Removal of pulse artefact from EEG data recorded in MR environment at 3T. Setting of ICA parameters for marking artefactual components: application to resting-state data.

Eleonora Maggioni,Anna M Bianchi,Jorge Arrubla,Michela Tosetti,Jürgen Dammers,Tracy Warbrick,Gianluigi Reni,N Jon Shah,Irene Neuner

doi:10.1371/journal.pone.0112147

Abstract

Simultaneous electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) allow for a non-invasive investigation of cerebral functions with high temporal and spatial resolution. The main challenge of such integration is the removal of the pulse artefact (PA) that affects EEG signals recorded in the magnetic resonance (MR) scanner. Often applied techniques for this purpose are Optimal Basis Set (OBS) and Independent Component Analysis (ICA). The combination of OBS and ICA is increasingly used, since it can potentially improve the correction performed by each technique separately. The present study is focused on the OBS-ICA combination and is aimed at providing the optimal ICA parameters for PA correction in resting-state EEG data, where the information of interest is not specified in latency and amplitude as in, for example, evoked potential. A comparison between two intervals for ICA calculation and four methods for marking artefactual components was performed. The performance of the methods was discussed in terms of their capability to 1) remove the artefact and 2) preserve the information of interest. The analysis included 12 subjects and two resting-state datasets for each of them. The results showed that none of the signal lengths for the ICA calculation was highly preferable to the other. Among the methods for the identification of PA-related components, the one based on the wavelets transform of each component emerged as the best compromise between the effectiveness in removing PA and the conservation of the physiological neuronal content.

Highlights

The combination of electroencephalography (EEG) and functional magnetic resonance imaging can provide a noninvasive comprehensive view of brain activity with high temporal (EEG) and spatial resolution
Despite its high temporal resolution, which is in the order of tens of milliseconds, the EEG suffers from the spatial inverse problem, related to the difficulty in inferring the spatial location of neuronal sources in the brain from the potentials recorded at scalp level [1,2]
The functional magnetic resonance imaging (fMRI) technique based on blood oxygen level-dependent (BOLD) contrast gives information about the hemodynamic processes associated with the neuronal activity

Summary

Introduction

The combination of electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) can provide a noninvasive comprehensive view of brain activity with high temporal (EEG) and spatial (fMRI) resolution. The EEG technique gives a measure of the synchronized electrical activity of large populations of neurons. Despite its high temporal resolution, which is in the order of tens of milliseconds, the EEG suffers from the spatial inverse problem, related to the difficulty in inferring the spatial location of neuronal sources in the brain from the potentials recorded at scalp level [1,2]. The fMRI technique based on blood oxygen level-dependent (BOLD) contrast gives information about the hemodynamic processes associated with the neuronal activity. The BOLD measure is extended to the whole brain and has a spatial resolution in the order of mm, but suffers from an ill-posed temporal problem, as it is hard to extract the timings of events that caused the measured hemodynamic modifications [3]. It is worth mentioning the pre-surgical evaluation for epileptic diseases [4], the investigation of neurovascular coupling [5,6,7] and connectivity studies [8,9,10]

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