A hemodynamic model for layered BOLD signals.
High-resolution blood oxygen level dependent (BOLD) functional magnetic resonance imaging (fMRI) at the sub-millimeter scale has become feasible with recent advances in MR technology. In principle, this would enable the study of layered cortical circuits, one of the fundaments of cortical computation. However, the spatial layout of cortical blood supply may become an important confound at such high resolution. In particular, venous blood draining back to the cortical surface perpendicularly to the layered structure is expected to influence the measured responses in different layers. Here, we present an extension of a hemodynamic model commonly used for analyzing fMRI data (in dynamic causal models or biophysical network models) that accounts for such blood draining effects by coupling local hemodynamics across layers. We illustrate the properties of the model and its inversion by a series of simulations and show that it successfully captures layered fMRI data obtained during a simple visual experiment. We conclude that for future studies of the dynamics of layered neuronal circuits with high-resolution fMRI, it will be pivotal to include effects of blood draining, particularly when trying to infer on the layer-specific connections in cortex--a theme of key relevance for brain disorders like schizophrenia and for theories of brain function such as predictive coding.
Translational Neuromodeling Unit, Institute for Biomedical Engineering, University of Zurich & ETH Zurich, Switzerland. Electronic address: heinzle@biomed.ee.ethz.ch.
Jakob
J
Heinzle
FMRIB Centre, Nuffield Department of Clinical Neurosciences, University of Oxford, UK.
Peter J
PJ
Koopmans
Radboud University, Donders Institute for Brain, Cognition and Behaviour, Nijmegen, The Netherlands.
Hanneke E M
HEM
den Ouden
Translational Neuromodeling Unit, Institute for Biomedical Engineering, University of Zurich & ETH Zurich, Switzerland.
Sudhir
S
Raman
Translational Neuromodeling Unit, Institute for Biomedical Engineering, University of Zurich & ETH Zurich, Switzerland; Wellcome Trust Centre for Neuroimaging, University College London, UK; Max Planck Institute for Metabolism Research, Cologne, Germany.
Klaas Enno
KE
Stephan
D000465:Algorithms; D001921:Brain / Q000098:blood supply*; D001931:Brain Mapping / Q000379:methods*; D006439:Hemodynamics / Q000502:physiology*; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008959:Models, Neurological; D008962:Models, Theoretical; D010100:Oxygen / Q000097:blood
D010100:Oxygen
Bayesian model comparison; Cortical layers; Dynamic causal modeling; Predictive coding; fMRI