Verlag des Forschungszentrums Jülich
JUEL-3808
From Experiment 1 we identified four different CMV generators (auditory cortex, sensori-
motor cortex, inferior prefrontal cortex, posterior inferior parietal area) and observed
prirning of the auditory cortex as part of the early CMV complex and the priming of the
sensorimotor cortex as part of the late CMV complex. These results were confirmed by
Experiment 2, where the full head coverage also revealed two additional areas, the
supplementary motor area and the posterior cingulate cortex, which were dramatically
reduced when identical runs were repeated. The SMA activity has been notoriously
difficult to identify non-invasively from electrophysiological data, especially from MEG,
so our success in identifying them clearly and showing how they change with repetition can
be considered as the highlight of our project.
Dammers, Jürgen
Localisation and time courses of CMV generators from, MFT analysis of average MEG signals
229 S., 2000
The research presented here is divided into two parts. The first part addresses questions
relating to the localisation capability of magnetoencephalography (MEG), with emphasise
on testing the accuracy of typical MEG systems before any source reconstruction is
applied. The second and main part is concemed with localisation and time courses of
neuronal generators contributing to both the slow and fast neuromagnetic field changes
associated with the contingent negative variation (CNV) in the normal human brain. We
use multi-channel and full head MEG systems to study the magnetic counterpart of the
CNV, the contingent magnetic variation (CMV). MEG analysis of such near DC-like
signals requires advanced source reconstruction that is able to identify widely distributed as
well as focal sources which often fire simultaneously from cortical as well as from deeper
brain structures. We use magnetic field tomography (MFT) to extract time courses of
regional brain activity. Results are presented from a multi-subject CMV study performed
using the BTi MAGNES n system (Experiment 1) and a single subject experiment, using
the CTF whole cortex system (Experiment 2).
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