Abstract #0510

Neural and Vascular Response Nonlinearity in Human Visual Cortex

Zhongming Liu¹, Cristina Rios¹, Lin Yang¹, Nanyin Zhang^2,3, Wei Chen^2,3, 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

The BOLD nonlinearity may reflect a nonlinear neural response to stimuli and/or a nonlinear vascular response to neural activity. To pinpoint the origin of the BOLD nonlinearity, we investigated the nonlinear effects of neural and vascular responses to sustained visual stimuli with variable temporal frequency ranging from 1/6 to 25 Hz. Using scalp EEG, we found the neural response nonlinearity existed only at very short ISI (<200 ms). Using fMRI, we observed the BOLD nonlinearity for ISI between 0.25 and 4 sec. Such nonlinearity has an exclusively vascular origin and is attributed to the vascular refractory effect instead of the vascular saturation effect.