Coherent Spontaneous Hemodynamics in the Human Brain

Abstract

Goal: This work investigates the presence of cerebral hemodynamics (namely Oxy (O) and Deoxy (D) hemoglobin concentrations) that are coherent with spontaneous oscillations in Arterial Blood Pressure (ABP) in 78 healthy subjects during a driving simulation task. Methods: Spatially resolved O and D were measured on the prefrontal cortex with multi-channel near-infrared spectroscopy (NIRS). Wavelet coherence and phasor analysis were performed between O and ABP, and between D and ABP to evaluate the amplitude ratio, phase difference, and duration of significant coherence. Results: In the low-frequency range, oscillations at 0.1 Hz featured significant coherence for the longest time fraction (∼10%–30%). At this frequency, the amplitude ratio and phase difference showed a greater variance across subjects than over cortical locations, and no significant difference between driving tasks and baseline. Conclusions: Measuring low-frequency cerebral hemodynamics that are coherent with systemic ABP holds promise for non-invasive assessment of cerebral perfusion and autoregulation at the cerebral microvascular level.

Keywords

• Near infrared spectroscopy
• spontaneous oscillations
• transfer function analysis
• coherent hemodynamics