The Effects of Selective Attention on ERPs Elicited by Visual & Auditory Deviant Stimuli

本实验采用了视听双通道伪同时呈现的ｏｄｄｂａｌ模式,以汉字和简单几何图形为视觉刺激,１０００Ｈｚ和８００Ｈｚ的纯音为听觉刺激,使用注意通道（注意和非注意条件）×刺激概率（偏差刺激概率均为１５％,标准刺激的概率均为８５％）的２×２因素设计,来研究视觉和听觉偏差刺激在注意和非注意条件下诱发的事件相关电位（ＥＲＰｓ）。实验中视觉和听觉刺激随机序列地呈现给被试（刺激间隔ＩＳＩ为７００～１３００ｍｓ）,被试被要求注意某一通道如视觉通道,而相应地忽视另一通道即听觉通道,以左右手触键反应,如左手反应视觉偏差刺激,右手反应视觉标准刺激。结果表明,听觉偏差刺激在注意和非注意条件下均诱发了类似的不匹配负波（ＭＭＮ）;而视觉偏差刺激在注意和非注意条件下没有诱发ＭＭＮ或类似ＭＭＮ的成分,这是因为视觉系统的平行加工特性和难以对视觉影像产生记忆痕迹。听觉偏差刺激在注意条件下重迭了Ｎ２ｂ成分并跟随了Ｐ３ａ成分,这种重迭和跟随反映了选择注意中的定向反应。注意条件下听觉和视觉的偏差刺激诱发了较大波幅的Ｐ３００成分,反映了工作记忆中的表象更新。本实验的结果支持Ｎａａｔａｎｅｎ对ＭＭＮ所做的观察,听觉偏差刺激所诱发的ＭＭＮ与注意条件的无关性反映     

与飞行任务相关的认知负荷对听觉事件相关电位的影响

为研究与飞行任务相关的认知负荷对听觉事件相关电位的影响, 采用14名被试者开展飞行模拟实验, 完成基于不同认知负荷水平的仪表监视任务。同时, 由耳机双侧呈现oddball模式下的听觉刺激, 引导被试者关注飞行模拟任务, 忽略听觉刺激。记录听觉事件相关电位失匹配负波(mismatch negativity, MMN)、N1和P2作为认知负荷的评价指标。实验结果表明认知负荷对额叶MMN的影响显著, MMN平均波幅在高认知负荷下显著增强, 表明被试者对任务不相关信息的自动加工能力提高, 且MMN平均波幅与模拟飞行期间被试者对异常信息的正确探测率正相关。提示额中央区的MMN对于与飞行任务相关的认知负荷具有较好的敏感性, 并可能用于复杂飞行任务的认知负荷水平评价。但是, 实验结果也表明认知负荷对早期听觉成分N1, P2以及颞叶MMN的影响不明显, 在一定程度上说明了听觉事件相关电位在评价与飞行任务相关的认知负荷时所表现出的复杂效应。     

听觉条件下蒙古语元音和谐的偏侧化分析

文章研究记录了被试在无意识状态下(给被试播放无声无字幕电影,并要求被试忽略所听到的声音)感知蒙古语元音和谐的脑电数据,以探讨听觉条件下大脑对蒙古语元音和谐的ERP反映情况.对比不同变化条件下的脑电数据(蒙古语元音:和谐与不和谐;紧元音:和谐与不和谐;松元音:和谐与不和谐),以进行偏侧化实验.分析结果显示:1在听觉条件下,以Oddball范式呈现不和谐元音作为偏差刺激,和谐元音作为标准刺激.不管是紧元音、松元音还是蒙古语元音,均未诱发明显的MMN和P300.2被试感知刺激时所激活的脑区集中在额叶、中央区和颞叶.但感知强度有所不同,大脑对紧元音的感知强度相比松元音和蒙古语元音的要弱,而松元音和蒙古语元音的感知强度较为相近.     

基于ERP技术的数字界面布局认知与评估

为了探索用户对数字界面不同布局形式的比较和评估的认知过程,根据事件相关电位技术,采用较高相似度界面布局与较低相似度界面布局的Oddball实验范式,并结合脑电数据与行为数据,分析比较了2种相似度条件下N2b成分、P300成分的波幅和潜伏期变化情况.结果表明:在靶刺激认知早期阶段,N2b成分的波幅与靶刺激和标准刺激的偏差程度呈正相关关系;进入较深层次加工过程后,靶刺激所诱发的P300成分的波幅与靶刺激和标准刺激的相似程度呈正相关关系.研究结论可拓展应用于界面的迭代评估过程中,为实际项目中数字界面产品风格继承性评估提供重要的参考依据.     

