幼儿视觉ERP：Ⅱ．P_3潜伏期和反应时间

幼儿事件相关电位（ＥＲＰ）对研究儿童心理发展有重要意义，因试验难度大，国内外至今未见报道。本研究以４～５岁幼儿为研究对象，用母亲照片和陌生女人照片按一定概率编排成刺激序列，分别在三个试验中成功诱发ＥＲＰ。结果证明幼儿Ｐ３平均潜伏期符合成人Ｐ３定义范围；幼儿Ｐ３潜伏期Ｆｚ长于Ｐｚ、Ｏｚ；无任务Ｐ３潜伏期短于任务Ｐ３；高度选择注意时Ｐ３潜伏期长；再认母亲与再认指定陌生人照片Ｐ３潜伏期无显著差异，是幼儿记忆发育良好的表现。反应时间长于Ｐ３潜伏期可以做为幼儿思维支配行为的佐证。     

幼儿视觉ERP：I．P_3波幅的研究

本研究的目的是了解幼儿在人像再认过程中Ｐ３波幅变化规律，为幼儿认知发育提供神经电生理的依据。结果证明幼儿无任务Ｐ３波幅比任务ｐ３波幅低，Ｐ３的引出与低概率刺激有关。再认熟悉人Ｐ３波幅大于再认陌生人，推论再认熟悉人的场合修正量大于再认陌生人。幼儿Ｐ３波幅的部位效应表现为从Ｏｚ至Ｆｚ渐次降低。Ｐ３波幅变化还与幼儿记忆、注意等心理过程有关。     

正常人的视觉事件相关电位研究

本文利用三种视觉符号编排的刺激序列，记录了９５名正常人的视觉ＥＲＰ，报道了Ｆｚ、Ｐｚ点Ｎ２、Ｐ３波幅和潜伏期的正常值及Ｎ２、Ｐ３的影响因素。结果表明：该刺激序列可引出清晰、稳定的ＥＲＰ波形；Ｐ３波幅与任务和部位有关，靶Ｐ３波幅大于非靶Ｐ３，靶Ｐ３于Ｐｚ点波幅大于Ｆｚ，非靶Ｐ３在Ｆｚ、Ｐｚ点间波幅无明显差异；Ｎ２波幅与任务无关，靶与非靶之间Ｎ２波幅无差异，而与部位有关，Ｆｚ点波幅大于Ｐｚ点；Ｎ２、Ｐ３受年龄的影响．中老年人Ｎ２、Ｐ３潜伏期长于青年人，而波幅中老年人较青年人低。     

老年人视觉、听觉及体感诱发的ERP比较

对３０位神经系统正常、精神活动完整的老年人同时进行视觉、听觉、体感不同刺激模式检测得到的事件相关电位（ＥＲＰ）进行比较分析，结果提示不同的刺激模式诱发出来的ＥＲＰ各波的潜伏期、波幅、波型是不同的。如视觉刺激时Ｐ３波潜伏期为４００．７４±２６．５２ｍｓ，波幅为８．３５±４．９６μｖ；听觉刺激时Ｐ３波潜伏期为３３９．５２±２３．９０ｍｓ，波幅为８．４０±５．４３μｖ；体感刺激时Ｐ３波潜伏期为３４６．２±３５．１ｍｓ，波幅为８．５６±２．１４μｖ。并对不同刺激模式的最佳记录部位和产生机制进行初步讨论。     

正常青年人视觉、听觉诱发的ERP的比较

对３５例正常青年人同时进行视觉、听觉不同刺激模式检测到的事件相关电位（ＥＲＰ）进行比较分析，发现不同刺激模式诱发出的ＥＲＰ各波的潜伏期、波幅均不相同。本文对其原因和不同年龄的Ｐ３波在颅顶有不同的分布部位以及其中一些Ｐ３波电位值两半球不对称性的机理进行了初步探讨。     

智力低下儿童事件相关电位的研究

对３１例智力低下儿童进行事件相关电位（ＥＲＰ）和智商（ＩＱ）对照研究，并与正常儿童进行比较，发现Ｐ３波之潜伏期（ＰＬ）与ＩＱ的高低有显著的相关性，靶刺激时智力低下儿童组Ｐ２、Ｐ３波波幅较正常儿童组低。提示ＥＲＰ测定是评价智力低下儿童认知功能较为灵敏的一种客观指标。     

