title: Effect of temporal resolution and serial autocorrelations in event-related functional MRI.
abstract: To assess the impact of colored noise on statistics in event-related functional MRI (fMRI) (visual stimulation using checkerboards) acquired by simultaneous multislice imaging enabling repetition times (TRs) between 2.64 to 0.26 s.
  
  
  
  T-values within the visual cortex obtained with analysis tools that assume a first-order autoregressive plus white noise process (AR(1)+w) with a fixed AR coefficient versus higher-order AR models with spatially varying AR coefficients were compared. In addition, dependency of T-values on correction of physiological noise (respiration, heart rate) was evaluated.
  
  
  
  Optimal statistical power was obtained for a TR of 0.33 s, but T-values as obtained by AR(1)+w models were strongly dependent on the predefined AR coefficients in fMRI with short TRs which required higher-order AR models to achieve stable statistics. Direct estimation of AR coefficients revealed the highest values within the default mode network while physiological noise had little influence on statistics in cortical structures.
  
  
  
  Colored noise in event-related fMRI obtained at short TRs originates mainly from neural sources and calls for more sophisticated correction of serial autocorrelations which cannot be achieved with standard methods relying on AR(1)+w models with globally fixed AR coefficients. Magn Reson Med 76:1805-1813, 2016. © 2016 International Society for Magnetic Resonance in Medicine.
authors.affiliation: Werner Reichardt Centre for Integrative Neuroscience, Tübingen, Germany.|Department of Biomedical Magnetic Resonance, University Hospital Tübingen, Tübingen, Germany.|Department of Neurology/Epileptology, University Hospital Tübingen and Hertie Institute of Clinical Brain Research, Tübingen, Germany.|Graduate School of Neural and Behavioural Sciences/International Max Planck Research School, University of Tübingen, Tübingen, Germany.
authors.forename: Ashish Kaul
authors.initials: AK
authors.lastname: Sahib
authors.affiliation: Department of Psychiatry, Psychotherapy and Psychosomatics, University Hospital Aachen, Aachen, Germany.
authors.forename: Klaus
authors.initials: K
authors.lastname: Mathiak
authors.affiliation: Department of Biomedical Magnetic Resonance, University Hospital Tübingen, Tübingen, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Erb
authors.affiliation: Department of Neurology/Epileptology, University Hospital Tübingen and Hertie Institute of Clinical Brain Research, Tübingen, Germany.|Graduate School of Neural and Behavioural Sciences/International Max Planck Research School, University of Tübingen, Tübingen, Germany.|MEG-Center, University of Tübingen, Tübingen, Germany.
authors.forename: Adham
authors.initials: A
authors.lastname: Elshahabi
authors.affiliation: Department of Neurology/Epileptology, University Hospital Tübingen and Hertie Institute of Clinical Brain Research, Tübingen, Germany.
authors.forename: Silke
authors.initials: S
authors.lastname: Klamer
authors.affiliation: Werner Reichardt Centre for Integrative Neuroscience, Tübingen, Germany.|Department of Biomedical Magnetic Resonance, University Hospital Tübingen, Tübingen, Germany.|Max-Planck-Institute for Biological Cybernetics, Tübingen, Germany.
authors.forename: Klaus
authors.initials: K
authors.lastname: Scheffler
authors.affiliation: Werner Reichardt Centre for Integrative Neuroscience, Tübingen, Germany.|Department of Neurology/Epileptology, University Hospital Tübingen and Hertie Institute of Clinical Brain Research, Tübingen, Germany.
authors.forename: Niels K
authors.initials: NK
authors.lastname: Focke
authors.affiliation: Werner Reichardt Centre for Integrative Neuroscience, Tübingen, Germany.|Department of Biomedical Magnetic Resonance, University Hospital Tübingen, Tübingen, Germany.|Department of General Psychiatry, University Hospital Tübingen, Tübingen, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Ethofer
mesh_terms: D000465:Algorithms; D016477:Artifacts; D001921:Brain / Q000502:physiology*; D001931:Brain Mapping / Q000379:methods; D005074:Evoked Potentials, Visual / Q000502:physiology*; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D059629:Signal-To-Noise Ratio; D062211:Spatio-Temporal Analysis; D013223:Statistics as Topic; D014793:Visual Cortex / Q000502:physiology*; D014796:Visual Perception / Q000502:physiology*
keywords: autoregressive models; event-related fMRI; fast fMRI; serial autocorrelation; simultaneous multislice echo planar imaging