冥想加工性别差异的神经机制 ——来自ERP的证据

采用事件相关电位(ERP)技术,记录52名大学生被试在听(正性和负性)冥想指导语的脑电波,探索冥想加工过程的神经机制与性别差异.以固定频率的声音作为线索诱发N2和P3成分,这2个成分作为探究刺激差异和注意力资源调配的标记分别在160 ms和240 ms的时间上观察到.结果表明:在正性冥想条件下,在前额叶皮层(PFC)中...     

年老化视空间注意脑机制的研究

采用“提示目标”的视觉实验范式，通过事件相关电位（ERP）技术研究了视觉注意年老化脑机制.青年和老年被试各16名；背景由3个同心黑色圆形线条组成，提示为大、中、小不等的3个圆圈组成，刺激材料是随机选取的大写英文字母，组成3个同心圆圈.不同范围圆圈提示时，靶刺激“T”出现在相对应的圆圈，而两个干扰刺激“T” 分别呈现在对侧视野的另外两个圆圈.要求被试人根据提示寻找效应圈的靶字母“T”，并尽快尽准确地按键判断出现在左视野还是右视野.结果显示干扰刺激的存在导致靶刺激识别难度增加，引起P1的增强和N1的降低；随着提示等级的增大，两组反应时均逐渐延长，早期ERP成分P1与N1波幅均减小；与青年组相比，老年组反应时更长，后部P1增强、N1抑制，且额区P2成分亦受到显著抑制.研究结果与年老化的“复杂度效应”一致；所发现老年组P2成分的显著抑制，提示年老化可能导致视觉空间注意（非随意注意）的前脑区功能缺陷.     

基于耳蜗行波理论的线性调频信号刺激听觉稳态反应研究

周期性短声(click)诱发的听觉稳态反应(ASSR)可用于临床测听与脑状态检测。该文研究一种基于耳蜗基底膜行波理论设计的线性调频声(chirp)诱发ASSR的方法。该方法以周期性的chirp声刺激人耳获得ASSR,比较了40Hz和90Hz下的chirp音与click音所获得ASSR在头皮分布、幅度的差异,并计算基于改进Rayleigh检测的ASSR检出率。结果表明:相同声压级下,chirp声比click能够诱发出更稳定、更高信噪比的ASSR,缩短检出时间,可替换click音在临床上应用。     

基于P300的脑-机接口: 视觉刺激强度对性能的影响

脑-机接口(BCI)是大脑与外部世界直接的交流通道.为了研究视觉刺激强度对基于P300的脑-机接口性能的影响,设计并实现了一种基于5个选择oddball的P300诱发电位范式的脑-机接口系统,并在此系统中研究2种不同强度下视觉刺激(高强度和低强度)下脑-机接口的信息传输率差异.9名受试者参加了实验,每位受试者在高低2种强度视觉刺激下各采集40组数据,数据在预处理后使用支持向量机进行分类,最终的目标识别率分别为84%和81%.平均波形表明在所设计的范式下2种强度视觉刺激均可以诱发出稳健的P300电位,离线分析表明高强度视觉刺激下平均信息传输率可以达到4.9 bit/min, 而低强度视觉刺激下为 4.5 bit/min.     

大脑对于外界刺激反应的EIT电压变化的研究

在探讨EIT技术工作原理的基础上,进行了大脑受到外界刺激反应的非侵入实验的实验方法研究及实验方案论证,根据大脑分别接受外界听觉和视觉刺激时所记录的实验数据,得出了不同电极对电流驱动情况下参考数据的变化曲线,听觉和视觉的EIT数据对应于参考数据的变化曲线,以及同一个测试对象在不同刺激(听觉和视觉)时的EIT电压变化曲线.通过对所得到的曲线进行比较、分析,发现了两种不同外界刺激下大脑电参数变化所引起的EIT电压变化的规律,为进一步实现EIT图像重构,分析大脑的活动规律奠定基础.     

