振荡交叉节律耦合体现了创造性产生过程中额叶、颞叶和顶叶等多脑区之间信息交流的动态变化。未来研究应该以整合理论框架为基础, 结合多层次多方法的研究工具, 引进更生态化的数理计算方法, 并利用计算神经科学建模来预测个体创造力发展趋势, 从而全面深刻地认识创造力的本质。     

未意识到错误影响错误后调整的电生理证据

现有研究一致认为意识到错误可引起错误后调整, 但是未意识到错误能否促使个体进行错误后调整尚存争议。本实验采用基于go/no-go范式的错误意识任务考察上述问题, 并根据被试对自己按键反应正误主观报告将no-go错误反应分为意识到错误和未意识到错误。行为结果发现, 意识到错误和未意识到错误后正确率均显著高于正确击中试次(正确go试次)后正确率; 但是, 意识到错误后试次反应时显著快于正确击中后反应时, 未意识到错误后反应时显著慢于正确击中后反应时。该结果表明两类错误均优化了错误后行为表现, 但是意识到错误后被试调整速度加快, 未意识到错误后被试调整速度减慢。进而, 时频分析发现意识到错误相较于未意识到错误诱发显著更强的alpha波能量。并且, 前者在错误意识主观报告前已诱发alpha波, 后者在错误意识主观报告反应后诱发alpha波。该结果表明意识到错误一直处于持续的注意监控中, 而未意识到错误是任务引起的暂时注意控制。因此, 本实验说明错误意识影响错误后调整, 意识到错误可能采用类似主动性控制的策略调节错误后行为, 而未意识到错误可能采用类似反应性控制的策略调节错误后行为。     

知觉启动效应及其脑机制的研究进展

该文从三个方面对知觉启动效应研究进行了回顾：(1)知觉启动的一般特征：(2)刺激的物理特征与知觉启动之间的关系;(3)知觉启动的神经解剖基础及神经机制。该文指出．知觉启动主要加工刺激表面的物理特征;刺激的大小、位置、颜色、模式等特征尽管对知觉启动有影响．但刺激的形状和结构等特征对于知觉启动更重要;知觉启动主要受枕部皮层的调节。最后,讨论了几个有关知觉启动机制的理论假说。     

经颅直流电刺激对健康大学生反应抑制的影响

拟观察经颅直流电刺激作用于右侧背外侧前额叶皮层前后,被试在停止信号任务中的行为变化。实验共入组34名正常大学生,被试前后两次随机接受真刺激和伪刺激,两次刺激间隔7天,每个被试在接受刺激前后均完成停止信号任务,并在每次实验前后完成Stroop色词任务、词语流畅性、数字广度任务。结果发现真刺激作用于右侧背外侧前额叶皮层后停止信号反应时显著减小,但伪刺激条件下没有该趋势。本实验证明了作用于右侧背外侧前额叶皮层的经颅直流电刺激可以调节反应抑制能力,右侧背外侧前额叶皮层是反应抑制的重要脑区。     

汉语母语儿童和成人视听双通道英语语音知觉的训练研究

本研究通过前测-训练-后测的实验程序,对22名五年级小学生和29名大学一年级学生在不同测查条件下知觉英语辅音/s/和/θ/的可塑性情况进行了考察和比较。两个年龄阶段被试在前后测中均接受纯听、视听一致、视听不一致和纯视条件下的测查,训练时两个年龄阶段被试中分别有一半接受纯听训练,另一半接受视听训练,训练时间历时10天,每天30分钟左右。对训练效果的分析发现:(1)接受纯听和视听训练的五年级学生在纯视测查条件下知觉英语辅音/s/和/θ/的提高率有显著差异,视听训练被试显著高于纯听训练被试,在其他条件下没有显著差异;(2)接受两种训练的大学生在所有条件下知觉英语辅音/s/和/θ/的提高率都没有显著差异。说明儿童表现出了更强的视听双通道语音知觉的可塑性。     

Prestimulus alpha-band power biases visual discrimination confidence,but not accuracy

The magnitude of power in the alpha-band (8–13 Hz) of the electroencephalogram (EEG) prior to the onset of a near threshold visual stimulus predicts performance. Together with other findings, this has been interpreted as evidence that alpha-band dynamics reflect cortical excitability. We reasoned, however, that non-specific changes in excitability would be expected to influence signal and noise in the same way, leaving actual discriminability unchanged. Indeed, using a two-choice orientation discrimination task, we found that discrimination accuracy was unaffected by fluctuations in prestimulus alpha power. Decision confidence, on the other hand, was strongly negatively correlated with prestimulus alpha power. This finding constitutes a clear dissociation between objective and subjective measures of visual perception as a function of prestimulus cortical excitability. This dissociation is predicted by a model where the balance of evidence supporting each choice drives objective performance but only the magnitude of evidence supporting the selected choice drives subjective reports, suggesting that human perceptual confidence can be suboptimal with respect to tracking objective accuracy.     

