Spatial-temporal dynamics of the visual cortex stiffness driven by a flashing checkerboard stimulus

In this work we explore the relationship between localized stiffness changes in the visual cortex and the stimulus switching frequency using a novel functional MRE system (fMRE) capable of probing stiffness changes in the human brain driven by a 12Hz flashing checkerboard stimulus. We measured the mechanical response (fMRE) and BOLD response (fMRI) of the brain to slow (36.96s) switching speeds at timescale typical for classical fMRI experiments and compare the results to faster switching speeds (840ms) where the hemodynamic response (HDR) is entirely saturated, and hence cannot follow anymore the input signal. Combining this with our previous results we observe a characteristic behavior of stiffness changes: for switching speeds where the HDR is saturated the stiffness is higher during the OFF state, while we observe the opposite for switching speeds where the HDR can follow the stimulus. Both differed in baseline to control scans (OFF/OFF).