错误加工的神经机制

错误加工在认知控制和行为监控中起着关键的作用。监控自己的认知和行为结果,觉察到应该的反应和实际的反应之间的差别（即错误）,纠正这种错误并防止再犯是错误加工的主要内容。错误反应或由代表反应错误等负性反馈刺激诱发的ERP相对于正确反应或由代表反应正确等正性反馈刺激诱发的ERP,表现出一个相对负走向的波形变化,称为错误相关负波（error-related negativity, ERN）和反馈相关负波（feedback-related negativity, FRN）,两者都定位于前扣回附近。错误加工神经机制的研究主要集中于前扣回与ERN、错误意识与错误加工、ERN与FRN的关系。对于前扣带回和ERN的功能意义的解释主要有错误检测理论、冲突监控理论、强化学习理论和预期违反假说。目前错误加工神经机制的研究在研究内容、研究方法和理论观点等方面还存在些问题,这些可能是未来进一步的研究方向     

时间信息自动加工与控制加工的电生理学指标

类时间信息加工的统一机制问题一直备受研究者关注。新近研究表明失匹配负波（MMN）是与时间信息自动加工有关的ERP成分,关联负变化（CNV）是与控制加工有关的ERP成分,而刺激遗漏电位（OSPs）既与自动加工又与控制加工有关。以三种ERP成分为指标的研究均为时间信息自动加工和控制加工的存在提供了可能的依据。未来研究不应该纠缠于自动加工和控制加工分界点的探究,而是着重从时间全程视角考察时距加工机制的特点。     

音乐训练对大脑前注意加工的影响

前注意加工(pre-attentive processing)是发生在注意之前不依赖于意识的一种认知过程, 它反映了大脑对刺激的无意识的、自动的加工。失匹配负波(mismatch negativity, MMN)是研究前注意加工最常用的指标。MMN波幅降低已成为精神分裂症、抑郁症等精神类疾病的重要临床指征。MMN的研究范式主要包括经典oddball范式和多特征范式等。音乐训练对于人脑结构和功能有重要的影响, 对于增加灰质体积、改善注意记忆功能都有着显著的功效。音乐训练对MMN也有显著影响, 并表现在由各类声音特征构建的范式上。未来研究应进一步比较东西方音乐对MMN的影响, 探索更具生态化效度的研究范式, 揭示音乐训练对老年人MMN的影响及机制。     

早期视听整合加工——来自MMN的证据

视听整合是指当呈现的视觉和听觉信号在时间、空间上大致接近时,视觉和听觉系统倾向于整合的加工过程。失匹配负波(Mismatch Negativity,MMN)作为反映大脑早期加工的成分,表征偏差的信息输入与感觉记忆痕迹之间的神经失匹配。以MMN作为探测指标的视听整合加工研究,主要包括MMN在阅读理解中字母和语音、韵律信息、麦格克效应等方面的视听整合加工,以及分析跨通道视听整合相互竞争、相互补充的关系。未来研究需聚焦于其他通道的跨通道整合加工,同时应拓展MMN的诱发范式。     

错误相关负波（ERN）在精神病理学研究中的应用

错误相关负波（error-related negativity, ERN）是由行为错误诱发的一种脑电波成分,最大峰值在错误反应之后的50ms左右,偶极子源定位于前扣带回（anterior cingulate cortex, ACC）附近。错误加工（error processing）的经典研究范式中出现的ERN成分可能反映了ACC具有错误检测、冲突监控、强化学习、情绪动机等功能。大量研究表明过度的和不足的错误相关脑活动（hyperactive and hypoactive error processing）可能分别与精神病理学的内化性和外化性障碍（internalizing and externalizing disorders）相关联。内化性和外化性障碍的内表型（endophenotype）的研究,还存在许多值得进一步探索的问题。     

概率贴现和时间贴现在人脑中的分离

本研究运用ERP技术来检验概率贴现和时间贴现是否反映了相同的神经机制过程。在本研究中,我们在一个刺激中同时操纵概率贴现（风险vs.安全）和时间贴现（1个月后vs.今天）水平。通过对两个过程上的ERN以及全时间段的ERP分析来确定它们是否反映了相同的认知过程。结果发现,这两者在ERN上存在差异,同时这两个效应在ERP的时程和出现的电极点上都存在差异。这些差异表明这两者可能包含着不同的神经机制过程。     

