title: Estimating time-varying brain connectivity networks from functional MRI time series.
abstract: At the forefront of neuroimaging is the understanding of the functional architecture of the human brain. In most applications functional networks are assumed to be stationary, resulting in a single network estimated for the entire time course. However recent results suggest that the connectivity between brain regions is highly non-stationary even at rest. As a result, there is a need for new brain imaging methodologies that comprehensively account for the dynamic nature of functional networks. In this work we propose the Smooth Incremental Graphical Lasso Estimation (SINGLE) algorithm which estimates dynamic brain networks from fMRI data. We apply the proposed algorithm to functional MRI data from 24 healthy patients performing a Choice Reaction Task to demonstrate the dynamic changes in network structure that accompany a simple but attentionally demanding cognitive task. Using graph theoretic measures we show that the properties of the Right Inferior Frontal Gyrus and the Right Inferior Parietal lobe dynamically change with the task. These regions are frequently reported as playing an important role in cognitive control. Our results suggest that both these regions play a key role in the attention and executive function during cognitively demanding tasks and may be fundamental in regulating the balance between other brain regions.
authors.affiliation: Department of Mathematics, Imperial College London, London SW7 2AZ, UK.
authors.forename: Ricardo Pio
authors.initials: RP
authors.lastname: Monti
authors.affiliation: Computational, Cognitive and Clinical Neuroimaging Laboratory, Imperial College London, The Hammersmith Hospital, London W12 0NN, UK.
authors.forename: Peter
authors.initials: P
authors.lastname: Hellyer
authors.affiliation: Computational, Cognitive and Clinical Neuroimaging Laboratory, Imperial College London, The Hammersmith Hospital, London W12 0NN, UK.
authors.forename: David
authors.initials: D
authors.lastname: Sharp
authors.affiliation: Computational, Cognitive and Clinical Neuroimaging Laboratory, Imperial College London, The Hammersmith Hospital, London W12 0NN, UK.
authors.forename: Robert
authors.initials: R
authors.lastname: Leech
authors.affiliation: Department of Mathematics, Imperial College London, London SW7 2AZ, UK.
authors.forename: Christoforos
authors.initials: C
authors.lastname: Anagnostopoulos
authors.affiliation: Department of Mathematics, Imperial College London, London SW7 2AZ, UK; Department of Biomedical Engineering, King's College London, St Thomas' Hospital, London SE1 7EH, UK. Electronic address: giovanni.montana@kcl.ac.uk.
authors.forename: Giovanni
authors.initials: G
authors.lastname: Montana
mesh_terms: D000465:Algorithms; D001921:Brain / Q000502:physiology*; D001931:Brain Mapping / Q000379:methods*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging / Q000379:methods*; D009434:Neural Pathways / Q000502:physiology*