Noninvasive detection of functional brain activity with near-infrared diffusing-wave spectroscopy.

Area of Science:

• Neuroscience
• Biophysics
• Medical Imaging

Background:

• The somato-motor cortex is crucial for motor control.
• Understanding brain activation during motor tasks is essential for neuroscience research.
• Near-infrared light scattering techniques offer non-invasive methods for brain activity monitoring.

Purpose of the Study:

• To investigate brain activation in the somato-motor cortex during a finger opposition task using diffusing-wave spectroscopy (DWS).
• To quantitatively assess changes in cortical optical and dynamical properties during motor activity.
• To explore the relationship between motor task performance and cortical blood flow.

Main Methods:

• Utilized near-infrared diffusing-wave spectroscopy (DWS) to measure temporal autocorrelation functions of scattered light.
• Analyzed DWS data from 11 right-handed volunteers performing finger opposition tasks with alternating rest periods.
• Applied an analytical theory for a three-layer geometry (scalp, skull, cortex) to estimate the diffusion coefficient.

Main Results:

• Observed an increased cortical diffusion coefficient during the finger opposition task.
• Detected a stronger increase in the contralateral hemisphere compared to the ipsilateral hemisphere.
• Results showed consistency with known brain hemispheric asymmetry in right-handed individuals.

Conclusions:

• The increase in cortical diffusion coefficient during motor tasks is attributed to functional increases in cortical blood flow.
• Findings support the role of vasodilation in mediating increased blood flow during motor activity.
• DWS is a viable technique for detecting functional changes in the somato-motor cortex.