10例阿尔茨海默型老年痴呆事件相关电位的初步研究

对１０例临床诊断为阿尔茨海默型老年痴呆（ＳＤＡＴ）的患者及１９例正常人进行听觉事件相关电位（ＥＲＰ）检测，同时还观察ＳＤＡＴ患者体外反搏治疗前后ＥＲＰ的变化。发现患者组Ｎ１波潜伏期明显延长，Ｐ３波出现率低仅４％（正常青年组１００％，老年组８０％）。Ｐ３潜伏期显著延长，波幅明显降低。体外反搏治疗后，患者组Ｎ１波潜伏期明显缩短，Ｐ３波出现率升至８０％。     

选择性注意与事件相关电位P300研究

事件相关电位（ＥＲＰｓ）常用来研究语义信息的感知，识别编码等易化过程，受试者给予汉语词汇作业刺激，靶刺激以２０％的概率随机呈现，被视觉感知，结果发现Ｐ３００的波幅及潜伏期较敏感地反映语义信息传递及过程，相比较而言靶刺激上发Ｐ３００有较大波幅，较短潜伏期和半球不对称性。     

短暂性脑缺血发作认知功能与事件相关电位研究

目的：探讨短暂性脑缺血发作（ＴＩＡ）病人事件相关电位（ＥＲＰ）的变化规律及其临床意义。方法：用听觉Ｏｄｄｂａｌ刺激序列ＥＲＰ、认知能力筛选试验（ＣＣＳＥ）和简易智力状态试验（ＭＭＳＥ）检测３２例ＴＩＡ病人和３０例年龄、性别、利手和教育程度相匹配的正常人。结果：病人组ＥＲＰ的Ｎ２和Ｐ３峰潜伏期较对照组显著延长（Ｐ＜０．０１），Ｎ２和Ｐ３波幅两组均无显著性差异，Ｐ３峰潜伏期（Ｐ３ＰＬ）异常率为２５％。病人组ＭＭＳＥ较对照组低（Ｐ＜０．０５），但与Ｐ３ＰＬ未见有相关性（ｒ＝－０．２４４，Ｐ＞０．１）；ＣＣＳＥ与对照组无显著差异，但与Ｐ３ＰＬ呈显著负相关（ｒ＝－０．４７３，Ｐ＜０．０１）。结论：ＴＩＡ病人存在不同程度的认知功能障碍。对认知功能障碍的早期发现，ＥＲＰ检则有临床实用价值     

靶与非靶刺激信息的认知事件相关电位比较

对靶与非靶刺激信息的认知事件相关电位进行比较研究。给予受试者汉语词汇作业刺激，被视觉感知，靶刺激以２０％的概率随机呈现，非靶刺激占８０％。结果发现这两种刺激状态下认知事件相关电位成分的Ｎ１，Ｐ２，Ｎ２无显著差异，而Ｐ３，Ｎ４和ＬＰＣ（ＬａｔｅＰｏｓｉｔｉｖｅＣｏｍｐｏｎｅｎｔ）则其波形变化和地形图特征有明显不同，靶刺激激活整个脑区，各波幅均较大，以Ｐ３波最为显著     

Effects of stop-signal modality on the N2/P3 complex elicited in the stop-signal paradigm

The principal aim of the present study was to clarify how stop-signal modality affected the speed and efficacy of stopping, using ERP components as converging measures of stop processes. Both performance and ERP latency findings suggested faster processing of stop signals in the auditory than visual version of the stop task. The effects of successful versus unsuccessful stopping on the amplitude and topography of N2/P3 components elicited by the stop signals appeared to be largely independent of the modality of the stop signals. Stop signals elicited a fronto-central N2 that was much larger on unsuccessful than successful stop trials in stimulus-locked waveforms. N2 was followed by a P3 component that showed a fronto-central distribution on successful stop trials. P3 elicited on unsuccessful stop trials showed a posterior-parietal focus, but this topography was manifested more clearly in response-locked than stimulus-locked waveforms. A dipole source analyses confirmed these topographical differences of P3, and further showed that the location of the corresponding dipoles remained largely identical across the visual and auditory versions of the stop-signal task. Taken together, the present findings support the suggestion that ERP components in the stop task reflect endogenous aspects of stop-signal processing, such as effective inhibition of responses on successful stop trials and detection of errors on failed inhibition trials.     

