Dynamic Changes in Brain Functional Connectivity during Concurrent Dual-Task Performance

This study investigated the spatial, spectral, temporal and functional proprieties of functional brain connections involved in the concurrent execution of unrelated visual perception and working memory tasks. Electroencephalography data was analysed using a novel data-driven approach assessing source coherence at the whole-brain level. Three connections in the beta-band (18–24 Hz) and one in the gamma-band (30–40 Hz) were modulated by dual-task performance. Beta-coherence increased within two dorsofrontal-occipital connections in dual-task conditions compared to the single-task condition, with the highest coherence seen during low working memory load trials. In contrast, beta-coherence in a prefrontal-occipital functional connection and gamma-coherence in an inferior frontal-occipitoparietal connection was not affected by the addition of the second task and only showed elevated coherence under high working memory load. Analysis of coherence as a function of time suggested that the dorsofrontal-occipital beta-connections were relevant to working memory maintenance, while the prefrontal-occipital beta-connection and the inferior frontal-occipitoparietal gamma-connection were involved in top-down control of concurrent visual processing. The fact that increased coherence in the gamma-connection, from low to high working memory load, was negatively correlated with faster reaction time on the perception task supports this interpretation. Together, these results demonstrate that dual-task demands trigger non-linear changes in functional interactions between frontal-executive and occipitoparietal-perceptual cortices.

本研究探究了并行执行无关视觉感知与工作记忆任务时所涉及的功能性脑连接的空间、频谱、时域与功能特性。本研究采用一种全新的数据驱动方法，对脑电图（Electroencephalography, EEG）数据进行分析，以评估全脑层面的源相干性。β频段（18–24 Hz）内的3处脑连接与γ频段（30–40 Hz）内的1处脑连接，其特性受双任务表现调控。与单任务条件相比，双任务条件下两处背侧额叶-枕叶连接的β相干性有所提升，且在低工作记忆负荷试次中相干性达到最高。与之相反，一处前额叶-枕叶功能连接的β相干性，以及一处下额叶-枕顶叶功能连接的γ相干性，并未因第二项任务的加入而受到影响，仅在高工作记忆负荷条件下才表现出相干性升高。对相干性随时间变化的分析表明，背侧额叶-枕叶β连接与工作记忆维持相关，而前额叶-枕叶β连接与下额叶-枕顶叶γ连接则参与并行视觉加工的自上而下调控。随着工作记忆负荷从低升高，该γ连接的相干性有所提升，且这一变化与感知任务中更快的反应时呈负相关，这一发现佐证了上述推论。综上，上述结果表明，双任务需求会引发额叶执行皮层与枕顶叶感知皮层之间的功能性交互产生非线性变化。