ERPS AND VERBAL MEMORY IN AGING DEMENTIA AND AMNESIA

具体目标：拟议的语言相关电位实验目标 描述记忆损害的电生理学相关性 在健忘症、痴呆症和衰老中。我们将使用与事件相关的电位 研究语言和言语记忆过程的(ERP)技术 以及这些过程的行为测量。特定的大脑 令人感兴趣的潜力是N4OO，这是一种晚期的负ERP，其峰值为 刺激后约400毫秒，以及后期正向分量 (LPC)。N400的潜力已被证明是一种衡量标准 其幅度具有很强的反转的语义加工 与诱导词出现在 在给定的背景下。LPC，类似于P300或“P3b”，一直与 任务难度和记忆过程。我们已经设计了一个ERP Word 利用听觉语境/视觉目标词的重复范式 ，并在语义分类任务中重复这些对 不同的时间间隔。这一范例在提供 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对新单词和重复目标单词的差异 (即“N400重复效应~”)相当于正常情况下的 控制。相反，赦免试验显示LPC异常降低。 重复效应和这种减少的程度与 外显记忆受损。需要检验的具体假设是： 1)健忘症患者单词重复的影响会降低 LPC，但不在N400上，反映显式的减损，而不是 内隐的，记忆过程。 2)LPC重复效应减弱将是记忆的敏感信号 损害，并可能有助于区分年龄的非痴呆者- 正常老年人的相关记忆障碍(AAMI)。 3)顽固性抑郁症患者的LPC会降低 电惊厥过程中健忘时的重复效应 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“风险”的患者中， 具有异常N400电位或LPC重复效应的患者将 比那些ERPs正常的人更容易患上痴呆症。 5)N400电势和LPC重复效应在 阿尔茨海默病、多梗死性痴呆和正常受试者 老年对照组。 研究设计：ERPS的病例对照和纵向研究 与相关行为数据进行比较。 方法：记录正常人和记忆受损受试者的事件相关电位 在语义分类任务期间。重复性和一致性(度 符合某一类别的)将被系统地改变，以便引起 并调节N400和LPC脑电势。N400与LPC的比较 将在主题组之间和内部制定特征，并 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.