错误相关负波的神经起源及其影响因素

与个体做出错误反应相伴的错误相关ERP成分叫错误相关负波 (error-related negativity, ERN),当前冲突监控理论、表征失匹配理论和强化学习理论从不同的角度对ERN的神经机制进行解释,各理论间并非完全相互排斥。目前大部分研究认为ERN定位于扣带回,部分研究则出现其它脑区的激活,然而,扣带回与其它脑区存在复杂的神经功能联系,ERN 电位很可能是多个脑区电活动在头颅的综合表现,而非某一脑区的单独表现。ERN的神经机制受到实验任务、被试年龄及其意识水平等因素的影响。未来要推动实验室研究走向临床应用,发现与诊断脑电波异常的病人和毒品易复吸人群。     

反馈相关负波与社会关系认知

反馈相关负波(feedback-related negativity, FRN)是人类进行结果评价时诱发的一个重要的脑电负成分, 出现在反馈刺激后200~300ms间。作为社会认知研究的可视化指标和工具, 它在社会关系认知中有着十分重要的作用。研究从社会关系与反映并表征社会关系的社会规范两方面阐述了反馈相关负波在社会关系认知中的作用。前者着重阐述了反馈相关负波在作为独立个体所扮演的社会角色和人际关系中的作用, 后者主要介绍了反馈相关负波在分配公平和责任规范中的作用。未来研究需进一步联合其他脑电成分(如P300), 采用更严密的实验设计和研究范式来探讨不同人际亲密度个体在责任分摊过程中的认知神经过程及其在独立担责情况下责任绝对额度对其结果评价和社会关系认知的影响。     

发展性协调障碍儿童视觉通道前注意加工的特点：来自ERP的证据

研究表明发展性协调障碍儿童听觉通道的前注意受损,其视觉通道的前注意加工是否也存在缺陷,从而造成了信息加工困难,目前尚不清楚。本研究旨在探究发展性协调障碍儿童视觉通道前注意加工的特点。从小学二、三、四年级共760名学生中筛选出障碍组20名,同时选择年龄、智力水平相当的对照组儿童20名。采用非注意Oddball任务,以不同颜色图片为实验材料,比较两组儿童前注意信息加工能力。行为结果表明,在注意主任务上,两组儿童的反应时不存在差异;然而,障碍组儿童的准确率显著低于对照组。ERP结果表明,相比于对照组儿童,障碍组儿童的视觉失匹配负波(visual mismatch negativity, vMMN)潜伏期明显延长。同时,本研究还发现运动技能诊断量表得分与vMMN的潜伏期存在显著相关。结果提示,发展性协调障碍儿童视觉通道前注意加工可能存在缺陷;vMMN潜伏期可作为初步评估和判断发展性协调障碍的脑电指标。     

从ERP研究看前瞻记忆的神经基础和认知加工机制

关于前瞻记忆的ERP研究主要关注两个方面：神经基础和认知加工机制。神经基础方面的研究发现：前瞻记忆诱发了两种特异性的ERP成分—— N300和前瞻性正波; 前瞻记忆与回溯性记忆的神经基础有相似又有不同; 老年人的前瞻记忆可能存在一种不同于年轻人的神经机制。认知加工机制方面的研究主要为前瞻记忆的预备注意加工和记忆加工理论提供了ERP方面的证据支持。     

Atypical central auditory speech-sound discrimination in children who stutter as indexed by the mismatch negativity

