Effects of sleep quality on the offline storage state of visual working memory

Visual working memory (VWM) is a core cognitive function in humans, which enables flexible and efficient storage of visual information from complex contexts into either online or offline states in accordance with current task demands. Among these two states, the offline state demonstrates greater advantages in resisting interference and stabilizing stored information. Previous research has demonstrated that an individual's sleep quality can predict performance in VWM tasks. However, these studies have primarily focused on the online storage state of VWM. To date, there remains unclear whether sleep quality affects the offline storage state, and whether its influence differs between the two distinct storage states. This study aimed to clarify the behavioral association between sleep quality and VWM online and offline storage performance.

The present study employed a mixed experimental design, combining the Pittsburgh Sleep Quality Index with a sequential presentation retrieval paradigm to examine the effects of sleep quality on different storage states of VWM. Valid data were obtained from 76 volunteers (mean age = 19.95 ± 1.72 years, male proportion = 27.63%). All participants completed the standard Pittsburgh Sleep Quality Index assessment to obtain comprehensive subjective sleep quality scores, which were adopted as the core predictive indicator for subsequent behavioral correlation analysis.

The experimental results showed that the total score of participants' sleep quality was significantly negatively correlated with VWM accuracy in both online and offline states. In addition, for VWM accuracy, the main effects of sleep quality and VWM storage state were significant, and a significant interaction effect between sleep quality and storage state was also observed. Simple effect analyses further revealed that participants with higher sleep quality exhibited significantly higher VWM accuracy in the offline state compared with those with lower sleep quality. For VWM reaction time, only a significant main effect of VWM storage state was identified.

These behavioral findings indicate that sleep quality exerts differential influences on distinct VWM storage states. Specifically, poor sleep quality imposes a more pronounced detrimental effect on VWM offline accuracy relative to the online state. This study provides empirical behavioral evidence supporting the differentiation between online and offline VWM storage states and supplements existing research on the association between sleep quality and VWM performance.