Electrophysiological Evaluation of Cognitive Functions (Perception, Language, and Memory) in Schizophrenia

为了研究精神分裂症在感知、思维（语言）和记忆等认知功能领域的病理生理，我们设计了一个新的实验范式，使用视觉事件相关脑电位（ERP）。该范式包括两个语义分类任务：(1)单词任务（WT）考察单词的语义加工；(2)重复任务（RT）考察单词的记忆加工。在第一项研究中，记录了20名正常志愿者WT和RT的erp。每个任务的NA电位通过减法程序从erp中提取，该方法最初由Ritter等人于1982年报道。WT的NA包括两个负的主峰，尽管第二个NA峰不存在于不可发音的字母中。这表明，第一个和第二个NA峰分别代表了模式识别和模式识别后的额外处理。由于第二次电位在刺激后400 msec左右达到峰值，且不存在不可发音的字母，因此它对应于N400电位，反映了单词的语义加工。在RT中，单词重复降低了N400作为第二个NA峰的振幅。因此，我们的实验范式使我们能够评估模式识别，语义处理和语义记忆。在第二项研究中，我们比较了10名精神分裂症缓解患者和20名匹配的正常对照的WT和RT的原始ERP波形。精神分裂症患者在第一和第二记忆峰上表现迟缓，在第二记忆峰上缺乏单词重复效应。这些异常表明精神分裂症患者在模式识别和语义处理方面的处理速度减慢，也表明精神分裂症患者在利用语义记忆方面存在障碍。我们认为这些异常可能是精神分裂症易感性的核心缺陷，它决定了精神病症状的发生。

In order to examine the pathophysiology of schizophrenia observed in the domains of cognitive functions such as perception, thinking (language), and memory, we devised a new experimental paradigm using a visual event-related brain potential (ERP). The paradigm consisted of two semantic categorization tasks : (1) word task (WT) to examine semantic processing of word and (2) repetition task (RT) to examine memory processing of word.In the first study, ERPs for WT and RT were recorded from 20 normal volunteers. NA potentials for each task were extracted from ERPs by a subtraction procedure originally reported by Ritter et al.in 1982. NA for WT comprised two negative major peaks, although the second NA peak was absent for the unpronounceable letters. These suggest that the first and second NA peaks represent a pattern recognition and an additional processing after pattern recognition, respectively. Since the second peaked at around 400 msec after stimuli and was absent of unpronounceable letters, it corresponds to N400 potential, which reflects semantic processing of word. In the RT,amplitude of N400 as the second NA peak was reduced by word repetition. Therefore, our experimental paradigm enables us to evaluate a pattern recognition, semantic processing, and semantic memory.In the second study, original ERP waveforms of WT and RT were compared between 10 remitted patients with schizophrenia and 20 matched normal controls. The schizophrenic patients showed a retardation of the first and second NA peaks, and a lack of word-repetition effect on the second NA peak. These abnormalities indicate a slowed processing in pattern recognition and semantic processing, and also a disturbance of utilizing semantic memory in schizophrenia. We believe that these abnormalities would be core deficits of schizophrenic vulnerability, which determines occurrence of psychotic symptoms.