title: The effects of hemodynamic lag on functional connectivity and behavior after stroke.
abstract: Stroke disrupts the brain's vascular supply, not only within but also outside areas of infarction. We investigated temporal delays (lag) in resting state functional magnetic resonance imaging signals in 130 stroke patients scanned two weeks, three months and 12 months post stroke onset. Thirty controls were scanned twice at an interval of three months. Hemodynamic lag was determined using cross-correlation with the global gray matter signal. Behavioral performance in multiple domains was assessed in all patients. Regional cerebral blood flow and carotid patency were assessed in subsets of the cohort using arterial spin labeling and carotid Doppler ultrasonography. Significant hemodynamic lag was observed in 30% of stroke patients sub-acutely. Approximately 10% of patients showed lag at one-year post-stroke. Hemodynamic lag corresponded to gross aberrancy in functional connectivity measures, performance deficits in multiple domains and local and global perfusion deficits. Correcting for lag partially normalized abnormalities in measured functional connectivity. Yet post-stroke FC-behavior relationships in the motor and attention systems persisted even after hemodynamic delays were corrected. Resting state fMRI can reliably identify areas of hemodynamic delay following stroke. Our data reveal that hemodynamic delay is common sub-acutely, alters functional connectivity, and may be of clinical importance.
authors.affiliation: Departments of Neurology, Washington University School of Medicine, Washington University, St. Louis, MO, USA siegelj@wusm.wustl.edu.
authors.forename: Joshua S
authors.initials: JS
authors.lastname: Siegel
authors.affiliation: Departments of Neurology, Washington University School of Medicine, Washington University, St. Louis, MO, USA.|Mallinckrodt Institute of Radiology, Washington University School of Medicine, Washington University, St. Louis, MO, USA.
authors.forename: Abraham Z
authors.initials: AZ
authors.lastname: Snyder
authors.affiliation: Departments of Neurology, Washington University School of Medicine, Washington University, St. Louis, MO, USA.
authors.forename: Lenny
authors.initials: L
authors.lastname: Ramsey
authors.affiliation: Departments of Neurology, Washington University School of Medicine, Washington University, St. Louis, MO, USA.
authors.forename: Gordon L
authors.initials: GL
authors.lastname: Shulman
authors.affiliation: Departments of Neurology, Washington University School of Medicine, Washington University, St. Louis, MO, USA.|Mallinckrodt Institute of Radiology, Washington University School of Medicine, Washington University, St. Louis, MO, USA.|Anatomy & Neurobiology at Washington University School of Medicine, Washington University, St. Louis, MO, USA.
authors.forename: Maurizio
authors.initials: M
authors.lastname: Corbetta
mesh_terms: D000328:Adult; D001288:Attention; D001921:Brain / Q000098:blood supply / Q000503:physiopathology; D016022:Case-Control Studies; D002560:Cerebrovascular Circulation; D006439:Hemodynamics / Q000502:physiology*; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D009043:Motor Activity; D009434:Neural Pathways; D020521:Stroke / Q000503:physiopathology* / Q000523:psychology
keywords: Acute stroke; brain ischemia; cerebral blood flow; cerebral hemodynamics; cognitive impairment; functional MRI