A frequent finding when studying substrates of working memory (WM) deficits in people with schizophrenia (PSZ) is task-induced hyperactivation relative to healthy control subjects (HCS) when WM load is low. Hyperactivation accompanying similar performance is commonly attributed to cognitive deficits rendering relatively easy operations more resource-consuming. To test if hyperactivation at low load really is secondary to cognitive impairment in PSZ, we re-analyzed functional MRI data showing left posterior parietal cortex (PPC) hyperactivation in PSZ when holding a single color-item in WM. In subgroups matched for the number of items successfully stored in WM (K) by excluding the highest-performing HCS and lowest-performing PSZ, performance was almost identical across all set sizes (1-7). While BOLD activation at the larger set sizes did not differ between groups, PSZ still robustly hyperactivated left PPC when a single item had to be maintained. The same pattern was observed in subgroups matched for model-based estimates of WM capacity or attentional lapse rate. Given that in the K-matched subsamples PSZ performed as well as HCS even in the most challenging load conditions and that no BOLD signal difference was seen at high loads, it is implausible that PSZ over-recruited WM-related neural structures because they were more challenged by maintaining a single item in WM. Instead, the findings are consistent with a primary schizophrenia-related processing abnormality as proposed by the hyperfocusing hypothesis, which suggests that an abnormally narrow but intense focusing of processing resources is central to many aspects of impaired cognition in PSZ.

中文翻译：

---

低工作记忆负荷下的皮质过度活化：精神分裂症患者的主要加工异常吗？

研究精神分裂症（PSZ）患者的工作记忆（WM）缺陷的底物时，一个常见发现是相对于健康对照对象（HCS）的任务诱发的过度激活。伴随类似表现的过度激活通常归因于认知缺陷，这使得相对容易的操作更加消耗资源。为了测试低负荷下的过度激活是否真的是PSZ认知障碍的继发因素，我们重新分析了功能性MRI数据，显示了在WM中保持单个颜色项时PSZ的左后顶叶皮层（PPC）过度激活。通过排除性能最高的HCS和性能最低的PSZ，在与成功存储在WM（K）中的项目数量匹配的子组中，所有设置大小（1-7）的性能几乎相同。尽管两组之间在较大尺寸下的BOLD激活没有差异，但是当必须维护单个项目时，PSZ仍会强烈激活左PPC。在基于模型的WM能力或注意失效率估计值匹配的亚组中观察到了相同的模式。假设即使在最具挑战性的负载条件下，在K匹配的子样本中PSZ的表现也与HCS一样，并且在高负载下也看不到BOLD信号的差异，所以PSZ过度招募WM相关的神经结构是不可信的，因为它们更加通过维护仓库管理中的单个项目来挑战。相反，这些发现与超聚焦假说所提出的原发性精神分裂症相关的处理异常一致，