Auditory event-related potentials in humans and rats: effects of task manipulation

The purpose of this study was to compare components of the rat and human auditory event-related potential (ERP) as generated in active oddball and passive single-stimulus tasks. The rats were trained to discriminate between target and standard stimuli in an oddball task, whereas the human subjects received instructions. Task effects on various ERP components were found in both species. Interestingly, effects on the P3 component were similar in the species with regard to amplitude: Target stimuli elicited a higher amplitude in the oddball task than did standard stimuli. This might indicate that the P3 shares the same characteristics between species. However, the first four components occurred 1.82 times earlier in rats than in humans, expecting a P3 of about 200 ms in rats. The P3 in rats appeared at 380 ms. We conclude that either the relation between human and rat peak latencies is not linear, or the P3 in rats is not the equivalent of the human P3.     

Electrophysiological correlates of grapheme-phoneme conversion

The cortical processes underlying grapheme-phoneme conversion were investigated by event-related potentials (ERPs). The task consisted of silent reading or vowel-matching of three Japanese hiragana characters, each representing a consonant-vowel syllable. At earlier latencies, typical components of the visual ERP, namely, P1 (110 ms), N1 (170 ms) and P2 (300 ms), were elicited in the temporo-occipital area for both tasks as well as control task (observing the orthographic shapes of three Korean characters). Following these earlier components, two sustained negativities were identified. The earlier sustained negativity, referred here to as SN1, was found in both the silent-reading and vowel-matching task but not in the control task. The scalp distribution of SN1 was over the left occipito-temporal area, with maximum amplitude over O1. The amplitude of SN1 was larger in the vowel-matching task compared to the silent-reading task, consistent with previous reports that ERP amplitude correlates with task difficulty. SN2, the later sustained negativity, was only observed in the vowel-matching task. The scalp distribution of SN2 was over the midsagittal centro-parietal area with maximum amplitude over Cz. Elicitation of SN2 in the vowel-matching task suggested that the vowel-matching task requires a wider range of neural activities exceeding the established conventional area of language processing.     

P300 and slow wave from oddball and single-stimulus visual tasks: inter-stimulus interval effects.

The effects of inter-stimulus intervals on P300 from an oddball task (target and standard stimuli) and a single-stimulus task (targets only) employing simple visual stimuli were assessed in order to determine how a relatively long ISI affects event-related brain potentials (ERPs). Young adult subjects (n=16) responded by pressing a button to a visual target stimulus of each task condition. ISI was either 2.5 or 30 s and paradigm type was either the oddball or single-stimulus task. ERPs were recorded from the midline electrodes, with amplitude, mean area, and latency of the P300 and other components assessed. The results showed that P300 morphology was dramatically affected by task and ISI such that under the 2.5 s condition, the oddball paradigm produced typical ERP components, whereas the single-stimulus condition demonstrated minimal P300 amplitude. When ISI was 30 s, both the oddball and single-stimulus tasks produced robust P300 components but also evinced strong slow wave (SW) potentials, which contributed to the ERP measurement outcomes. It is concluded that P300 from visual stimuli can be elicited with both oddball and single-stimulus tasks when ISI is relatively long. ERPs from both paradigms produced appreciable SW activity, which needs to be considered when long ISI procedures are employed.     

Response mode and P300 from auditory stimuli

The P300 component of the event-related brain potential (ERP) was elicited with a simple auditory discrimination task. Subjects were required to respond in three different ways to target stimuli across conditions: (1) silently counting the targets; (2) tapping their index finger every time a target was detected; or (3) pressing a button with their thumb when a target was presented. In addition, ERPs were recorded during each response mode while the subjects' eyes were either open or closed. P300 amplitude was larger for the counting compared to the tapping or button press tasks especially during the eyes closed condition. The peak latency of the P300 was longer when obtained from the counting compared to the tapping and button-press tasks for both eye conditions. Response mode also interacted with electrode site for peak latency. The results suggest that the P300 ERP component is sensitive to the nature of the subject's response during discrimination tasks.     

