EEG & fMRI

EEG-fMRI is a multimodal neuroimaging technique which enables the acquisition of EEG and fMRI data synchronously. The technique is being used worldwide to evaluate normal brain function as well as brain function associated with recognized brain disorders.

Scalp EEG reflects the brain‘s electrical activity, more specifically it represents post-synaptic potentials in the cerebral cortex. fMRI detects haemodynamic changes throughout the brain known as the BOLD effect (Blood Oxygen Level Dependent). EEG-fMRI therefore enables the direct correlation of these two important measures of brain activity.

Brain Products has offered state-of-the-art systems for EEG & fMRI since the year 2000, i.e. providing

• BrainAmp MR series amplifiers – from non magnetic materials – dedicated for use inside the scanner bore.
• offline as well as real-time gradient and pulse artifact correction software (BrainVision Analyzer 2 and BrainVision RecView) for EEG-fMRI artifact correction.
• special “MR conditional” electrode caps – preserving subject safety and image quality

… resulting in hundreds of EEG-fMRI publications using Brain Products Hard- and Software.

Simultaneous acquisition of EEG and fMRI data of good quality is a difficult task. Challenges with regards to subject safety and data quality cannot be underestimated. Careful preparation of the subject in accordance with established safety guidelines for EEG examination in the scanner is mandatory. Due care and attention is needed to avoid potential health risks. One such possible health and safety threat is the precipitation of induced currents dangerous to the subject. Such currents are induced by the MR image forming process if the subject is carelessly hooked up to the EEG acquisition system. Formal risk assessment according to recognized guidelines should be a matter of routine for all researchers working with combined EEG-fMRI protocols.

EEG-fMRI data quality is the other challenge. The MR is a very hostile environment at the best of times but presents particular problems where EEG acquisition is concerned. There are also challenges from the MR point of view. MR images are highly sensitive to contamination by foreign metal objects being placed in the scanner with the subject (even a simple tattoo can seriously distort the images). The EEG recording equipment – when placed in or near a scanner can certainly be described as a ‘foreign metal body’. However, for optimal EEG acquisition (with current available technology) the amplifier really needs to be placed inside the scanner at close proximity to the subject.