[Paper Review] Feasibility of simultaneous EEG-fMRI at 0.55 T: Recording, Denoising, and Functional Mapping

Parsa Razmara, Takfarinas Medani+7 more|arXiv (Cornell University)|Feb 13, 2026

Functional Brain Connectivity Studies0 citations

TL;DR

The study demonstrates that simultaneous EEG-fMRI is feasible at 0.55T, showing reduced BCG artifacts and viable EEG denoising, with detectable visual BOLD activation and EEG-fMRI coupling.

ABSTRACT

Simultaneous recording of electroencephalography (EEG) and functional MRI (fMRI) can provide a more complete view of brain function by merging high temporal and spatial resolutions. High-field ($\geq$3T) systems are standard, and require technical trade-offs, including artifacts in the EEG signal, reduced compatibility with metallic implants, high acoustic noise, and artifacts around high-susceptibility areas such as the optic nerve and nasal sinus. This proof-of-concept study demonstrates the feasibility of simultaneous EEG-fMRI at 0.55T in a visual task. We characterize the gradient and ballistocardiogram (BCG) artifacts inherent to this environment and observe reduced BCG magnitude consistent with the expected scaling of pulse-related artifacts with static magnetic field strength. This reduction shows promise for facilitating effective denoising while preserving the alpha rhythm and signal integrity. Furthermore, we tested a multimodal integration pipeline and demonstrated that the EEG power envelope corresponds with the hemodynamic BOLD response, supporting the potential to measure neurovascular coupling in this environment. We demonstrate that combined EEG-fMRI at 0.55T is feasible and represents a promising environment for multimodal neuroimaging.

Motivation & Objective

• Assess EEG data quality and artifact profile in 0.55T during simultaneous EEG-fMRI.
• Evaluate the ability to detect task-based BOLD activation in the visual cortex at 0.55T.
• Develop and test an EEG-informed multimodal integration pipeline for 0.55T.
• Demonstrate correspondence between EEG-derived predictors and BOLD signals to validate neurovascular coupling at 0.55T.

Proposed method

• Conduct simultaneous EEG-fMRI at 0.55T with a visual checkerboard task in two healthy adults.
• Record 32-channel MR-compatible EEG and 0.55T fMRI with a 3.0 s TR and 3.3x3.3x4 mm3 voxels.
• Characterize gradient-induced and BCG artifacts across Outside, Scanner OFF, and Scanner ON conditions.
• Apply AAS for GA correction, pulse-artifact subtraction for BCG, and ICA for residual artifact removal.
• Process fMRI with BrainSuite and SPM12; concatenate two 5-minute runs for 10-minute analysis.
• Construct EEG-informed predictor from 12 Hz SSVEP power at Oz and convolve with HRF; correlate with voxelwise BOLD.
• Compare EEG-informed maps with standard boxcar HRF models to assess multimodal coupling.

Figure 1: (A) Schematic of the simultaneous EEG-fMRI setup showing synchronization between the MRI trigger and the BrainVision recorder. (B) Protocol overview for Outside, Scanner OFF, and Scanner ON conditions.

Experimental results

Research questions

• RQ1 Can EEG data be reliably denoised and preserved for analysis in a 0.55T MRI environment?
• RQ2 Is there significant BOLD activation in the visual cortex during a 0.55T fMRI task with extended (10-minute) runs?
• RQ3 Does EEG-derived 12 Hz power envelope reliably predict BOLD signals in the visual cortex at 0.55T?
• RQ4 Do EEG-informed predictors and standard GLM-based models show spatial correspondence in the 0.55T setting?

Key findings

• BCG artifact magnitude is reduced at 0.55T compared with higher-field systems, aiding denoising.
• 10-minute concatenated runs yield significant visual cortex activation localized to V1 and surrounding areas (mean t ~ 9.0, p<0.05 FDR).
• EEG spectral analyses show preservation of alpha rhythm (8–13 Hz) after artifact removal and clear 12 Hz task-related responses (with 24 Hz and 36 Hz harmonics).
• EEG-informed predictor based on 12 Hz power correlates with BOLD maps similarly to the standard boxcar model, indicating functional neurovascular coupling.
• Topographical SSVEP activation is focal over occipital electrodes (Oz, O1, O2), preserving spatial specificity after denoising.
• The study provides proof-of-concept that simultaneous EEG-fMRI at 0.55T is feasible and supports multimodal functional mapping and neurovascular coupling.

Figure 2: Representative example of EEG signal showing the raw signal across conditions: (A) Outside scanner, (B) Scanner OFF, (C) Scanner ON, and (D) Final cleaned data after artifact subtraction.