Depth-Specific Hypoxic Responses to Spreading Depolarizations in Gyrencephalic Swine Cortex Unveiled by Photoacoustic...

Area of Science:

• Neuroscience
• Cerebrovascular Physiology
• Medical Imaging

Background:

• Spreading depolarizations (SDs) are critical indicators of brain injury and progression of ischemic damage.
• Hemodynamic responses to SDs depend on tissue metabolic state; vasoconstriction leading to hypoxia often signifies poor outcomes.
• The layer-specific hemodynamic changes during SDs in the cortex are not well understood.

Purpose of the Study:

• To investigate depth-specific hemodynamic changes in response to SDs within the swine gyrencephalic brain cortex.
• To characterize the regional cerebral oxygen saturation (rcSO2%) variations across cortical layers during SDs.

Main Methods:

• Utilized a potassium chloride-induced SD model in swine.
• Employed multispectral photoacoustic imaging (PAI) to measure rcSO2% changes at three cortical depths (up to 4 mm).
• Validated SDs using electrocorticography (ECoG).

Main Results:

• 12 distinct rcSO2% responses correlated with ECoG-detected SDs.
• Deeper cortical layers showed a higher incidence of hypoxic responses.
• Superficial cortical layers exhibited predominantly hyperoxic and mixed responses (p < 0.001).

Conclusions:

• This study reveals differential oxygenation patterns across cortical layers following SDs.
• Findings highlight the complex interplay of cerebral hemodynamics and cortical depth in brain injury.
• Provides novel insights into layer-specific vulnerability during spreading depolarizations.