Depth-dependent dynamics of negative BOLD response in the human primary visual cortex

Motivation: The depth-dependent negative BOLD response (NBR), which is used to infer neural suppression, is not fully understood. Goal(s): We demonstrate changes in the dynamics of the NBR with respect to cortical depth in the human visual cortex. Approach: Using a brief unilateral visual stimulus within limited eccentricity, we induce a negative hemodynamic response function (nHRF) and examine its depth dependency on both contralateral and ipsilateral sides. Results: Regardless of the shape of the nHRF, a strong negative response was observed in the superficial gray matter, while a weaker response was seen in the deep gray matter. Impact: This study demonstrated a linear increase in NBR from deep to superficial gray matter, paralleling the depth trend of PBR, and revealed distinct nHRF types with consistent depth trends across both contralateral and ipsilateral side.