Hemodynamic Traveling Waves in Human Visual Cortex

Abstract

Functional MRI (fMRI) experiments rely on precise characterization of the blood oxygen level dependent (BOLD) signal. As the spatial resolution of fMRI reaches the sub-millimeter range, the need for quantitative modelling of spatiotemporal properties of this hemodynamic signal has become pressing. Here, we find that a detailed physiologically-based model of spatiotemporal BOLD responses predicts traveling waves with velocities and spatial ranges in empirically observable ranges. Two measurable parameters, related to physiology, characterize these waves: wave velocity and damping rate. To test these predictions, high-resolution fMRI data are acquired from subjects viewing discrete visual stimuli. Predictions and experiment show strong agreement, in particular confirming BOLD waves propagating for at least 5–10 mm across the cortical surface at speeds of 2–12 mm s-1. These observations enable fundamentally new approaches to fMRI analysis, crucial for fMRI data acquired at high spatial resolution.

The spatiotemporal hemodynamic response function for depth-dependent functional imaging of human cortex

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Efficient hemodynamic states stimulation using fNIRS data with the extended Kalman filter and bifurcation analysis of balloon model

“…The major assumption is that the venous balloon constitutes the only origin of the change in CBV and [4,5,[8][9][10]. Conservation of mass then defines the change in the normalized blood volume v in the venous balloon as follow: …”

“…In NIR range (650 nm -950 nm), water has relatively low absorption while oxy-and deoxy-hemoglobin have high absorption. Due to these properties, NIR light can penetrate biological tissues in the range of 0.5 -3 cm allowing investigation of relatively deep brain tissues, and ability to differentiate between healthy and diseased tissues [4].…”

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Inference of direct and multistep effective connectivities from functional connectivity of the brain and of relationships to cortical geometry

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