Neurovascular coupling in terms of a control system: Validation of a second-order linear system model

Neurovascular coupling (NC) adapts cerebral blood flow to cortical activity . Functional transcranial Doppler (f-TCD) investigations revealed a typical time course of evoked blood how responses with an initial overshoot and a stabilization at a lower, but stable, level, This blood Bow reaction can be described in terms of a control-system model, We tested reliability and va lidity of this new approach using different stimulation paradigms, The P2 s egment of the posterior cerebral artery was insonated in 14 healthy volunte ers and, subsequently, NC was stimulated using two tests, a checkerboard st imulus of 1 s with different repetition rates and a reading test. Data were analyzed according to algorithms of control-system theory. The reading tes t was used to measure test reliability and side differences, A second-order linear system can describe blood flow regulation of NC. Different stimulat ion protocols of the checkerboard test and the related evoked blood flow cu rves could he described by the same control-system model. Further, there we re no differences between the checkerboard and reading test nor between rig ht and Left side or test and retest of the reading test, NC can be describe d in a much more detailed manner using control-system analysis. We were abl e to show that blood flow response due to different visual stimuli follow o ne common control-system model. Unlike quantification of NC using overshoot , parameters of the control system have smaller SDs, increasing the statist ical power and, thereby, usefulness: of f-TCD as a diagnostic instrument. ( E-mail: Manfred.Kaps @ Neuro.med.uni-Giessen.de) (C) 2001 World Federation for Ultrasound in Medicine & Biology.