Abstract
Billions of neurons in the human brain form neural networks with oscillation rhythms. Infra-slow oscillation (ISO) presents three main physiological sources: endogenic, neurogenic, and myogenic vasomotions. Having an in vivo methodology for the absolute quantification of ISO from the human brain can facilitate the detection of brain abnormalities in cerebral hemodynamic and metabolic activities. In this study, we introduced a novel measurement-plus-analysis framework for the non-invasive quantification of prefrontal ISO by (1) taking dual-channel broadband near infrared spectroscopy (bbNIRS) measurements from 12 healthy humans during a 6-min rest and 4-min post transcranial photobiomodulation (tPBM) and (2) performing wavelet transform coherence (WTC) analysis on the measured time series data. The WTC indexes (IC, between 0 and 1) enabled the assessment of ipsilateral hemodynamic-metabolic coherence and bilateral functional connectivity in each ISO band of the human prefrontal cortex. At rest, bilateral hemodynamic connectivity was consistent across the three ISO bands (IC ≅ 0.66), while bilateral metabolic connectivity was relatively weaker. For post-tPBM/sham comparison, our analyses revealed three key findings: 8-min, right-forehead, 1064-nm tPBM (1) enhanced the amplitude of metabolic oscillation bilaterally, (2) promoted the bilateral metabolic connectivity of neurogenic rhythm, and (3) made the main effect on endothelial cells, causing alteration of hemodynamic-metabolic coherence on each side of the prefrontal cortex.
Highlights
The human brain accounts for 20% of the oxygen consumption and 25% of the glucose utilization in the human body, while it constitutes only 2% of the total body weight [1,2]
Since no significant difference existed between these two sets of baseline parameters, they were pooled as one grant group with a sample size of 24 for infra-slow oscillation (ISO) analyses, followed by further quantifications of bilateral functional connectivity and cerebral hemodynamicmetabolic coherence based on wavelet transform coherence (WTC) analysis
We introduced the spectral oscillation amplitude and coherence of blood oxygenation (i.e., ∆[HbO]) and oxidized cytochrome c oxidase (i.e., ∆[oxCCO]) non-invasively measured by broadband near infrared spectroscopy (bbNIRS) from the human forehead, demonstrating the high feasibility of bbNIRS to serve as a new monitoring device for quantifying cerebral hemodynamic and metabolic infraslow activities (CMIA) of in the human brain at rest
Summary
The human brain accounts for 20% of the oxygen consumption and 25% of the glucose utilization in the human body, while it constitutes only 2% of the total body weight [1,2]. Cerebral energy metabolism is highly mediated by the vascular oxygen supply and neuronal/cellular oxidative respiration in the human brain [3,4]. The detailed mechanism of human cerebral metabolism is not fully understood, one major source was found to be the spontaneous oscillations originated from the blood vessel wall, called the vasomotion [5,6,7,8,9], which has an infra-slow oscillation (ISO) within 0.005–0.2 Hz [10,11]. Cerebral metabolic activities with ISO are closely related to human cognitive functions [12]. It is beneficial to quantify cerebral metabolism in the ISO range for a better understanding of neurophysiology and potential causes of diseases
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