Frequency-specific alterations in global signal topography among individuals with problematic smartphone use

Problematic smartphone use (PSU) has emerged as a significant concern, associated with disruptions in cognitive function, emotional regulation, and neural processing. Previous studies have shown that the global signal (GS) in resting-state functional magnetic resonance imaging (fMRI) influences neuronal activity within the 0.01-0.1 Hz frequency range, yet its spatial pattern in PSU remains poorly understood. In this study, we examined frequency-specific alterations in GS topography in 78 participants (41 PSU and 37 nonPSU individuals) across four frequency bands: slow-2 (0.198-0.25 Hz), slow-3 (0.073-0.198 Hz), slow-4 (0.027-0.073 Hz), and slow-5 (0.01-0.027 Hz). Significant group differences in GS topography were observed, particularly in the left calcarine region. Additionally, significant interaction effects between group and frequency band were identified in the supplementary motor area (SMA). Correlation analyses revealed associations between GS alterations and clinical measures, including the pop-up notification frequency and smartphone usage frequency, especially in the higher frequency bands (slow-2 and slow-3). These findings suggest that PSU is associated with frequency-dependent alterations in GS topography, as supported by a significant Group × Frequency interaction in the SMA-particularly in regions implicated in cognitive control and visual processing. The observed alterations in GS coherence, particularly the elevated coherence at slow-5 and correlations in higher bands, may reflect neural dysfunctions related to attentional control and self-regulation, which are central to the behavioral manifestations of PSU. These results enhance our understanding of the neural mechanisms underlying PSU and emphasize the importance of considering frequency-specific brain activity in PSU research.