Changes in high-frequency aperiodic 1/f slope and periodic activity reflect post-stimulus functional inhibition in the visual cortex

Abstract

AbstractIt has been shown that cessation of intensive sensory stimulation is associated with a transient increase in functional inhibition in the sensory cortical areas. However, the electrophysiological correlates of this post-stimulus inhibition in the human brain have not been properly investigated.To investigate post-stimulus inhibition, we recorded magnetoencephalogram (MEG) at rest and after cessation of visual stimulation of varying intensity (high-contrast gratings drifting at a slow, medium, or high rate) in 25 healthy women aged 18-40 years. We analyzed condition- and intensity-related changes in MEG parameters sensitive to functional inhibition: periodic alpha-beta power, peak alpha frequency (PAF), and 1/f aperiodic slope. We also investigated the association of these parameters with sensory sensitivity and avoidance assessed by a questionnaire. To evaluate the influence of hormonal status on the studied parameters, participants were examined twice, during the follicular and luteal phases of the menstrual cycle (MC).Regardless of MC phase, increasing intensity of the preceding visual stimulation resulted in increased posterior post-stimulus alpha-beta power, PAF, and a more negative/steeper aperiodic (1/f) slope of the power spectrum in the 35-45 Hz range. Compared to rest, the post-stimulus period was characterized by higher PAF, a steeper 35-45 Hz 1/f slope in posterior cortical areas, and a widespread increase in beta power. While condition- and intensity-dependent changes in alpha-beta power and 1/f slope were correlated, changes in PAF did not correlate with either of them. Greater intensity-dependent increase in visual alpha-beta power predicted higher subjective sensory sensitivity/avoidance, suggesting stronger regulatory top-down modulation of visual cortex in individuals with heightened sensitivity.Our results show that several MEG parameters concordantly indicate a post-stimulus enhancement of inhibition that is proportional to the intensity of the preceding visual stimulation. While post-stimulus changes in alpha-beta power and 1/f slope may share some common mechanisms, changes in PAF reflect a distinct aspect of inhibitory regulation. Our results inform potential inhibition-based biomarkers for clinical and translational research.Key points:The cessation of visual stimulation leads to a transient increase in functional inhibition.Changes in MEG parameters reflect post-stimulus enhancement of inhibition.These changes scale with the intensity of the preceding stimulation.