Markuerkiaga, I. , Barth, M. & Norris, D.
Donders Institute for Cognitive Neuroscience, Nijmegen, Netherlands
The blood-oxygen-level dependent (BOLD) signal is a consequence of neural activity and driven by changes in blood volume, flow and metabolic rate of oxygen consumption. Veins perpendicular to the cortex carry blood through and from all the cortical layers downstream from the layer they originate from. Therefore, neural activation in one layer results in a BOLD signal not only in that layer but also in downstream layers.
In this work we developed a simplified model of cortical vasculature to obtain the characteristics of the vasculature at different cortical depths. Based on these characteristics, we modeled the BOLD signal across the cortex as a volume weighted sum of intravascular and extravascular contribution at baseline and activation for Gradient Echo (GE) and Spin Echo (SE) sequences at 7T. We then estimated the contribution of upstream layers in the predicted laminar BOLD.
The results of the simulation show that, under the assumption of equal neural activation and vascular reactivity across the cortical depth, SE-BOLD is rather laminar specific, as it is driven by the vessels in the laminar mesh. GE BOLD, on the contrary, is dominated by ICVs and the spatial specificity of the measured signal is poorer as layers approach the cortical surface, where it is highly inspecific.
Future developments of this work will be aimed at predicting the cortical layer specific PSF of the BOLD signal under realistic activation patterns.
This work was supported by the Initial Training Network in Ultra-High Field Magnetic Resonance Imaging (FP7-People-ITN-2012, ref. number: 3167167).