Rescuing stimuli from invisibility: Inducing a momentary release from visual masking with pre-target entrainment

At near-threshold levels of stimulation, identical stimulus parameters can result in very different phenomenal experiences. Can we manipulate which stimuli reach consciousness? Here we show that consciousness of otherwise masked stimuli can be experimentally induced by sensory entrainment. We preceded a backward-masked stimulus with a series of rapid visual events presented at 12 Hz for 800 ms. Peaks in visual sensitivity (d′) were observed when the target appeared at the time that the next entraining stimuli would have occurred. Observers’ sensitivity for identical masked near-threshold stimuli increased by factors as large as 55%, but only at this precise moment in time. These data thus reveal that awareness of near-threshold stimuli can be manipulated by entrainment to rhythmic events, supporting the functional role of induced oscillations in underlying cortical excitability, and suggest a plausible mechanism of temporal attention.     

Awareness in the crowd: Beta power and alpha phase of prestimulus oscillations predict object discrimination in visual crowding

Visual crowding is among the factors that most hamper conscious object perception. However, we currently ignore the neural states that predispose to an accurate perception within different crowding regimes. Here, we performed single-trial analyses of the electroencephalographical (EEG) oscillations, evaluating the prestimulus power and phase differences between correct and incorrect discrimination during a letter-crowding task, where irrelevant letters were placed nearby (strong crowding) or far (mid crowding) relative to the target. Results show that prestimulus alpha (8–12 Hz) power was related to target discrimination in the mid, but not in the strong, crowding condition. Importantly, accurate discrimination in the strong crowding condition was predicted by the phase of alpha and by the power of beta (13–20 Hz) oscillations. These evidence suggest that both periodic visual sampling mechanisms, reflected in the alpha phase, and network predisposition to extract local information, reflected in the beta power, predispose to object discrimination in a crowded scene.     

Perceptual load alters visual excitability

Increasing perceptual load reduces the processing of visual stimuli outside the focus of attention, but the mechanism underlying these effects remains unclear. Here we tested an account attributing the effects of perceptual load to modulations of visual cortex excitability. In contrast to stimulus competition accounts, which propose that load should affect simultaneous, but not sequential, stimulus presentations, the visual excitability account makes the novel prediction that load should affect detection sensitivity for both simultaneous and sequential presentations. Participants fixated a stimulus stream, responding to targets defined by either a color (low load) or color and orientation conjunctions (high load). Additionally, detection sensitivity was measured for a peripheral critical stimulus (CS) presented occasionally. Increasing load at fixation reduced sensitivity to the peripheral CSs; this effect was similar regardless of whether CSs were presented simultaneously with central stimuli or during the (otherwise empty) interval between them. Controls ruled out explanations of the results in terms of strategic task prioritization. These findings support a cortical excitability account for perceptual load, challenging stimulus competition accounts.     

Effect of luminance on perceptual alternation of ambiguous patterns

The perceptual alternation of the Necker cube, in its stationary phase, is studied as a function of the stimulus luminance down to the extreme condition in which the cones are completely inactivated so that the pattern of neural excitation reaching the primary visual cortex is very different from the normal one. No evident effect of luminance was found under passive observation either on the reversal rate or on the features of data distributions. Moreover, the complementary situation in which perception is based only on the cones does not affect the phenomenon either. These results permit the assumption that the perceptual alternation in its stationary phase, is a passive and automatic process, that is affected neither by a satiation of the first levels of the visual system nor by the psychological attitude of the subject consequent on dazzling the retina.     

State and complexity-dependent symmetry identification of 2-dimensional patterns and evoked potentials

To analyse the influence of structural complexity of visual patterns and of an operationally defined cognitive state on evoked potentials some on--line closed--loop experiments were carried out. Symmetrical checkerboard patterns generated by means of Walsh functions were used as stimuli. The inherent symmetry should be recognized by the subjects. The state was defined on the basis of the spectral power density distribution of the EEG measured in the time interval of one second before the stimulus onset. The two state values were labeled by the state of alpha wave dominance and the state of non alpha wave dominance. According to the definition for the state of alpha wave dominance 70% of the whole spectral power must be contained in the frequency range from 8 Hz until 13 Hz at least. Otherwise the prestimulus EEG are labeled by the concept of non alpha wave state. The influence of the cognitive state and of the structural complexity on the evoked potentials has been verified experimentally. Significantly higher amplitudes of the evoked potentials in the time range of 140 ms until 200 ms after stimulus onset are due to higher complexity of the stimuli. The state of alpha wave dominance led to significantly stronger negativity of the evoked potentials in the range of 280 ms until 400 ms after stimulus onset.     

