CHARACTERIZATION OF THE P3 SOURCE USING MEG EEG AND MRI

P300或P3，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 正常和神经科信息加工的客观指标 受威胁的人。认知神经科学中的一个重要问题是 是对产生它的大脑结构的识别。然而， 为此目的进行了广泛的调查，涉及 颅内的记录和头皮分布的映射已经被 没有定论。 使用脑磁图(MEG)，一种类似于传统方法的方法 电生理学，但更高的空间分辨率，我们记录了 P3对听觉刺激的磁性等价物，并将其定位 位于颞叶上表面的血源。我们还发现 有证据表明更深层次的来源(可能是丘脑)可能有助于其 开始了。这些结果导致了两个普遍的假设：(A)P3是 以及(B)激活特定于模式皮质 区域在丘脑早期活动之前。 我们建议用十二个系列来检验这些一般性假设。 实验中，P3变得罕见，并且意外地丢失了听觉、视觉 并在两种情况下获得体感刺激。一个人会的 涉及对导致长潜伏期P3的刺激的注意，这是 被认为主要反映更高层次的认知操作。另一个 将涉及忽略刺激，从而导致较短的潜伏期P3 与更基本的感觉功能相关。P3的估计来源 在不同的刺激模式和条件下获得，投影 个人磁共振成像(MRI)将用于回答 P3是否具有特定的形态特征，它们是否共享早期丘脑 起源以及不同的结构是否产生P3到存在或 没有出席或附带登记的意外环境 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.