Maryland Psychiatric Research Center, University of Maryland School of Medicine, P.O. Box 21247, Baltimore, MD 21228, USA.
Schizophr Bull. 2011 Sep;37(5):950-7. doi: 10.1093/schbul/sbp164. Epub 2010 Jan 6.
Working memory impairment is considered a core deficit in schizophrenia, but the precise nature of this deficit has not been determined. Multiple lines of evidence implicate deficits at the encoding stage. During encoding, information is held in a precategorical sensory store termed iconic memory, a literal image of the stimulus with high capacity but rapid decay. Pathologically increased iconic decay could reduce the number of items that can be transferred into working memory before the information is lost and could thus contribute to the working memory deficit seen in the illness. The current study used a partial report procedure to test the hypothesis that patients with schizophrenia (n = 37) display faster iconic memory decay than matched healthy control participants (n = 28). Six letters, arranged in a circle, were presented for 50 ms. Following a variable delay of 0-1000 ms, a central arrow cue indicated the item to be reported. In both patients and control subjects, recall accuracy decreased with increasing cue delay, reflecting decay of the iconic representation of the stimulus array. Patients displayed impaired memory performance across all cue delays, consistent with an impairment in working memory, but the rate of iconic memory decay did not differ between patients and controls. This provides clear evidence against faster loss of iconic memory representations in schizophrenia, ruling out iconic decay as an underlying source of the working memory impairment in this population. Thus, iconic decay rate can be added to a growing list of unimpaired cognitive building blocks in schizophrenia.
工作记忆损伤被认为是精神分裂症的核心缺陷，但这种缺陷的确切性质尚未确定。有多种证据表明编码阶段存在缺陷。在编码过程中，信息被存储在一个称为图像记忆的前类别感觉存储中，这是刺激的文字图像，具有高容量但快速衰减。病理性增加的图像记忆衰减可能会减少在信息丢失之前可以转移到工作记忆中的项目数量，从而导致疾病中观察到的工作记忆缺陷。本研究使用部分报告程序来检验以下假设：精神分裂症患者（n=37）比匹配的健康对照组参与者（n=28）表现出更快的图像记忆衰减。六个字母以圆形排列，呈现 50 毫秒。在 0-1000 毫秒的可变延迟后，中央箭头提示要报告的项目。在患者和对照组中，随着提示延迟的增加，回忆准确性下降，反映了刺激数组的图像表示的衰减。患者在所有提示延迟下都表现出记忆受损，这与工作记忆受损一致，但患者和对照组之间的图像记忆衰减率没有差异。这明确排除了精神分裂症中图像记忆表示更快丢失的可能性，排除了图像记忆衰减作为该人群工作记忆损伤的潜在来源。因此，图像记忆衰减率可以添加到精神分裂症中越来越多的未受损认知构建块列表中。