Dynamics of alpha oscillations elucidate facial affect recognition in schizophrenia

Impaired facial affect recognition is characteristic of schizophrenia and has been related to impaired social function, but the relevant neural mechanisms have not been fully identified. The present study sought to identify the role of oscillatory alpha activity in that deficit during the process of facial emotion recognition. Neuromagnetic brain activity was monitored while 44 schizophrenia patients and 44 healthy controls viewed 5-s videos showing human faces gradually changing from neutral to fearful or happy expressions or from the neutral face of one poser to the neutral face of another. Recognition performance was determined separately by self-report. Relative to prestimulus baseline, controls exhibited a 10- to 15-Hz power increase prior to full recognition and a 10- to 15-Hz power decrease during the postrecognition phase. These results support recent proposals about the function of alpha-band oscillations in normal stimulus evaluation. The patients failed to show this sequence of alpha power increase and decrease and also showed low 10- to 15-Hz power and high 10- to 15-Hz connectivity during the prestimulus baseline. In light of the proposal that a combination of alpha power increase and functional disconnection facilitates information intake and processing, the finding of an abnormal association of low baseline alpha power and high connectivity in schizophrenia suggests a state of impaired readiness that fosters abnormal dynamics during facial affect recognition.     

Concurrent processing of spatial relations and objects in two cerebral hemispheres

This study examined hemispheric asymmetry for concurrent processing of object and spatial information. Participants viewed two successive stimuli, each of which consisted of two digits and two pictures that were randomly located and judged them as identical or different. A sample stimulus was presented in a central visual field, followed by a matching stimulus presented briefly in a left or right visual field. The matching stimuli were different from the sample stimuli with respect to the object (digit or picture) or spatial (locations or distances of items) aspect. No visual field asymmetry was found in the detection of object change. However, a left visual field advantage was found in the detection of spatial change. This result can be explained by the double filtering by frequency theory of Ivry and Robertson, who asserted that the left hemisphere has a bias for processing information contained in relatively high spatial frequencies whereas the right hemisphere has a bias for processing information contained in relatively low spatial frequencies. Based upon this evidence, the importance of interhemispheric integration for visual scene perception is discussed.     

Electrophysiological evidence for a shared representational medium for visual images and visual percepts

Does mental imagery involve the activation of representations in the visual system? Systematic effects of imagery on visual signal detection performance have been used to argue that imagery and the perceptual processing of stimuli interact at some common locus of activity (Farah, 1985). However, such a result is neutral with respect to the question of whether the interaction occurs during modality-specific visual processing of the stimulus. If imagery affects stimulus processing at early, modality-specific stages of stimulus representation, this implies that the shared stimulus representations are visual, whereas if imagery affects stimulus processing only at later, amodal stages of stimulus representation, this implies that imagery involves more abstract, postvisual stimulus representations. To distinguish between these two possibilities, we repeated the earlier imagery-perception interaction experiment while recording event-related potentials (ERPs) to stimuli from 16 scalp electrodes. By observing the time course and scalp distribution of the effect of imagery on the ERP to stimuli, we can put constraints on the locus of the shared representations for imagery and perception. An effect of imagery was seen within 200 ms following stimulus presentation, at the latency of the first negative component of the visual ERP, localized at the occipital and posterior temporal regions of the scalp, that is, directly over visual cortex. This finding provides support for the claim that mental images interact with percepts in the visual system proper and hence that mental images are themselves visual representations.     

Anticipation across modalities in children and adults: Relating anticipatory alpha rhythm lateralization,reaction time,and executive function

The development of the ability to anticipate—as manifested by preparatory actions and neural activation related to the expectation of an upcoming stimulus—may play a key role in the ontogeny of cognitive skills more broadly. This preregistered study examined anticipatory brain potentials and behavioral responses (reaction time; RT) to anticipated target stimuli in relation to individual differences in the ability to use goals to direct action (as indexed by measures of executive function; EF). A cross-sectional investigation was conducted in 40 adults (aged 18–25 years) and 40 children (aged 6–8 years) to examine the association of changes in the amplitude of modality-specific alpha-range rhythms in the electroencephalogram (EEG) during anticipation of lateralized visual, tactile, or auditory stimuli with inter- and intraindividual variation in RT and EF. Children and adults exhibited contralateral anticipatory reductions in the mu rhythm and the visual alpha rhythm for tactile and visual anticipation, respectively, indicating modality and spatially specific attention allocation. Variability in within-subject anticipatory alpha lateralization (the difference between contralateral and ipsilateral alpha power) was related to single-trial RT. This relation was more prominent in adults than in children, and was not apparent for auditory stimuli. Multilevel models indicated that interindividual differences in anticipatory mu rhythm lateralization contributed to the significant association with variability in EF, but this was not the case for visual or auditory alpha rhythms. Exploratory microstate analyses were undertaken to cluster global field power (GFP) into a distribution-free temporal analysis examining developmental differences across samples and in relation to RT and EF. Anticipation is suggested as a developmental bridge construct connecting neuroscience, behavior, and cognition, with anticipatory EEG oscillations being discussed as quantifiable and potentially malleable indicators of stimulus prediction.