From brain to blood vessels and back: a noninvasive optical imaging approach

Abstract

Abstract. The seminal work of Grinvald et al. has paved the way for the use of intrinsic optical signals measured with reflection methods for the analysis of brain function. Although this work has focused on the absorption signal associated with deoxygenation, due to its detailed mapping ability and good signal-to-noise ratio, Grinvald's group has also described other intrinsic signals related to increased blood flow, scattering effects directly related to neural activation, and pulsation effects related to arterial function. These intrinsic optical signals can also be measured using noninvasive diffuse optical topographic and tomographic imaging (DOT) methods that can be applied to humans. Here we compare the reflection and DOT methods and the evidence for each type of intrinsic signal in these two domains, with particular attention to work that has been conducted in our laboratory. This work reveals the refined two-way relationship that exists between vascular and neural phenomena in the brain: arterial health is related to normal brain structure and function, both across individuals and across brain regions within an individual, and neural function influences blood flow to specific cortical regions. DOT methods can provide quantitative tools for investigating these relationships in normal human subjects.

Applications of Functional Near-Infrared Spectroscopy (fNIRS) Neuroimaging in Exercise–Cognition Science: A Systematic, Methodology-Focused Review

“…Regarding the temporal window for the analysis, it should be considered that there is in general a certain delay (e.g., ≈6 s) after stimulus representation and the peak of the cortical hemodynamic [34,41,59,131,286,287,288], whereby this latency is influenced by the performed task [289,290], and that the temporal courses of deoxyHb and oxyHb concentration changes are different [290,291,292,293,294,295]. The cortical hemodynamic response does not normally go back to the baseline level before ≈10 s (≈16 s) after stimulus presentation [296,297].…”

“…fNIRS provides some advantages that make it well-situated to investigate the effects of physical activity on cognitive performance and cerebral oxygenation/hemodynamics. Advantages of fNIRS compared to other neuroimaging techniques (e.g., fMRI and PET) are: non-invasiveness, a relatively good spatial (≈1.0–3.0 cm) and temporal resolution (normally up to 10 Hz), portability, a low noise level during operation, relative low acquisition costs, robustness against motion artefacts that make a strict immobilization or sedation of participants unnecessary, the possibility to investigate cortical activity in individuals with metallic implants or claustrophobia, and the opportunity to conduct repeated measures in short time intervals (since no radioactive tracer substance as in PET is used) [21,22,29,30,32,34,38,40,41,52,54,59]. The mentioned advantages make fNIRS eminently suitable for application in special cohorts such as children [29,34] or neurological patients [23,60,61].…”

“…The mentioned advantages make fNIRS eminently suitable for application in special cohorts such as children [29,34] or neurological patients [23,60,61]. Furthermore, while fMRI mainly relies on the paramagnetic properties of deoxyHb, fNIRS can be used to quantify both changes of deoxyHb and of oxyHb [53,54,58,59,62]. The simultaneous assessment of deoxyHb and oxyHb allows the quantification of further markers of cortical activation such as tissue oxygenation (TOI: oxyHb concentration/total hemoglobin concentration) and cortical hemodynamics (blood volume, total hemoglobin concentration (totHb)) [22,30,54,58].…”

Hemodynamic effects of sex and handedness on the Wisconsin Card Sorting Test: the contradiction between neuroimaging and behavioural results

“…However, the biophysical model implemented in fNIRS includes other important neurovascular dynamic factors, such as cerebral blood volume (CBV) and oxygenation (OXY) ( Caldwell et al, 2016 ; Banaji et al, 2008 ) as well as some component of cellular level hemodynamic regulation via several different metabolic pathways ( Hillman, 2014 ; Hamel, 2006 ; Filosa et al, 2016 ; Attwell et al, 2010 ; Ances et al, 2009 ; Walsh, 2016 ). In recent years, a substantial amount of research has been published supporting the ability of astrocytes to modulate vascular tone ( Filosa et al, 2016 ; Ayata & Lauritzen, 2015 ; Bazargani & Attwell, 2016 ; Gratton, Chiarelli & Fabiani, 2017 ). Although auto-regulatory processes of the overall brain tissue blood supply, in general, might be indifferent or partially determined ( Rodriguez et al, 1988 ; Gur et al, 1982 ; Amen et al, 2017 ), the microcirculation at the level of the penetrating arterioles, and capillaries is less well understood and controversial ( Mishra et al, 2016 ; Hall et al, 2014 ).…”

Characterization of a fiber-less, multichannel optical probe for continuous wave functional near-infrared spectroscopy based on silicon photomultipliers detectors: in-vivo assessment of primary sensorimotor response

“…4 O 2 Hb and HHb are the main chromophores that fluctuate in the NIR spectral range and they provide different absorption spectra. These characteristics, together with the water's low absorption and the high diffusive properties of biological tissues, allow estimating O 2 Hb and HHb concentration, and oscillations employing light sources and detectors located on the same investigation surface (the scalp, backscattering geometry 5 ).…”