High-gamma frequency-tagged magnetoencephalography reveals time-resolved task-related functional coupling during...

Fast periodic visual stimulation (FPVS) combined with magnetoencephalography (MEG) provides a powerful approach for extracting frequency-specific brain responses from perceptual processing areas. However, its application in cognitive paradigms, particularly those addressing visuospatial attention, remains underexplored. This study developed an FPVS-based line bisection paradigm to probe visuospatial cognition during visual exploration of the line center using eye movements without manual responses. Line stimuli were spatially modulated at high-gamma frequencies (70-90 Hz), centered at 80 Hz. Source analysis in healthy volunteers revealed a sequential pattern of cortical activation, beginning in the bilateral occipital cortices around 100 ms and subsequently involving right temporoparietal, frontal, and superior parietal regions between approximately 130 and 220 ms. Formal frequency-domain analysis confirmed that 80 Hz Morlet time-frequency power was significantly higher during stimulation than during the pre-stimulus baseline period. Functional connectivity analysis revealed task-related coupling between parietal regions and occipital, frontal, and temporal cortices. These connectivity patterns were anatomically plausible in the context of visuospatial processing. Overall, FPVS-MEG enabled temporally precise mapping of task-related cortical activity and functional coupling during visuospatial processing.