Changes in effective diffusivity for oxygen during neural activation and deactivation estimated from capillary...

Area of Science:

• Neuroscience
• Physiology
• Biophysics

Background:

• Cerebral blood flow (CBF) and oxygen extraction fraction (OEF) are linked by oxygen diffusivity (D) in capillaries: OEF = 1 - exp(-D/CBF).
• Effective diffusivity (D) is proportional to microvessel blood volume, reflecting oxygen transport capacity.

Purpose of the Study:

• To investigate how neural activation and deactivation alter effective oxygen diffusivity (D) in the brain.
• To correlate changes in microvessel diameter with alterations in D using in vivo measurements.

Main Methods:

• Utilized two-photon microscopy in awake mice to measure capillary and arteriole diameters in the somatosensory cortex and cerebellum.
• Induce neural activation via sensory stimulation and neural deactivation via crossed cerebellar diaschisis (CCD).

Main Results:

• Sensory stimulation increased D by 10.3 ± 7.3%, while CCD decreased D by -17.5 ± 5.3% in capillaries <6 μm.
• Observed percentage changes in D closely matched previously reported human positron emission tomography data.
• Demonstrated a strong correlation between microvessel diameter changes and D variations.

Conclusions:

• Thin capillaries (<6 μm) appear to be the primary drivers of oxygen transport between blood and brain tissue.
• In vivo mouse models can effectively replicate human brain oxygen transport dynamics.
• Microvessel diameter modulation is a key factor in regulating cerebral oxygen delivery during functional states.