Fein G, Turetsky B
University of California, San Francisco.
Electroencephalogr Clin Neurophysiol. 1989 May;72(5):384-94. doi: 10.1016/0013-4694(89)90044-8.
The discrepancy in the literature concerning the sensitivity of delayed P300 latency in dementia revolves around the variability of P300 latency in normal elderly. Previous studies, which have produced conflicting results, have utilized different P300 paradigms and different methods for measuring P300 latency. We demonstrate that the reported differences in the variability of P300 latency in normal elderly are likely to have resulted from these differences in paradigm and measurement method. We gathered auditory P300 data from a sample of 50 normal elderly using both a 3-tone RT paradigm and a 2-tone oddball paradigm and measured P300 latency using both peak-picking on the average EP and a single-trial template-fitting procedure. P300 latency variability was increased for the 3-tone paradigm compared to the auditory oddball paradigm, and for the template-fitting method. compared to peak-picking. The increased P300 latency variability when the template-fitting method was employed resulted, in part, from the template-fitting procedure focussing on random noise when the signal-to-noise ratio was low. Increased variability of P300 latency in the 3-tone paradigm resulted from 13 subjects who had a very long-latency positive component (often in addition to an earlier, smaller component) in this paradigm that met the scoring criteria for P300, but that was not seen in the oddball paradigm. We speculate that for the 3-tone task, some subjects may adopt a strategy involving 2 stages of stimulus processing, which results in the generation of 2 positive components, obscuring group differences in P300 latency. These results raise questions concerning the use, in clinical studies designed to yield diagnostic measures, of complicated paradigms in which subjects might adopt varying processing strategies.
文献中关于痴呆症患者延迟P300潜伏期敏感性的差异，主要围绕正常老年人P300潜伏期的变异性。此前的研究结果相互矛盾，这些研究采用了不同的P300范式和测量P300潜伏期的不同方法。我们证明，正常老年人P300潜伏期变异性的差异报道，可能是由于范式和测量方法的这些差异所致。我们使用三音反应时范式和双音oddball范式，从50名正常老年人样本中收集听觉P300数据，并使用平均诱发电位的峰值检测和单试次模板拟合程序测量P300潜伏期。与听觉oddball范式相比，三音范式的P300潜伏期变异性增加；与峰值检测相比，模板拟合方法的P300潜伏期变异性增加。采用模板拟合方法时P300潜伏期变异性增加，部分原因是在信噪比低时，模板拟合程序关注的是随机噪声。三音范式中P300潜伏期变异性增加，是因为有13名受试者在该范式中有一个潜伏期很长的正向成分（通常除了一个较早出现的较小成分），符合P300评分标准，但在oddball范式中未出现。我们推测，对于三音任务，一些受试者可能采用涉及两个刺激处理阶段的策略，这导致产生两个正向成分，掩盖了P300潜伏期的组间差异。这些结果引发了关于在旨在产生诊断指标的临床研究中，使用受试者可能采用不同处理策略的复杂范式的问题。
