Studying Cognitive Activity at several LEvels with Simultaneous depth and surface recordings

Grant COFUND-FLAGERA II-SCALES
15/2018

   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.