PurposeRecent theoretical conceptualizations suggest that disfluencies in stuttering may arise from several factors, one of them being atypical auditory processing. The main purpose of the present study was to investigate whether speech sound encoding and central auditory discrimination, are affected in children who stutter (CWS).MethodsParticipants were 10 CWS, and 12 typically developing children with fluent speech (TDC). Event-related potentials (ERPs) for syllables and syllable changes [consonant, vowel, vowel-duration, frequency (F0), and intensity changes], critical in speech perception and language development of CWS were compared to those of TDC.ResultsThere were no significant group differences in the amplitudes or latencies of the P1 or N2 responses elicited by the standard stimuli. However, the Mismatch Negativity (MMN) amplitude was significantly smaller in CWS than in TDC. For TDC all deviants of the linguistic multifeature paradigm elicited significant MMN amplitudes, comparable with the results found earlier with the same paradigm in 6-year-old children. In contrast, only the duration change elicited a significant MMN in CWS.ConclusionsThe results showed that central auditory speech-sound processing was typical at the level of sound encoding in CWS. In contrast, central speech-sound discrimination, as indexed by the MMN for multiple sound features (both phonetic and prosodic), was atypical in the group of CWS. Findings were linked to existing conceptualizations on stuttering etiology.Educational objectives: The reader will be able (a) to describe recent findings on central auditory speech-sound processing in individuals who stutter, (b) to describe the measurement of auditory reception and central auditory speech-sound discrimination, (c) to describe the findings of central auditory speech-sound discrimination, as indexed by the mismatch negativity (MMN), in children who stutter.     

Early and late mismatch negativity elicited by words and speech-like stimuli in children

In auditory perception the brain's attentional and preattentional mechanisms select certain stimuli for preferential processing and filter out irrelevant input. This study investigated nonattentive auditory processing in children. Event-related potentials (ERPs) provide a means to study neural correlates related to language and speech-sound processing. Mismatch negativity (MMN) is an ERP wave that indicates attention-independent perceptual change detection. In this study cortical ERPs were elicited by complex tones, naturally spoken words, and pseudowords, with each stimulus type containing equal acoustical elements. Tones elicited a bifurcated mismatch negativity (MMN), with early MMN (peaking at 150-200 ms) being more dominant. On the other hand, words elicited a strong late MMN, peaking at about 400-450 ms after stimulus onset. The MMN wave form was significantly weaker for pseudowords than for words. The late MMN wave, especially for word differences, was found to reflect summating MMN generators and memory trace formation on gestalt bases. Results suggest that the auditory processing, even nonattended, is highly associated with the cognitive meaning of the stimuli.     

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。     

Measurement and interpretation of the mismatch negativity

The mismatch negativity (MMN) is a preattentive brain response elicited by changes in repetitive auditory stimulation. Usually, it is identified as the difference between the event-related potential elicited by a high-probabilitystandard and that elicited by a low-probabilitydeviant stimulus. Most likely, MMN is generated by the outcome of a comparison process that registers a difference between the neural representation of the actual input and the memory trace of the standard stimulation. Since its discovery by Näätänen and colleagues in 1978, MMN has become a useful tool for investigating the brain’s auditory information processing in several hundred studies. The present paper describes problems related to the measurement and interpretation of MMN. First, it reviews important features of MMN. Second, it provides technical information about recording and parametrization of this brain wave. Third, it discusses various methodological aspects which may be taken into account in the designing of MMN experiments. Fourth, it addresses some conceptual problems that have to be considered in the proper interpretation of MMN.     

Event-related brain potentials reflect traces of echoic memory in humans

In sequences of identical auditory stimuli, infrequent deviant stimuli elicit an event-related brain potential component called mismatch negativity (MMN). MMN is presumed to reflect the existence of a memory trace of the frequent stimulus at the moment of presentation of the infrequent stimulus. This hypothesis was tested by applying the recognition-masking paradigm of cognitive psychology. In this paradigm, a masking sound presented shortly before or after a test stimulus diminishes the recognition memory of this stimulus, the more so the shorter the interval between the test and masking stimuli. This interval was varied in the present study. It was found that the MMN amplitude strongly correlated with the subject’s ability to discriminate between frequent and infrequent stimuli. This result strongly suggests that MMN providesa measure for a trace of sensory memory, and further, that with MMN, this memory can be studied without performance-related distortions.     

