CHARACTERIZATION OF P3 AN DCVN SOURCES USING MEG, EEG, &

P300或P3是感觉诱发电位的晚期阳性成分， 据说反映了各种认知功能，并提供了一个 正常人和神经学上的信息加工客观指数 妥协的人。 认知神经科学中的一个重要问题是 是识别产生它的大脑结构。然而， 为此目的进行了广泛的调查， 颅内记录和绘制其头皮分布已经被 不确定 使用脑磁图（MEG），一种类似于传统方法的方法， 电生理学，但更大的空间分辨率，我们已经记录了 磁等效P3听觉刺激，并已定位其 颞叶的上级表面上的信号源。 我们还发现 证据表明，更深的来源（可能是丘脑）可能有助于其 发病 这些结果导致两个一般假设：（a）P3是 模态特异性和（B）模态特异性皮层激活 早期的丘脑活动先于这些区域。 我们建议在一系列的十二个测试这些一般假设 实验中，P3的罕见和意外失踪的听觉，视觉 并且在两种条件下获得体感刺激。 人会 涉及对刺激的注意力，导致长潜伏期P3， 被认为主要反映了高阶认知操作。 另 将涉及忽略刺激，导致较短的潜伏期P3 与更基本的感官功能有关。 P3的来源估计 不同的刺激方式和条件下获得的，预计 将被用于回答以下问题： P3是否是特定的模式，它们是否共享早期丘脑 起源和不同的结构是否产生P3的存在或 没有参加或偶然登记的意外环境 事件

The P300 or P3, a late positive component of sensory evoked potentials, is said to reflect a variety of cognitive functions and to provide an objective index of information processing in normal and neurologically compromised individuals. An important issue in cognitive neuroscience has been the identification of the brain structures that generate it. However, extensive investigations conducted for that purpose and involving intracranial recordings and mapping of its scalp distribution have been inconclusive. Using magnetoencephalography (MEG) a method akin to traditional electrophysiology, but of greater spatial resolution we have recorded the magnetic equivalent of P3 to auditory stimuli and have localized its sources on the superior surface of the temporal lobe. We also found evidence that deeper sources (possibly thalamic) may contribute to its onset. These results lead to two general hypotheses: (a) That P3s are modality-specific and (b) that activation of modality-specific cortical regions is preceded by early thalamic activity. We propose to test these general hypotheses in a series of twelve experiments where P3s to rare and to unexpectedly missing auditory, visual and somatosensory stimuli will be obtained under two conditions. One will involve attention to stimuli resulting in a long latency P3, which is thought to reflect mostly higher order cognitive operations. The other will involve ignoring the stimuli, resulting in a shorter latency P3 associated with more basic sensory functions. The estimated sources of P3s obtained with the different stimulus modalities and conditions, projected onto individual magnetic resonance images (MRIs) will be used to answer whether P3s are modality-specific, whether they share an early thalamic origin and whether different structures generate P3s to the presence or absence of attended or incidentally registered unexpected environmental events.