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Investigating the wavelet coherence phase of the BOLD signal

MPS-Authors
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Müller,  Karsten
Department Cognitive Neurology, MPI for Human Cognitive and Brain Sciences, Max Planck Society;

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Lohmann,  Gabriele
Department Cognitive Neurology, MPI for Human Cognitive and Brain Sciences, Max Planck Society;

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Neumann,  Jane
Department Cognitive Neurology, MPI for Human Cognitive and Brain Sciences, Max Planck Society;

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Grigutsch,  Maren
Department Neuropsychology, MPI for Human Cognitive and Brain Sciences, Max Planck Society;

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Mildner,  Toralf
Methods and Development Unit Nuclear Magnetic Resonance, MPI for Human Cognitive and Brain Sciences, Max Planck Society;

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von Cramon,  D. Yves
Department Cognitive Neurology, MPI for Human Cognitive and Brain Sciences, Max Planck Society;

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Citation

Müller, K., Lohmann, G., Neumann, J., Grigutsch, M., Mildner, T., & von Cramon, D. Y. (2004). Investigating the wavelet coherence phase of the BOLD signal. Journal of Magnetic Resonance Imaging, 20(1), 145-152. doi:10.1002/jmri.20064.


Cite as: http://hdl.handle.net/11858/00-001M-0000-0010-BF9D-9
Abstract
Purpose: To investigate the temporal behavior of the blood oxygenation-level dependent (BOLD) signal applying the wavelet coherence phase to functional magnetic resonance imaging (fMRI) data. Materials and Methods: The wavelet coherence phase was computed for a group of four subjects using three functional runs of different visual stimulation lengths. In order to consider the variability of the wavelet coherence phase, a correlation analysis was performed between the variance of the phase shift and the associated activation strength. In activated brain regions, correlation was performed between the mean wavelet coherence phase and the spectral density phase shift. Results: The scalograms of the wavelet coherence phase show the temporal variability of the phase shift between fMRI time series. For brain regions with weakly stationary behavior, the mean wavelet coherence phase supports the results obtained by spectral analyses. Conclusion: The wavelet coherence phase provides a description of the temporal behavior of the BOLD signal even for the nonstationary case. In particular, temporal changes of the phase shift can be investigated. This makes the wavelet coherence phase more suitable for the investigation of BOLD dynamics than an average phase lag obtained by correlation or spectral methods.