Spatiotemporal variation of the negative hemodynamic response function along the cortical surface of the primary visual cortex in human brain

Motivation: There is limited understanding of the detailed dynamics of the negative BOLD response (NBR). Goal(s): To investigate changes in NBR dynamics relative to cortical distance from the stimulus representation (SR) on the contralateral side and NBR dynamics on the ipsilateral side. Approach: Using a unilateral visual stimulus, we measured the nHRFs (NBR evoked by a brief stimulus) and performed distance analysis along the cortical surface to characterize changes of the nHRF dynamics. Results: Dynamics of the nHRF varies with increasing distance from the SR. Three types of nHRFs are observed with varying proportions with distance from the SR. Impact: An evolution of nHRF dynamics is apparent with distance from the SR. Different types of nHRFs are found, indicating more complex dynamics of the nHRF.