Identification of human sympathetic neurovascular control using multivariate wavelet decomposition analysis

Area of Science:

• Neurovascular physiology
• Autonomic nervous system regulation
• Cerebral blood flow dynamics

Background:

• Cerebral blood flow (CBF) regulation involves myogenic and chemoreflex mechanisms.
• The role of the sympathetic nervous system in dynamic CBF control is debated.
• Accurate analysis requires accounting for confounding factors like end-tidal Pco2 (PetCO2) fluctuations.

Purpose of the Study:

• To investigate the role of human sympathetic neurovascular control in cerebral pressure-flow relations.
• To examine CBF dynamics using advanced signal analysis techniques that control for PetCO2.
• To differentiate sympathetic contributions from myogenic and chemoreflex mechanisms.

Main Methods:

• Employed linear transfer function and multivariate wavelet decomposition analyses.
• Studied 18 healthy participants randomized to alpha-1 adrenergic blockade (Prazosin) or placebo.
• Monitored blood pressure, middle cerebral blood flow velocity, and PetCO2.

Main Results:

• Alpha-1 adrenergic blockade significantly increased wavelet phase synchronization index (PSI) at very low frequencies (≤0.03 Hz).
• Sympathetic blockade's effect on PSI varied with frequency and PetCO2 correction.
• No significant changes were observed in linear transfer function parameters with sympathetic blockade.

Conclusions:

• Very-low-frequency CBF dynamics are influenced by sympathetic nervous system activity in a frequency-dependent manner.
• Sympathetic control interacts with nonlinear and nonstationary relationships between blood pressure and PetCO2.
• Advanced wavelet analysis is crucial for uncovering subtle neurovascular regulatory mechanisms.