Sumiyoshi Chika, Narita Zui, Inagawa Takuma, Yamada Yuji, Sueyoshi Kazuki, Hasegawa Yumi, Shirama Aya, Hashimoto Ryota, Sumiyoshi Tomiki
Faculty of Human Development and Culture, Fukushima University, Fukushima, Japan.
Department of Preventive Intervention for Psychiatric Disorders, National Center of Neurology and Psychiatry, Kodaira, Japan.
Front Neurol. 2021 Feb 11;12:583027. doi: 10.3389/fneur.2021.583027. eCollection 2021.
Beneficial effects of transcranial direct current stimulation (tDCS) are relevant to cognition and functional capacity, in addition to psychiatric symptoms in patients with schizophrenia. However, whether tDCS would improve higher-order cognition, e.g., semantic memory organization, has remained unclear. Recently, text-mining analyses have been shown to reveal semantic memory. The purpose of the current study was to determine whether tDCS would improve semantic memory, as evaluated by text-mining analyses of category fluency data, in patients with schizophrenia. Twenty-eight patients entered the study. Cognitive assessment including the category fluency task was conducted at baseline (before tDCS treatment) and 1 month after t administration of tDCS (2 mA × 20 min, twice per day) for 5 days, according to our previous study. The category fluency data were also obtained from 335 healthy control subjects. The verbal outputs (i.e., animal names) from the category fluency task were submitted to singular valued decomposition (SVD) analysis. Semantic memory structures were estimated by calculating inter-item cosines (i.e., similarities) among animal names frequently produced in the category fluency task. Data were analyzed longitudinally and cross-sectionally to compare the semantic structure within the patient group (i.e., baseline vs. follow-up) and between groups (patients vs. healthy controls). In the former, semantic associations for frequent items were compared in the form of cosine profiles, while in the latter, the difference in the magnitude of the correlations for inter-item cosines between healthy controls and patients (baseline, follow-up) was examined. Cosine profiles in the patient group became more cluster-based (i.e., pet, carnivores, and herbivores) at follow-up compared to those at baseline, yielding higher cosines within subcategories. The correlational coefficient of inter-item cosines between healthy controls and patients was significantly greater at follow-up compared to baseline; semantic associations in patients approached the normality status after multi-session tDCS. To our knowledge, this is the first study to demonstrate the facilitative effect of tDCS on semantic memory organization in patients with schizophrenia. Text-mining analysis was indicated to effectively evaluate semantic memory structures in patients with psychiatric disorders.
经颅直流电刺激（tDCS）的有益效果不仅与精神分裂症患者的精神症状有关，还与认知和功能能力相关。然而，tDCS是否能改善高阶认知，例如语义记忆组织，仍不清楚。最近，文本挖掘分析已被证明可揭示语义记忆。本研究的目的是确定tDCS是否能改善精神分裂症患者的语义记忆，这通过对类别流畅性数据的文本挖掘分析来评估。28名患者进入该研究。根据我们之前的研究，在基线（tDCS治疗前）以及tDCS治疗（2毫安×20分钟，每天两次）5天后的1个月进行包括类别流畅性任务在内的认知评估。类别流畅性数据也从335名健康对照者中获取。将类别流畅性任务中的言语输出（即动物名称）进行奇异值分解（SVD）分析。通过计算类别流畅性任务中频繁产生的动物名称之间的项目间余弦值（即相似度）来估计语义记忆结构。对数据进行纵向和横向分析，以比较患者组内（即基线与随访）以及组间（患者与健康对照）的语义结构。在前一种情况中，以余弦曲线的形式比较频繁项目的语义关联，而在后一种情况中，检查健康对照者与患者（基线、随访）之间项目间余弦值相关性大小的差异。与基线相比，患者组在随访时的余弦曲线在基于聚类方面（即宠物、食肉动物和食草动物）变得更明显，在子类别内产生更高的余弦值。与基线相比，健康对照者与患者之间项目间余弦值的相关系数在随访时显著更大；多疗程tDCS后患者的语义关联接近正常状态。据我们所知，这是第一项证明tDCS对精神分裂症患者语义记忆组织具有促进作用的研究。文本挖掘分析被证明可有效评估精神疾病患者的语义记忆结构。
