Spatial Correspondence Between Functional MRI (fMRI) Activations and Cortical Current Density Maps of Event-Related Potentials (ERP): A Study with Four Tasks

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.

Brain Cortical Mapping by Simultaneous Recording of Functional Near Infrared Spectroscopy and Electroencephalograms from the Whole Brain During Right Median Nerve Stimulation

“…Sources of CSD are supposed to be located in the cortex (Srinivasan 2005 ). Consistent with the present results, previous studies reported that BOLD responses could be estimated from cortical current density distribution in simultaneous fMRI and EEG recording (Liu and He 2008 ; Minati et al 2008 ). These results strongly suggest that the present GLM system using simultaneous NIRS and EEG recording could assess neuro-hemodynamic coupling in the parietal cortex.…”

Methods for Simultaneous EEG-fMRI: An Introductory Review

“…In contrast to fMRI-informed EEG, no specific assumption is made about the spatial organization of activation patterns. This implies that this strategy can yield effects in brain structures or networks that are not necessarily the biophysical generators of, say, the ERP recorded at the scalp (Debener et al, 2005;Minati et al, 2008). One also has to bear in mind that single EEG epochs contain high levels of noise, and single-trial EEG analyses therefore have to rely on techniques that increase the signal-to-noise ratio of individual trials.…”

A Review of the Effectiveness of Neuroimaging Modalities for the Detection of Traumatic Brain Injury

“…272,279,282 Co-registration of data acquired through high-density EEG and/or MEG recordings with structural neuroimaging, such as MRI, provides information about brain activity with spatial resolutions comparable to those of fMRIespecially when guided by fMRI-determined regions of interest for a particular brain state or function. [283][284][285][286][287][288] Additionally, most EEGbased recording systems are relatively inexpensive and portable, compared with currently available structural and functional neuroimaging technologies, making them easily deployable in both clinical and naturalistic (i.e., sports, in-theater) settings. The combination of high temporal resolution, reasonable spatial resolution, flexibility of use, portability, and relatively low cost make clinical electrophysiological techniques appealing methods with which to evaluate persons with TBI and disturbances in psychological health.…”