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Abstract #0596

Failure of the standard fMRI analysis in the visual cortex using a smooth visual stimulus

David Provencher 1 , Andreas Bartels 2 , Yves Brub-Lauzire 3,4 , and Kevin Whittingstall 4,5

1 Department of Nuclear Medicine and Radiobiology, Universit de Sherbrooke, Sherbrooke, QC, Canada, 2 Werner Reichardt Centre for Integrative Neuroscience, Tbingen, Germany, 3 Department of Electrical and Computer Engineering, Universit de Sherbrooke, Sherbrooke, QC, Canada, 4 Centre d'imagerie molculaire de Sherbrooke (CIMS), Universit de Sherbrooke, Sherbrooke, QC, Canada, 5 Department of Diagnostic Radiology, Universit de Sherbrooke, Sherbrooke, QC, Canada

Typical task-fMRI studies aim to compute brain activation maps through voxel-wise correlation of measured and modeled BOLD timecourses. This usually relies on two hypotheses, namely that 1) neural activity follows the stimulation waveform (e.g. a boxcar function) and that 2) the hemodynamic response function (HRF), relating neural and BOLD activity, follows a canonical model. Here, we acquired sequential EEG-fMRI data in 5 subjects viewing multiple repetitions of a sinusoidally modulated visual stimulus over 8 seconds. Through data analysis and linear deconvolution of HRFs, we show that both hypotheses are inappropriate here, and are therefore not generalizable to slowly changing stimuli.

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