Abstract
Behavioral experiments evidence that attention is not maintained at a constant level, but fluctuates with time. Recent studies associate such fluctuations with dynamics of attention-related cortical networks, however the exact mechanism remains unclear. To address this issue, we consider functional neuronal interactions during the accomplishment of a reaction time (RT) task which requires sustained attention. The participants are subjected to a binary classification of a large number of presented ambiguous visual stimuli with different degrees of ambiguity. Generally, high ambiguity causes high RT and vice versa. However, we demonstrate that RT fluctuates even when the stimulus ambiguity remains unchanged. The analysis of neuronal activity reveals that the subject's behavioral response is preceded by the formation of a distributed functional network in the β-frequency band. This network is characterized by high connectivity in the frontal cortex and supposed to subserve a decision-making process. We show that neither the network structure nor the duration of its formation depend on RT and stimulus ambiguity. In turn, RT is related to the moment of time when the β-band functional network emerges. We hypothesize that RT is affected by the processes preceding the decision-making stage, e.g., encoding visual sensory information and extracting decision-relevant features from raw sensory information.
Highlights
When performing a task implying visual information processing and decision-making, the brain dynamically adjusts the structure of its functional network so as to maintain an optimal behavioral performance under the increasing cognitive demand (Parks and Madden, 2013; Davison et al, 2015; Shine and Poldrack, 2018)
Behavioral analysis revealed an increase in reaction time (RT) as the stimulus ambiguity is increased
The observed RT fluctuations are not associated with mental fatigue, because longer RTs dominate at the beginning of the experiment
Summary
When performing a task implying visual information processing and decision-making (perceptual decision-making task), the brain dynamically adjusts the structure of its functional network so as to maintain an optimal behavioral performance under the increasing cognitive demand (Parks and Madden, 2013; Davison et al, 2015; Shine and Poldrack, 2018). Functional networks have different anatomical locations, they interact with each other and overlap during task accomplishing (Xu et al, 2013) In their recent work, Rosenberg et al (2016) demonstrated that brain functional connectivity restored from fMRI during a resting state can predict the subject’s ability to maintain sustained attention during demanding tasks. It was shown that along with slow fatigue-related and demandrelated changes there are spontaneous fluctuations in functional connectivity that affect behavioral performance In this respect, Kucyi et al (2017) evidenced that when the attention level fluctuates during a long-term attention task, different parts of the attention-related network (dorsal-attention and default-mode networks) exhibit antiphase changes in functional connectivity. Slow rhythmic oscillations of sustained attention were detected during a prolonged cognitive load (Helfrich et al, 2018; Maksimenko et al, 2018a, 2019)
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