P300 habituation from auditory single-stimulus and oddball paradigms.

The habituation of auditory P300 event-related brain potential (ERP) from single-stimulus paradigm was evaluated and compared to that from oddball paradigm. Three task conditions were: oddball with a button press (oddball/press) response, single-stimulus with a button-press (single-stimulus/press) response and a silent count (single-stimulus/count) response. The oddball/press condition demonstrated larger P300 amplitude and longer latency overall than either single-stimulus condition, but P300 amplitude decreased and peak latency increased similarly over successive trial blocks for all three tasks. Thus, the oddball and single-stimulus ERP tasks produce analogous changes under repeated measurements and indicate that the single-stimulus task can serve as an alternative method for eliciting the P300 in applied and clinical settings.     

The effects of covert attention and stimulus complexity on the P3 response during an auditory continuous performance task.

This study examined the effects of motor responding and stimulus complexity on the event-related potential (ERP) P3 amplitude and latency during an auditory continuous performance task (A-CPT). Subjects were presented with undegraded and degraded syllables during two experimental conditions. In the motor attention (MA) condition participants performed a button press to target syllables. In the covert attention (CA) condition, participants listened for target syllables without responding. The ERP P3 amplitude for targets during MA and CA showed the expected anterior-to-posterior scalp topography, with the greatest amplitude at Pz. Although amplitudes across all scalp sites were greater for MA than CA target P3 responses, both MA and CA targets had greater P3 amplitudes than the P3 for the nontarget syllables (NT). There was no effect of stimulus complexity (degraded vs. undegraded) on P3 amplitude. However, stimulus complexity did affect P3 latency. Degraded syllables elicited longer P3 latency than undegraded syllables for both the MA and CA conditions. The amplitude and topography findings show that when stimulus probability is controlled through the use of a CPT paradigm, a reliable P3 component is present even when the task does not require a motor response to target stimuli.     

P300 and handedness: On the possible contribution of corpus callosal size to ERPs

The P300 event-related potential (ERP) was elicited in left- and right-handed young adult male and female participants ( n = 20Ygroup) with both auditory and visual stimulus discrimination tasks that varied systematically in difficulty. P300 amplitude was larger across all task conditions for left- than for right-handed participants at anterior and central electrode sites. P300 latency was shorter across all task conditions for left- than for right-handers. Task difficulty did not affect the ERP handedness differences. Male and female subjects demonstrated comparable ERP handedness effects, although smaller P300 components were obtained for males than for females. When considered in the context of corpus callosal size differences for left- versus right-handed and male versus female participants, the findings suggest that the P300 reflects callosal size and interhemispheric transmission efficacy.     

Categorization of unilaterally presented emotional words: an ERP analysis

This study is intended to clarify the functional role of different ERP components as indicators of the processing of emotions. The effect of emotional connotation of words on hemispheric lateralization is also explored. Visual ERPs were recorded to unilaterally presented positive, negative, and neutral words that should be categorized according to their emotional connotation. The P2 amplitude was larger to positive than to negative words whereas P3 amplitude was larger to positive words compared with neutral ones. The slow positive wave (SPW) was influenced by words emotionality at anterior and posterior sites differently. The amplitude of the N1 component was larger in the left hemisphere to contralaterally presented words. The P2 and P3 components were larger over the left hemisphere whereas the N3 and N4 components were larger over the right hemisphere to ipsilateral stimulation. The results support our hypotheses on the functional role of positive ERP components in the processing of an affective words connotation: the P2 wave reflects a general evaluation of emotional significance, the P3 a task-related decision, and the SPW an additional decision control in the context of the emotional experience of an individual. Neither the "right hemisphere hypothesis" nor "valence hypothesis" on lateralization of the processing of emotions were confirmed. Each hemisphere seems to exert its effect on emotion through specific hemispheric resources that are unequally allocated along the different stages of task processing and may cause alternation of hemispheric dominance.