Key result
Forepaw stimulation in rats increases local blood flow ~21%, accurately fitting a windkessel model.
A four-element windkessel model provides a simple explanation for transient blood-flow responses in the brain, which is relevant for interpreting BOLD fMRI.
Supports simple modeling of transient cerebral blood flow in rodents; leaves open translation to BOLD fMRI interpretation in humans.
Proper interpretation of BOLD fMRI and other common functional imaging methods requires an understanding of neurovascular coupling. We used laser speckle-contrast optical imaging to measure blood-flow responses in rat somatosensory cortex elicited by brief (2 s) forepaw stimulation. Results show a large increase in local blood flow speed followed by an undershoot and possible late-time oscillations. The blood flow measurements were modeled using the impulse response of a simple linear network, a four-element windkessel. This model yielded excellent fits to the detailed time courses of activated regions. The four-element windkessel model thus provides a simple explanation and interpretation of the transient blood-flow response, both its initial peak and its late-time behavior.
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Khan et al. (2011) studied Healthy (somatosensory blood flow) (n=3). Brief forepaw electrical stimulation vs. Baseline was evaluated on Blood flow response and model fit (fraction of variance explained). Brief forepaw stimulation in rats induced a large increase in local blood flow speed (mean 20.6%) followed by an undershoot, which was accurately modeled by a four-element windkessel linear network.
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