Coregistration of fMRI BOLD clusters and EEG source model in the individual MR image.
The BrainVoyager program has a bi-directional interactive link with BESA. Files with digitized sensor positions and fiducials are created in BESA and optimized in BrainVoyager to match with the 3D rendered surface mesh. For each subject/session this coregistration of the sensor/surface point file with the individual MRI has to be done once only.With one click, the source model in BESA can be sent to BrainVoyager and visualized in the volume or 3D surface displays. In the SEF experiment with right tactile stimulation (Hoechstetter et al. 2000), for example, the red dipole localized near area 3B in the central sulcus (SI) while later activity was found in secondary somatosensory cortex bilaterally (blue dipole: contralateral SII). The dipoles are localized close to the fMRI BOLD clusters.
Conversely, a multiple dipole model can be created rapidly by right click onto fMRI BOLD clusters. The center coordinates of the cluster are transmitted to BESA and a source is automatically created at the corresponding location in the BESA head model. Dipole orientation is fitted automatically to the marked data epoch. With one more click in BESA on the BrainVoyager button, the seeded dipole can be sent back for control.
This example of MEG, MRI, and fMRI is provided on our demonstration CD.