Recruitment patterns of hothubs and dark functional networks correlating activity and connectivity with magnetoencephalography

In functional imaging studies, the activity and functional connectivity of regions of interest (ROIs) are two indexes to measure the importance of ROIs. This study aimed to investigate the activity-connectivity coupling relationships of ROIs during action observation-induced swallowing imagery and non-induced swallowing imagery tasks. Magnetoencephalography data were collected from fourteen healthy young participants. Time-frequency analysis of event-related spectral perturbations was conducted to assess the activity of ROIs during the tasks. Using corrected imaginary phase locking values to construct brain functional networks, network parameters are computed to assess connectivity. The correlation between activity and connectivity was evaluated using Pearson coefficients. Furthermore, the nodes were categorized into hot hubs (strong activity + strong connectivity), nonhub hotspots (strong activity + weak connectivity), cold hubs (weak activity + strong connectivity), and nonhub cold spots (weak activity + weak connectivity) for further analysis, and dark functional networks (subnetworks composed of cold hubs) were detected and analyzed. Both tasks exhibited positive activity-connectivity coupling relationships, however, the coupling strength remained below a moderate level (< 0.6). Notably, both tasks demonstrated limited activation of hot hubs. During the action observation-induced swallowing imagery task, there was a notable increase in the activation of non-hub hotspots within the visual system, extending bilaterally. Additionally, the dark functional network, composed of cold hubs, exhibited increased swallowing-related ROIs in action observation-induced swallowing imagery task. This study provides insights into the activity-connectivity coupling and dark functional network characteristics during swallowing imagery tasks. The findings contribute to our understanding of the neural mechanisms underlying swallowing imagery and may have implications for the development of therapeutic interventions for swallowing disorders.