内隐条件下性别对恐惧刺激加工的影响

采用内隐范式研究了性别差异对恐惧刺激加工的影响.实验一:在533张图片中选出50张图片,这些图片在唤醒度上是匹配的,但是在恐惧度和效价上是不匹配的;实验二:采用双向oddball范式,要求被试区分标准刺激和偏差刺激的内隐范式,研究性别差异对恐惧刺激加工的影响.结果发现:在内隐条件下,男性对中性刺激和恐惧刺激的反应时和正确率不存在显著差异,女性对恐惧刺激的反应显著快于对中性刺激的反应,且在正确率上对恐惧刺激的反应更加准确.女性对恐惧刺激的反应优势可能存在生物进化上的原因.     

Selective cortical representation of attended speaker in multi-talker speech perception

Humans possess a remarkable ability to attend to a single speaker's voice in a multi-talker background. How the auditory system manages to extract intelligible speech under such acoustically complex and adverse listening conditions is not known, and, indeed, it is not clear how attended speech is internally represented. Here, using multi-electrode surface recordings from the cortex of subjects engaged in a listening task with two simultaneous speakers, we demonstrate that population responses in non-primary human auditory cortex encode critical features of attended speech: speech spectrograms reconstructed based on cortical responses to the mixture of speakers reveal the salient spectral and temporal features of the attended speaker, as if subjects were listening to that speaker alone. A simple classifier trained solely on examples of single speakers can decode both attended words and speaker identity. We find that task performance is well predicted by a rapid increase in attention-modulated neural selectivity across both single-electrode and population-level cortical responses. These findings demonstrate that the cortical representation of speech does not merely reflect the external acoustic environment, but instead gives rise to the perceptual aspects relevant for the listener's intended goal.     

基于独立分量分析的失匹配负波快速提取

失匹配负波(MM N)是一种由刺激变化所诱发的听觉诱发电位成分,其过低的信噪比造成检测和提取比较困难。提出利用独立分量分析(ICA)方法对多导听觉诱发电位信号进行多次分解,根据MM N产生的生理机制及其信号特征,设计合理的独立分量选取原则,提取MM N。该方法通过仿真实验验证,能有效提高信噪比。在真实数据的处理中,仅用传统方法20%左右的实验时间,实现MM N成分波的提取。这将促进MM N在认知神经科学及临床上的应用。     

外源性注意不同线索提示比例对汉字数字SNARC效应的影响

采用Posner的线索实验范式,以判断数字奇偶为任务,材料为"壹"到"玖"的汉字数字,探讨外源性注意条件下不同线索提示比例对汉字数字SNARC效应的影响.结果发现:(1)当有效线索提示为80%时,注意和非注意条件下对汉字数字的加工均出现明显的SNARC效应,尽管在非注意条件下汉字数字出现明显的SNARC效应,但效应的趋...     

Visual behaviour mediated by retinal projections directed to the auditory pathway

An unresolved issue in cortical development concerns the relative contributions of intrinsic and extrinsic factors to the functional specification of different cortical areas. Ferrets in which retinal projections are redirected neonatally to the auditory thalamus have visually responsive cells in auditory thalamus and cortex, form a retinotopic map in auditory cortex and have visual receptive field properties in auditory cortex that are typical of cells in visual cortex. Here we report that this cross-modal projection and its representation in auditory cortex can mediate visual behaviour. When light stimuli are presented in the portion of the visual field that is 'seen' only by this projection, 'rewired' ferrets respond as though they perceive the stimuli to be visual rather than auditory. Thus the perceptual modality of a neocortical region is instructed to a significant extent by its extrinsic inputs. In addition, gratings of different spatial frequencies can be discriminated by the rewired pathway, although the grating acuity is lower than that of the normal visual pathway.     

Hearing visual motion in depth

Auditory spatial perception is strongly affected by visual cues. For example, if auditory and visual stimuli are presented synchronously but from different positions, the auditory event is mislocated towards the locus of the visual stimulus-the ventriloquism effect. This 'visual capture' also occurs in motion perception in which a static auditory stimulus appears to move with the visual moving object. We investigated how the human perceptual system coordinates complementary inputs from auditory and visual senses. Here we show that an auditory aftereffect occurs from adaptation to visual motion in depth. After a few minutes of viewing a square moving in depth, a steady sound was perceived as changing loudness in the opposite direction. Adaptation to a combination of auditory and visual stimuli changing in a compatible direction increased the aftereffect and the effect of visual adaptation almost disappeared when the directions were opposite. On the other hand, listening to a sound changing in intensity did not affect the visual changing-size aftereffect. The results provide psychophysical evidence that, for processing of motion in depth, the auditory system responds to both auditory changing intensity and visual motion in depth.     

