Wang Jiunn-Kae, Sahu Prangya Parimita, Ku Hsiao-Lun, Lo Yu-Hui, Chen Ying-Ru, Lin Che-Yin, Tseng Philip
Department of Psychiatry, Shuang Ho Hospital, Taipei Medical University, New Taipei City, Taiwan.
Department of Psychiatry, School of Medicine, College of Medicine, Taipei Medical University, Taipei, Taiwan.
Schizophrenia (Heidelb). 2024 Oct 26;10(1):97. doi: 10.1038/s41537-024-00518-5.
Schizophrenia is a complex neuro-psychiatric disorder including positive symptoms, negative symptoms, and cognitive deficits. A key cognitive dysfunction in schizophrenia is a deficit in visual working memory (VWM). VWM involves three distinct stages: encoding, maintenance, and retrieval. The deficit in any one stage would produce the same symptom (i.e., poor VWM), although their causes are not the same. In this study, we used a retro-cue VWM task that provides helpful cues at different stages: early in maintenance (early cue), late in maintenance (late cue), or during retrieval (retrieval cue). This modification would help "tag" or identify the cognitive stage(s) most responsible for impaired VWM performance in schizophrenia. Additionally, we took advantage of this tagging feature and applied 6 Hz transcranial alternating current stimulation (tACS) over the right dorsolateral prefrontal cortex (DLPFC) and right posterior parietal cortex (PPC)-which has previously been shown to enhance VWM in low-performing healthy individuals-to examine whether tACS would improve a specific stage or all stages of VWM processing in schizophrenia. We observed that cues significantly enhanced performance in low-performing patients, who benefited equally from early and late maintenance cues, but not from retrieval cues. These low-performers also responded well to theta tACS in their overall VWM performance as opposed to a specific VWM stage. No improvement effect was observed in high-performing patients for both retro cue and tACS. Together, our data suggest that 1) low-performing patients' VWM deficits likely stem from poor memory consolidation rather than retrieval, 2) right frontoparietal theta tACS can improve low-performing patients' VWM performance, and 3) such facilitatory tACS effect is not selective of a specific VWM stage and thus is likely driven by an improvement in overall visual attention.
精神分裂症是一种复杂的神经精神障碍，包括阳性症状、阴性症状和认知缺陷。精神分裂症的一个关键认知功能障碍是视觉工作记忆（VWM）缺陷。VWM涉及三个不同阶段：编码、维持和提取。任何一个阶段的缺陷都会产生相同的症状（即VWM不佳），尽管其原因不尽相同。在本研究中，我们使用了一种逆向线索VWM任务，该任务在不同阶段提供有用线索：维持早期（早期线索）、维持晚期（晚期线索）或提取期间（提取线索）。这种修改将有助于“标记”或识别对精神分裂症中VWM表现受损最负责的认知阶段。此外，我们利用这种标记功能，在右侧背外侧前额叶皮层（DLPFC）和右侧顶叶后皮层（PPC）施加6赫兹经颅交流电刺激（tACS）——此前已证明该刺激可增强低表现健康个体的VWM——以检查tACS是否能改善精神分裂症患者VWM处理的特定阶段或所有阶段。我们观察到，线索显著提高了低表现患者的表现，这些患者从早期和晚期维持线索中获得的益处相同，但从提取线索中未受益。与特定的VWM阶段相比，这些低表现者在其整体VWM表现中对theta tACS也有良好反应。对于逆向线索和tACS，高表现患者均未观察到改善效果。总之，我们的数据表明：1）低表现患者的VWM缺陷可能源于记忆巩固不佳而非提取；2）右侧额顶叶theta tACS可改善低表现患者的VWM表现；3）这种促进性tACS效应并非特定于VWM的某个阶段，因此可能是由整体视觉注意力的改善所驱动。
