This project explores the potential of a novel approach to functional studies of the brain with near-infrared spectroscopy. We hypothesize that the phase relationship between oscillations of cerebral oxy-hemoglobin and deoxy-hemoglobin concentrations provide information about (1) the interplay of hemodynamic and oxygenation-related processes that are associated with brain activation, and (2) functional connectivity networks involving distinct cortical areas. Specifically, in this project we will perform a new analysis of data collected previously in a full-night sleep study using a novel phasor-based analysis and representation of hemodynamic oscillations. This new analysis will allow us to test the hypothesis that hemodynamic conditions associated with different sleep stages induce different phase relationship between spontaneous oscillations of oxy-hemoglobin and deoxy-hemoglobin concentrations at frequencies around 0.1 Hz (Mayer waves). We will also test the hypothesis that oxy-hemoglobin and deoxy-hemoglobin concentration changes have different relative phases depending on the cortical area activated and/or the stimulation protocol. Finally, we will perform pilot measurements to test the potential of this new phase-based method in studying functional connectivity networks in the brain. This project can lead to a novel approach to functional brain studies, and explores signals that are not accessible with functional magnetic resonance imaging, involving both paramagnetic and diamagnetic hemoglobin species.
We propose a novel approach to near-infrared functional imaging based on the phase of oscillations of oxy- and deoxy-hemoglobin tissue concentrations. This approach will provide information on the spatial and temporal interplay of hemodynamic and metabolic processes occurring in resting and activated states of the brain. Such information can play a critical role in advancing the understanding of neurovascular coupling, functional connectivity, and cerebral autoregulation, all critical aspects for the development of a significant functional imaging tool.
|Fantini, Sergio (2014) Dynamic model for the tissue concentration and oxygen saturation of hemoglobin in relation to blood volume, flow velocity, and oxygen consumption: Implications for functional neuroimaging and coherent hemodynamics spectroscopy (CHS). Neuroimage 85 Pt 1:202-21|
|Pierro, Michele L; Hallacoglu, Bertan; Sassaroli, Angelo et al. (2014) Validation of a novel hemodynamic model for coherent hemodynamics spectroscopy (CHS) and functional brain studies with fNIRS and fMRI. Neuroimage 85 Pt 1:222-33|
|Hallacoglu, Bertan; Sassaroli, Angelo; Fantini, Sergio (2013) Optical characterization of two-layered turbid media for non-invasive, absolute oximetry in cerebral and extracerebral tissue. PLoS One 8:e64095|
|Sassaroli, Angelo; Martelli, Fabrizio (2012) Equivalence of four Monte Carlo methods for photon migration in turbid media. J Opt Soc Am A Opt Image Sci Vis 29:2110-7|
|Hallacoglu, Bertan; Sassaroli, Angelo; Wysocki, Michael et al. (2012) Absolute measurement of cerebral optical coefficients, hemoglobin concentration and oxygen saturation in old and young adults with near-infrared spectroscopy. J Biomed Opt 17:081406-1|
|Pierro, Michele L; Sassaroli, Angelo; Bergethon, Peter R et al. (2012) Phase-amplitude investigation of spontaneous low-frequency oscillations of cerebral hemodynamics with near-infrared spectroscopy: a sleep study in human subjects. Neuroimage 63:1571-84|
|Sassaroli, Angelo (2011) Fast perturbation Monte Carlo method for photon migration in heterogeneous turbid media. Opt Lett 36:2095-7|