Abstract:

Sustained attention refers to the ability to maintain attention on particular stimuli or cognitive tasks over time. However, attention levels fluctuate over time, which can impede ongoing cognitive processes. Even an ephemeral lapse in attention can lead to numerous negative effects，such as dropped academic performance, work-related errors, and even safety hazards. The typical development of sustained attention, along with its abnormal fluctuations in patients with neurological and psychiatric disorders, occur across multiple infra-slow frequencies. Several theoretical models, including resource-depletion theory, mindlessness theory, and resource-control theory, have been proposed to explain the mechanism of fluctuations in sustained attention. However, current research within these models oversimplifies the fluctuations as a mere trade-off and allocation of limited cognitive resources, thereby impeding the analysis of the complex array of cognitive components and diverse characteristics of multiple frequency fluctuations in sustained attention.

This study aims to elucidate the cognitive and neural mechanisms underlying low-frequency fluctuations in sustained attention, by combining multi-modal techniques and noninvasive brain stimulation methods such as behavioral experiments, electroencephalogram (EEG), and functional magnetic resonance imaging (fMRI). The research comprises three specific studies.

In Study 1, we utilized the classic gradual-onset continuous performance task (GradCPT) to integrate behavioral, physiological, and neural fluctuation characteristics in order to distinguish between different cognitive components involved in sustained attention. Our hypotheses regarding cognitive component fluctuations were formulated based on an examination of the brain's spatiotemporal characteristics linked to different cognitive component fluctuations.

Based on the conclusions of Study 1, Study 2 delved into interventions based on low-frequency fluctuations of sustained attention components. This was achieved through the application of infra-slow wave transcranial electrical stimulation (TES) to corroborate the proposed hypotheses concerning frequency, timing, and targeted brain regions. The convergence of Study 1 and Study 2 may offer causal evidence supporting the notion that "different cognitive components exhibit distinct fluctuation characteristics. Together, these studies have collaboratively established and refined the proposed hypotheses.

Study 3 investigated the interaction between sustained attention and attentional networks by using the High Reliability-Composite Attention Test (HR-CAT) to explore differences in sustained attention fluctuations across alerting, orienting, executive control and baseline conditions. This research aimed to extend the proposed hypotheses and improve the ecological validity and practical significance of the study.

This study highlights several significant innovations. First of all, the study expanded the theory of attention and filled the gap in the current theory by elucidating how different components of sustained attention contribute to its slow fluctuating process. Through systematic separation of core components of sustained attention and analysis of their internal structure, we explored fluctuation characteristics driven by different cognitive components, leading to the development of the theory of sustained attentional fluctuations.

Secondly, this study shed insight into the theory of brain function by establishing connections between specific cognitive components and the spatiotemporal structure of brain function. It established a coherent pathway from neural oscillation to cognitive fluctuation to overall fluctuation in sustained attention, unveiling the cognitive neural mechanism behind sustained attention fluctuation. By exploiting behavioral, EEG, and fMRI techniques as well as infra-slow wave TES and global spatiotemporal topology analysis, this study explored the cognitive neural mechanisms of sustained attention fluctuations from the perspective of physiological-psychological-neural coupling. In terms of methods, the study advanced research on the spatiotemporal structure of brain regions and brain networks involved in cognitive function, and contributed to the refinement of current theories of brain function. In terms of content, the study focused on infra-slow brain activity instead of traditional neural rhythms, which promotes a better understanding of the “macro fluctuation” and “slow process” of psychological activity.

Lastly, the study enriches the field of non-invasive brain intervention by indentifying precise spatiotemporal targets for sustained attentional fluctuations. Infra-slow wave TES leverage these fluctuation characteristics to enhance sustained attention, while minimizing potential harm from fluctuations.

To sum up, this study advances our understanding of the cognitive and spatiotemporal aspects of sustained attention, offering insights that can inform precise interventions for managing fluctuations in sustained attention. It offers novel insights into sustained attention mechanisms and brain function theories, laying the theoretical groundwork for non-invasive brain intervention strategies and mitigating attention fluctuations in clinical applications.

Key words: sustained attention, brain-spatiotemporal characteristics, low-frequency brain activity, infra-slow wave transcranial electrical stimulation, attentional network