Multivariate modeling of cognitive-motor stimulation on neurovascular coupling: transcranial Doppler used to characterize myogenic and metabolic influences

Panerai RB, Eyre M, Potter JF. Multivariate modeling of cognitive-motor stimulation on neurovascular coupling: transcranial Doppler used to characterize myogenic and metabolic influences. Am J Physiol Regul Integr Comp Physiol 303: R395-R407, 2012. First published June 20, 2012; doi:10.1152/ajpregu.00161.2012.-Neural activation induces changes in cerebral blood flow velocity (CBFV) with separate contributions from resistance-area product (V-RAP) and critical closing pressure (V-CrCP). We modeled the dependence of V-RAP and V-CrCP on arterial blood pressure (ABP), end-tidal CO2 (EtCO2), and cognitive stimulation to test the hypothesis that V-RAP reflects myogenic activity while V-CrCP reflects metabolic pathways. In 14 healthy subjects, CBFV was measured with transcranial Doppler ultrasound, ABP with the Finapres device and EtCO2 with infrared capnography. Two different paradigms (word or puzzle) were repeated 10 times (30 s on-off), and the corresponding square-wave signal was used, together with ABP and EtCO2, as inputs to autoregressive-moving average (ARMA) models, which allowed identification of the separate contributions of the three inputs to either V-RAP or V-CrCP. For both paradigms, the contribution of ABP was mainly manifested through V-RAP (P < 0.005 for word; P < 0.004 for puzzle), while stimulation mainly contributed to V-CrCP (P < 0.002 for word; P < 0.033, for puzzle). The contribution of EtCO2 was relatively small (< 10%) with greater contribution to V-CrCP (P < 0.01 for puzzle; not significant for word). Separate step responses were also obtained for each of the three inputs. ARMA modeling of V-RAP and V-CrCP allows the separation of the effects of cerebral autoregulation and CO2 reactivity from the main effects of cognitive-motor stimulation and have the potential to improve the diagnostic value of neurovascular coupling testing in physiological and clinical studies.