Transient functional blood flow change in the human brain measured noninvasively by diffusing-wave spectroscopy

Area of Science:

• Neuroscience
• Biophysics
• Medical Imaging

Background:

• Cortical hemodynamics are crucial for understanding brain function.
• Non-invasive techniques are needed to measure real-time blood flow changes in the visual cortex.

Purpose of the Study:

• To investigate transient blood flow responses in the human visual cortex using multispeckle diffusing-wave spectroscopy (DWS).
• To characterize the temporal and spatial patterns of these blood flow changes during visual stimulation.

Main Methods:

• Multispeckle diffusing-wave spectroscopy (DWS) was employed to measure blood flow transients.
• Stimulation involved 7.5 Hz full-field and checkerboard flickering.
• DWS autocorrelation function decay time (tau(d)) was analyzed.

Main Results:

• A biphasic decay time (tau(d)) behavior was observed.
• An initial rapid increase of tau(d) by ~6% occurred within 2s of stimulation onset.
• A later decrease to ~5% below baseline was observed after 15s, suggesting transient cortical blood flow velocity changes.

Conclusions:

• DWS can detect transient alterations in cortical blood flow velocity.
• The observed initial increase in DWS signal indicates a temporary reduction in blood flow velocity post-stimulation.
• Spatial patterns of this response differ from electroencephalography findings.