Myelination selectively modulates BOLD signal in white matter

Area of Science:

• Neuroscience
• Biophysics
• Neuroimaging

Background:

• Blood oxygenation level dependent (BOLD) signals are increasingly detected in white matter (WM).
• The biophysical origins and functional significance of WM BOLD signals are not well understood.
• Understanding WM BOLD signals is crucial for a comprehensive view of brain activity.

Purpose of the Study:

• To investigate the biophysical origins of BOLD signals in WM.
• To identify factors modulating WM BOLD signals.
• To link WM BOLD signal characteristics to microstructural, hemodynamic, and metabolic properties.

Main Methods:

• Integration of multimodal datasets.
• Analysis of resting-state BOLD signals.
• Empirical verification of theoretical predictions.
• Examination of optic nerve images in human subjects.

Main Results:

• Myelination selectively influences the fractional amplitude of low-frequency fluctuations (fALFF) in WM BOLD signals.
• Myelin content and fiber type (association vs. projection) modulate BOLD signal temporal spectra and hemodynamic responses.
• BOLD signal power relates to cerebral blood volume, flow, oxygen extraction, and metabolic rate of oxygen consumption.
• Visual stimulus-evoked BOLD activations in the optic nerve localize to unmyelinated portions.

Conclusions:

• Myelin plays a critical role in shaping BOLD signals in WM.
• WM BOLD signal characteristics are dependent on microstructural features like myelination and fiber type.
• These findings provide a deeper understanding of the functional role of WM and its hemodynamic and metabolic underpinnings.