Real-time rejection of gradient and pulse related artefact (GRA and PRA) from electroencephalographic signals recorded during functional magnetic resonance imaging (fMRI)

Electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) are two imaging techniques used to study the dynamical activity of the human brain. Although complementary, i.e. EEG has a high temporal resolution while fMRI provides precise volumic information, the simultaneous use of both techniques introduces large artefacts in the EEG recordings. These artefacts are consequences of the Faraday’s induction law. Indeed, EEG wires constitutes loop and during fMRI acquisition the magnetic field within the MR scanner changes continuously and abruptly causing the “gradient related artefact” (GRA). Similarly, at each heartbeat, the blood passing through the arteries make the scalp surface pulse slightly, and the entire human body moves slightly causing the “pulse related artefact” (PRA). Online access to EEG data during fMRI acquisition would allow real time monitoring of the subject’s consciousness state, and possibly neuro-feedback.