Electrophysiological evidence for age effects on sensory memory processing of tonal patterns

In older adults, difficulties processing complex auditory scenes, such as speech comprehension in noisy environments, might be due to a specific impairment of temporal processing at early, automatic processing stages involving auditory sensory memory (ASM). Even though age effects on auditory temporal processing have been well-documented, there is a paucity of research on how ASM processing of more complex tone-patterns is altered by age. In the current study, age effects on ASM processing of temporal and frequency aspects of two-tone patterns were investigated using a passive listening protocol. The P1 component, the mismatch negativity (MMN) and the P3a component of event-related brain potentials (ERPs) to tone frequency and temporal pattern deviants were recorded in younger and older adults as a measure of auditory event detection, ASM processing, and attention switching, respectively. MMN was elicited with smaller amplitude to both frequency and temporal deviants in older adults. Furthermore, P3a was elicited only in the younger adults. In conclusion, the smaller MMN amplitude indicates that automatic processing of both frequency and temporal aspects of two-tone patterns is impaired in older adults. The failure to initiate an attention switch, suggested by the absence of P3a, indicates that impaired ASM processing of patterns may lead to less distractibility in older adults. Our results suggest age-related changes in ASM processing of patterns that cannot be explained by an inhibitory deficit.     

Input to verbal working memory: Preattentive construction of the central speech representation

Working memory uses central sound representations as an informational basis. The central sound representation is the temporally and feature-integrated mental representation that corresponds to phenomenal perception. It is used in (higher-order) mental operations and stored in long-term memory. In the bottom-up processing path, the central sound representation can be probed at the level of auditory sensory memory with the mismatch negativity (MMN) of the event-related potential. The present paper reviews a newly developed MMN paradigm to tap into the processing of speech sound representations. Preattentive vowel categorization based on F1-F2 formant information occurs in speech sounds and complex tones even under conditions of high variability of the auditory input. However, an additional experiment demonstrated the limits of the preattentive categorization of language-relevant information. It tested whether the system categorizes complex tones containing the F1 and F2 formant components of the vowel /a/ differently than six sounds with nonlanguage-like F1-F2 combinations. From the absence of an MMN in this experiment, it is concluded that no adequate vowel representation was constructed. This shows limitations of the capability of preattentive vowel categorization.     

The auditory sensory memory trace decays rapidly in newborns

The present study investigated the temporal dynamics of auditory sensory memory in newborns as reflected by the mismatch negativity (MMN), a preattentive electric change-detection response. MMN was obtained from 24 full-term healthy newborns who were either awake or asleep (quiet or active sleep) during the experiments. Stimuli were 1,000 Hz tones (standards) that were occasionally replaced by 1,100 Hz tones (deviants). The constant stimulus onset asynchrony (SOA) was, in separate blocks, either 450, 800, or 1,500 ms. A prominent MMN was obtained at the 800 ms SOA in all three sleep or waking states, whereas no MMN occurred at 450 and 1,500 ms SOAs. In view of the fact that in adults MMN is elicited even with a 10s SOA, these results imply that the time span of auditory memory is considerably shorter in neonates than in adults and 8-12-year-old children.     

Effects of visual attentional load on low-level auditory scene analysis

The sharing of processing resources between the senses was investigated by examining the effects of visual task load on auditory event-related brain potentials (ERPs). In Experiment 1, participants completed both a zero-back and a one-back visual task while a tone pattern or a harmonic series was presented. N1 and P2 waves were modulated by visual task difficulty, but neither mismatch negativity (MMN) elicited by deviant stimuli from the tone pattern nor object-related negativity (ORN) elicited by mistuning from the harmonic series was affected. In Experiment 2, participants responded to identity (what) or location (where) in vision, while ignoring sounds alternating in either pitch (what) or location (where). Auditory ERP modulations were consistent with task difficulty, rather than with task specificity. In Experiment 3, we investigated auditory ERP generation under conditions of no visual task. The results are discussed with respect to a distinction between process-general (N1 and P2) and processspecific (MMN and ORN) auditory ERPs.     

The influence of dichotical fusion on the redundant signals effect,localization performance,and the mismatch negativity

In two experiments, each including a simple reaction time (RT) task, a localization task, and a passive oddball paradigm, the physical similarity between two dichotically presented auditory stimuli was manipulated. In both experiments, a redundant signals effect (RSE), high localization performance, and a reliable mismatch negativity (MMN) was observed for largely differing stimuli, suggesting that these are coded separately in auditory memory. In contrast, no RSE and a localization rate close to chance level (experiment 1) or at chance (experiment 2) were observed for stimuli differing to a lesser degree. Crucially, for such stimuli a small (experiment 1) or no (experiment 2) MMN were observed. These MMN results indicate that such stimuli tend to fuse into a single percept and that this fusion occurs rather early within information processing.