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Neuroimage. 2016 Jan 15;125:556-570. doi: 10.1016/j.neuroimage.2015.10.025. Epub 2015 Oct 17.

A hemodynamic model for layered BOLD signals.

Author information

1
Translational Neuromodeling Unit, Institute for Biomedical Engineering, University of Zurich & ETH Zurich, Switzerland. Electronic address: heinzle@biomed.ee.ethz.ch.
2
FMRIB Centre, Nuffield Department of Clinical Neurosciences, University of Oxford, UK.
3
Radboud University, Donders Institute for Brain, Cognition and Behaviour, Nijmegen, The Netherlands.
4
Translational Neuromodeling Unit, Institute for Biomedical Engineering, University of Zurich & ETH Zurich, Switzerland.
5
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.

Abstract

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.

KEYWORDS:

Bayesian model comparison; Cortical layers; Dynamic causal modeling; Predictive coding; fMRI

[Indexed for MEDLINE]

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