Characterisation of cortical depth dependent hemodynamics in early human development using high-resolution BOLD fMRI at 7 Tesla.

Motivation: Hemodynamic responses in adults vary across cortical depths, partly due to specific differences in vascular anatomy and physiology. It is unknown how these differences relate to the responses seen in neonates, when the cortex and neurovasculature are rapidly maturing. Goal(s): To characterize the amplitude and timing of the hemodynamic response across cortical depths during the neonatal period. Approach: Cortical depth-dependent hemodynamic responses to sensorimotor stimulation were delineated using GRE-BOLD fMRI in term-aged neonates. Results: A cortical depth-specific profile of key hemodynamic response parameters, including onset and undershoot, was observed in the neonatal cortex that differs from those seen in the adult. Impact: We demonstrate for the first time how developing vascular network may alter hemodynamic response across cortical depths. It illuminates what underlying neurobiology may generate the neonatal specific BOLD signal profile and what components are altered relative to the adult response.