Zhongming Liu1, Nanyin Zhang2,3, Cristina Rios1, Lin Yang1, Wei Chen2,3, Bin He1
1Department of Biomedical Engineering, University of Minnesota, Minneapolis, MN, USA; 2Center for Magnetic Resonance Research, University of Minnesota Medical School, Minneapolis, MN, USA; 3Department of Radiology, University of Minnesota Medical School, Minneapolis, MN, USA
To test the linearity of the neurovascular coupling requires quantifying electrophysiological and hemodynamic signals before comparing them against a linear function. The variety of ways for quantifying multimodal signals may partly account for the existing disagreements on the linearity of the neurovascular coupling. In the present study, we modeled the cascaded interactions between stimuli and neural and vascular responses, and proposed a pair of quantitative measures for assessing the relationship between electrophysiological and hemodynamic signals. The neurovascular coupling in the human primary visual cortex was investigated through visual stimulation experiments using a variable visual contrast. Our theoretical and experimental results suggest a linear relationship between the BOLD effect size and the integrated power of the neural impulse response. This is regardless of the presence of the vascular nonlinearity attributed to the vascular refractory effect, since this nonlinear effect can be compensated by using the vascular refractory tuning function.