Spatial Correspondence Between Functional MRI (fMRI) Activations and Cortical Current Density Maps of Event-Related Potentials (ERP): A Study with Four Tasks |
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Authors: | Ludovico Minati Cristina Rosazza Ileana Zucca Ludovico D’Incerti Vidmer Scaioli Maria Grazia Bruzzone |
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Institution: | (1) Science Direction Unit, Fondazione IRCCS Istituto Neurologico “Carlo Besta”, Via Celoria 11, 20133 Milano, MI, Italy;(2) Neuroradiology Department, Fondazione IRCCS Istituto Neurologico “Carlo Besta”, Milan, Italy;(3) Institut des Sciences Cognitives, CNRS, Lyon, France;(4) Neurophysiopathology Department, Fondazione IRCCS Istituto Neurologico “Carlo Besta”, Milan, Italy |
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Abstract: | We investigated the spatial correspondence between functional MRI (fMRI) activations and cortical current density maps of
event-related potentials (ERPs) reconstructed without fMRI priors. The presence of a significant spatial correspondence is
a prerequisite for direct integration of the two modalities, enabling to combine the high spatial resolution of fMRI with
the high temporal resolution of ERPs. Four separate tasks were employed: visual stimulation with a pattern-reversal chequerboard,
recognition of images of nameable objects, recognition of written words, and auditory stimulation with a piano note. ERPs
were acquired with 19 recording channels, and source localisation was performed using a realistic head model, a standard cortical
mesh and the multiple sparse priors method. Spatial correspondence was evaluated at group level over 10 subjects, by means
of a voxel-by-voxel test and a test on the distribution of local maxima. Although not complete, it was significant for the
visual stimulation task, image and word recognition tasks (P < 0.001 for both types of test), but not for the auditory stimulation task. These findings indicate that partial but significant
spatial correspondence between the two modalities can be found even with a small number of channels, for three of the four
tasks employed. Absence of correspondence for the auditory stimulation task was caused by the unfavourable situation of the
activated cortex being perpendicular to the overlying scalp, whose consequences were exacerbated by the small number of channels.
The present study corroborates existing literature in this field, and may be of particular relevance to those interested in
combining fMRI with ERPs acquired with the standard 10-20 system. |
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Keywords: | Event-related potentials Functional MRI Spatial correspondence Visual stimulation Image recognition Word recognition Auditory stimulation |
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