Involuntary orienting to sound improves visual perception

To perceive real-world objects and events, we need to integrate several stimulus features belonging to different sensory modalities. Although the neural mechanisms and behavioural consequences of intersensory integration have been extensively studied, the processes that enable us to pay attention to multimodal objects are still poorly understood. An important question is whether a stimulus in one sensory modality automatically attracts attention to spatially coincident stimuli that appear subsequently in other modalities, thereby enhancing their perceptual salience. The occurrence of an irrelevant sound does facilitate motor responses to a subsequent light appearing nearby. However, because participants in previous studies made speeded responses rather than psychophysical judgements, it remains unclear whether involuntary auditory attention actually affects the perceptibility of visual stimuli as opposed to postperceptual decision and response processes. Here we provide psychophysical evidence that a sudden sound improves the detectability of a subsequent flash appearing at the same location. These data show that the involuntary orienting of attention to sound enhances early perceptual processing of visual stimuli.     

Feature-based attention influences motion processing gain in macaque visual cortex.

Changes in neural responses based on spatial attention have been demonstrated in many areas of visual cortex, indicating that the neural correlate of attention is an enhanced response to stimuli at an attended location and reduced responses to stimuli elsewhere. Here we demonstrate non-spatial, feature-based attentional modulation of visual motion processing, and show that attention increases the gain of direction-selective neurons in visual cortical area MT without narrowing the direction-tuning curves. These findings place important constraints on the neural mechanisms of attention and we propose to unify the effects of spatial location, direction of motion and other features of the attended stimuli in a 'feature similarity gain model' of attention.     

Gamma-band synchronization in visual cortex predicts speed of change detection

Our capacity to process and respond behaviourally to multiple incoming stimuli is very limited. To optimize the use of this limited capacity, attentional mechanisms give priority to behaviourally relevant stimuli at the expense of irrelevant distractors. In visual areas, attended stimuli induce enhanced responses and an improved synchronization of rhythmic neuronal activity in the gamma frequency band (40-70 Hz). Both effects probably improve the neuronal signalling of attended stimuli within and among brain areas. Attention also results in improved behavioural performance and shortened reaction times. However, it is not known how reaction times are related to either response strength or gamma-band synchronization in visual areas. Here we show that behavioural response times to a stimulus change can be predicted specifically by the degree of gamma-band synchronization among those neurons in monkey visual area V4 that are activated by the behaviourally relevant stimulus. When there are two visual stimuli and monkeys have to detect a change in one stimulus while ignoring the other, their reactions are fastest when the relevant stimulus induces strong gamma-band synchronization before and after the change in stimulus. This enhanced gamma-band synchronization is also followed by shorter neuronal response latencies on the fast trials. Conversely, the monkeys' reactions are slowest when gamma-band synchronization is high in response to the irrelevant distractor. Thus, enhanced neuronal gamma-band synchronization and shortened neuronal response latencies to an attended stimulus seem to have direct effects on visually triggered behaviour, reflecting an early neuronal correlate of efficient visuo-motor integration.     

Motion-induced blindness in normal observers.

Cases in which salient visual stimuli do not register consciously are known to occur in special conditions, such as the presentation of dissimilar stimuli to the two eyes or when images are stabilized on the retina. Here, we report a striking phenomenon of 'visual disappearance' observed with normal-sighted observers under natural conditions. When a global moving pattern is superimposed on high-contrast stationary or slowly moving stimuli, the latter disappear and reappear alternately for periods of several seconds. We show that this motion-induced blindness (MIB) phenomenon is unlikely to reflect retinal suppression, sensory masking or adaptation. The phenomenology observed includes perceptual grouping effects, object rivalry and visual field anisotropy. This is very similar to that found in other types of visual disappearance, as well as in clinical cases of attention deficits, in which partial invisibility might occur despite the primary visual areas being intact. Disappearance might reflect a disruption of attentional processing, which shifts the system into a winner-takes-all mode, uncovering the dynamics of competition between object representations within the human visual system.