Arteries dominate volume changes during brief functional hyperemia: evidence from mathematical modelling

Area of Science:

• Neuroscience
• Physiology
• Biophysics

Background:

• Neural activity drives rapid, localized changes in cerebral blood flow and volume.
• Existing research presents conflicting evidence regarding the role of post-arteriole vessels in these hemodynamic responses.

Purpose of the Study:

• To reconcile conflicting observations on cerebral hemodynamic responses using a novel mathematical model.
• To investigate the contribution of different vessel types to blood flow and volume changes during neural activation.

Main Methods:

• Developed a mathematical model of the hemodynamic response, employing both 'top-down' and 'bottom-up' approaches.
• Simulated scenarios with and without dilation in post-arteriole vessels to predict physiological changes.
• Validated model predictions against experimental observations at various scales.

Main Results:

• Model predictions for blood flow, volume, velocity, and vessel diameter changes aligned with experimental data.
• The model predicted small, slow increases in capillary and venous diameter, consistent with in vivo findings.
• Blocking dilation in post-arteriole vessels resulted in inaccurate volume predictions.

Conclusions:

• Arterial dilation accounts for the majority of blood volume increases during brief functional activation.
• Capillary and venous dilation become increasingly significant during extended neural stimulation.
• Accurate interpretation of neurovascular imaging modalities requires consideration of these vessel dynamics.