Exploring Resting-State Hemodynamic Oscillations in Cerebral and Extracerebral Tissue by TD fNIRS

In this study, we investigate resting-state hemodynamic oscillations in both cerebral and extracerebral compartments by using time-domain functional near-infrared spectroscopy (TD fNIRS) data acquired with high sampling rate (20 Hz) on the frontal cortex of 16 healthy adults. The improved sampling rate with respect to previous devices allowed for data analysis in the frequency space. We considered these oscillations both in normal breathing condition and during a forced slow breathing protocol, designed to induce a perturbation of the resting state. Our results show the feasibility of in-vivo detection of hemodynamic oscillations in both compartments with a single source-detector distance. Additionally, during the forced slow breathing task we observed enhanced respiratory-driven modulation and increased synchronization between cardiac and respiratory-related oscillations. Simultaneously, we observed differences within lower frequency regions, which suggest changes occurring in local vascular tone regulation mechanisms.