Studying
Cognitive Activity at several LEvels with Simultaneous depth and surface
recordings
|
Grant COFUND-FLAGERA II-SCALES |
HOME | OBJECTIVES | RESULTS | TEAM |
SUMMARY
Intracerebral EEG (stereotaxic
EEG, SEEG) is an invasive measure of brain activity performed during the
presurgical evaluation of epilepsy, involving up to 250 distinct channels
that record directly from brain structures, at the mesoscopic scale (a few
millimetres). SEEG is performed on purely diagnostic/therapeutic motivations;
collaterally, it provides a unique opportunity for investigating cognitive
brain networks in humans across multiple frequencies with an exquisite
spatial specificity, and matchless signal-to-noise ratio. Recently, the
microscopic scale has been obtained thanks to microcontacts added to the SEEG
probes. The analysis of such SEEG recordings at the meso- and micro- scales
has fuelled advances in cognitive neuroscience, notably in the fields of
memory and language. Still, SEEG provides only a partial view of brain
activity due to its patient-specific limited spatial sampling. Noninvasive
methods such as EEG and MEG remain the only way to obtain a macroscopic view
of brain activity at its natural temporal scale (i.e., at the millisecond level)
with a large spatial field of view.
Recent research has started to bridge
the gap between the macroscopic and mesoscopic scales in humans, by recording
simultaneously invasive (SEEG) and non-invasive (EEG, MEG) neurophysiological
signals. Such recordings could be used jointly for characterizing brain
networks, surpassing the simple addition of modalities. Crucially, simultaneous
recordings provide a view of the exact same brain activity at the different
scales, and allows applying powerful single-trial analysis which would not be
available on recordings performed separately across scales.
Our goal is to
better define the spatio-temporal signature of the brain networks involved in
simple cognitive tasks using simultaneous surface and depth recordings. Depth
recordings will be instrumental in guiding the exploration of functional task
networks, either by allowing analyses at the level of single trials, or by
providing high resolution seeds for connectivity measures. In one centre, we
will explore the possibility of adding micro recordings, thus collecting for
the first time simultaneously the three scales: micro-, meso- and macro-. Part
of the project will be dedicated to methodological (signal processing)
advances. The other part will focus on applying this unique technique to
unravel multi-scale cognitive networks.
A consortium composed of Institut
de Neuroscience des Systèmes - Aix-Marseille Université (C. Bénar), Physics
Department of the Bucharest University (A Barborica), and Hôpitaux
Universitaires de Genève (S. Vulliemoz) has been established in order to achieve
these goals. The partners involved have extensive
experience on non-invasive electrophysiology (EEG, MEG), on (intracerebral)
SEEG recordings, as well as on their simultaneous recording. The
consortium
includes experts on signal processing for brain neurophysiological data, notably
in the service of cognitive questions. The resulting datasets will be made
available to the scientific community. Such reference datasets should be
particularly useful for i) optimizing signal processing methods on surface
data by providing a "ground truth" (SEEG) and ii) developing computational
models of brain activity that incorporate knowledge from activity at all
scales.