Simultaneous EEG and fMRI in a visual selective attention task

EEG (ERP) and fMRI are two brain imaging modalities with partially
complementary benefits, i.e. high temporal resolution for EEG and high spatial
resolution for fMRI. Simultaneous recording of EEG and fMRI has several
interests, among others the possibility to obtain ERP data and functional
images in the exact same conditions and environment. Recently, several groups
have shown that it is possible to obtain ERPs in the MRI scanner, similar to
the ERPs obtained outside of the scanner. In our lab, a specific experimental
paradigm, the grating task, has been used for several years to assess visual
selective attention from EEG recordings. The analysis of the EEG data results
in a series of components, varying in amplitude, polarity, latency and scalp
position. We have adapted the grating task to be suitable for simultaneous
EEG-fMRI. In the EEG data obtained during this adapted task, some of the
components associated with visual selective attention are observed. So far, no
simultaneous EEG-fMRI recordings have been performed during this task.

In this project, we will examine whether the simultaneous recording of ERPs and
fMRI during the adapted grating task results in data of sufficient quality.
More specifically, we would like to know 1) whether the components normally
observed in the EEG data can also be retrieved from EEG recordings in the MRI
scanner. Furthermore, we would like to know 2) whether the fMRI data are of
sufficient quality to find the generators of the components associated with
visual selective attention.

Maximal twenty-five healthy volunteers will be recruited. Participants will
undergo a maximum of 2 sessions on two different testing days. In the first
session, 64-channel EEG data are recorded while the subject performs the
adapted grating task. These data will be analyzed on the occurance of the
expected components. Subjects with components of the expected polarity are
selected for the second session; twelve subjects will be included in total. EEG
data will also be analyzed with source localisation programs, which will serve
as a reference for later fMRI source localisations. In the second session, a
31-channel reference EEG will be recorded using a MRI-compatible EEG cap.
Subsequently, combined EEG-fMRI will be performed during the adapted grating
task.

The burden for participants is low: the two methods used (EEG and fMRI) are
generally experienced as a light burden. Invasive techniques will not be used.
The total duration of participation is maximal 4,5 hours, during two sessions
spread over maximal 8 weeks. A MRI-compatible EEG system will be used, which
has been approved by the METC UMC Utrecht (protocol number 04/276). In previous
experiments, no adverse effects have been encountered with this system.
Therefore, the risks for subjects are expected to be very low.