ERPS AND VERBAL MEMORY IN AGING DEMENTIA AND AMNESIA

具体目的：拟议的与药物相关的潜在实验目的 来描述记忆障碍的电生理学相关性 健忘症、痴呆症和衰老。我们将使用事件相关电位 (ERP)研究语言和文字记忆过程的技术 沿着这些过程的行为测量。特定的大脑 感兴趣的电位是N4 OO，这是一种晚期负ERP，峰值在 刺激后约400毫秒，晚期阳性成分 (LPC)接下来是N400电位已被证明是衡量 语义处理的幅度有一个强逆 相关性与引出词出现在 考虑到上下文。LPC，类似于P300或“P3 b”，与 任务难度和记忆过程。 我们设计了一个ERP字 利用听觉语境/视觉目标词的复述范式 在语义分类任务中配对， 不同的时间间隔。这一范例显示了提供 内隐和外显言语的电生理测量 记忆过程 我们对健忘症患者的初步研究表明 N400对新目标词和重复目标词的差异 (i.e.“N400重复效应"与正常情况下所见的相同 对照相反，健忘症患者的LPC异常降低， 重复效应和这种减少的程度与 外显记忆受损。待检验的具体假设为： 1)痴呆患者的单词重复效果会降低， LPC，但不是在N400上，反映了显式的损害，而不是 内隐的记忆过程 2)一个减少LPC重复效应将是一个敏感的迹象记忆 可能有助于区分非痴呆症患者的年龄- 相关记忆障碍（AAMI）。 3)难治性抑郁症患者的LPC会降低 电休克过程中失忆时的重复效应 治疗（ECT），但不是在ECT之前或之后。 4)在被诊断为阿尔茨海默病“高危”的患者中， N400电位异常或LPC重复效应者， 比ERP正常的人更容易患痴呆症。 5)N400电位和LPC重复效应将在 阿尔茨海默病、多发性梗死性痴呆和正常受试者 老年人对照。 研究设计：事件相关电位的病例对照和纵向研究 与相关行为数据进行比较。 方法：记录正常人和记忆障碍者的事件相关电位 在语义分类任务中。重复和一致性（程度 与一个类别相适应）将系统地变化，以引起 并调节N400和LPC脑电位。N400和LPC的比较 将在受试者组之间和受试者组内确定特征， 与外显记忆能力和其他神经心理学数据有关。

Specific Aims: The proposed Language-Related Potential experiments aim to characterize the electrophysiological correlates of memory impairment in amnesia, dementia and aging. We will use the Event-Related Potential (ERP) technique to investigate language and verbal memory processes along with behavioral measures of these processes. The specific brain potentials of interest are the N4OO, a late negative ERP which peaks at approximately 400 msec post-stimulus, and the late positive component (LPC) which follows. The N400 potential has been shown to be a measure of semantic processing with its amplitude having a strong inverse correlation with the probability of the eliciting word appearing in a given context. The LPC, akin to the P300 or "P3b", has been related to both task difficulty and memory processes. We have designed an ERP word repetition paradigm which utilizes auditory context/visual target word pairs in a semantic categorization task and repeats these pairs at varying time intervals. This paradigm shows promise in providing electrophysiological measures of both implicit and explicit verbal memory processes. Our preliminary studies of amnesic patients suggest that the difference in the N400 to new versus repeated target words (i.e. the "N400 repetition effect~) is equivalent to that seen in normal controls. In contrast, the amnesics show an abnormal reduced LPC repetition effect and the degree of this reduction correlates well with impairment of explicit memory. Specific hypotheses to be tested are: 1) Amnesic patients will have a reduced effect of word repetition upon the LPC, but not upon the N400, reflecting impairment of explicit, not implicit, memory processes. 2) A reduced LPC repetition effect will be a sensitive sign of memory impairment and may help distinguish non-demented individuals with age- associated memory impairment (AAMI) from normal elderly. 3) Patients with refractory depression will have a reduced LPC repetition effect when amnesic during the course of electroconvulsive therapy (ECT) but not prior to nor following ECT. 4) Among patients diagnosed as being "at risk" for Alzheimer's disease, those with abnormal N400 potentials or LPC repetition effects will be more likely to develop dementia than those with normal ERPs. 5) The N400 potential and LPC repetition effects will differ between subjects with Alzheimer's disease, multi-infarct dementia and normal elderly controls. Research design: Case-control and longitudinal studies of ERPs with comparisons to relevant behavioral data. Methods: ERPs will be recorded from normal and memory-impaired subjects during a semantic categorization task. Repetition and congruity (degree of fit with a category) will be varied systematically in order to elicit and modulate N400 and LPC brain potentials. Comparisons of N400 and LPC characteristics will be made between and within subject groups and related to explicit memory abilities and other neuropsychological data.