Linearity of Neural Responses in the Somatosensory Cortex and Their Relationship to BOLD FMRI.

Fan Wang¹, Claire Stevenson¹, Matthew Brookes¹, Peter Morris¹

We use the combination of MEG and fMRI to study the neural basis for BOLD non-linearity. Both nonlinear neural responses to stimuli and nonlinear vascular responses to neural activity may contribute to BOLD non-linearity and the relative contribution of these two effects remains poorly understood. We extended the study of non-linear neural response to both phase locked evoked response and time related beta oscillations in somatosensory cortex. The N20 peak amplitudes show non-linearities with ISI of 0.25-2s, influenced by beta power at the time of stimulation, suggesting that best oscillation should also be considered for BOLD convolution.