Ashish Kaul Sahib1,2,3,4, Klaus Mathiak5, Michael Erb2, Adham Elshahabi3,4,6, Silke Klamer3, Klaus Scheffler1,2,7, Niels K Focke1,3, Thomas Ethofer1,2,8. 1. Werner Reichardt Centre for Integrative Neuroscience, Tübingen, Germany. 2. Department of Biomedical Magnetic Resonance, University Hospital Tübingen, Tübingen, Germany. 3. Department of Neurology/Epileptology, University Hospital Tübingen and Hertie Institute of Clinical Brain Research, Tübingen, Germany. 4. Graduate School of Neural and Behavioural Sciences/International Max Planck Research School, University of Tübingen, Tübingen, Germany. 5. Department of Psychiatry, Psychotherapy and Psychosomatics, University Hospital Aachen, Aachen, Germany. 6. MEG-Center, University of Tübingen, Tübingen, Germany. 7. Max-Planck-Institute for Biological Cybernetics, Tübingen, Germany. 8. Department of General Psychiatry, University Hospital Tübingen, Tübingen, Germany.
Abstract
PURPOSE: 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. METHODS: 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. RESULTS: 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. CONCLUSION: 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.
PURPOSE: 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. METHODS: 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. RESULTS: 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. CONCLUSION: 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.
Authors: Logan T Dowdle; Geoffrey Ghose; Clark C C Chen; Kamil Ugurbil; Essa Yacoub; Luca Vizioli Journal: Prog Neurobiol Date: 2021-09-04 Impact factor: 11.685
Authors: Lena Schwarz; Benjamin Kreifelts; Dirk Wildgruber; Michael Erb; Klaus Scheffler; Thomas Ethofer Journal: PLoS One Date: 2019-04-23 Impact factor: 3.240