Prolongation of ERP latency and reaction time (RT) in simultaneous EEG/fMRI data acquisition

Background: Recording EEG and fMRI data simultaneously inside a fully-operating scanner has been recognized as a novel approach in human brain research. Studies have demonstrated high concordance between the EEG signals and hemodynamic response. However, a few studies reported altered cognitive process inside the fMRI scanner such as delayed reaction time (RT) and reduced and/or delayed N100 and P300 event-related brain potential (ERP) components.

New method: The present study investigated the influence of electromagnetic field (static magnetic field, radio frequency (RF) pulse, and gradient switching) and experimental environment on posterior N100 and P300 ERP components in four different settings with six healthy subjects using a visual oddball task: (1) classic fMRI acquisition inside the scanner (e.g., supine position, mirror glasses for stimulus presentation), (2) standard behavioral experiment outside the scanner (e.g., seated position, keyboard response), (3) controlled fMRI acquisition inside the scanner (e.g., organic light-emitting diode (OLED) goggles for stimulus presentation) inside; and (4) modified behavioral experiment outside the scanner (e.g., supine position, OLED goggles).

Results: The study findings indicated that the experimental environment in simultaneous EEG/fMRI acquisition could substantially delay N1P, P300 latency, and RT inside the scanner, and was associated with a reduced N1P amplitude.

Comparison with existing methods: There was no effect of electromagnetic field in the prolongation of RT, N1P and P300 latency inside the scanner. N1P, but not P300, latency was sensitive to stimulus presentation method inside the scanner.

Conclusion: Future simultaneous EEG/fMRI data collection should consider experimental environment in both design and analysis.