Dynamics of oscillatory networks in human: from intracranial to eeg-meg scalp recordings
Mental processes are known to activate distributed networks of specialized brain structures. Neuroimaging techniques provide more and more precise pictures of these networks in different sensory and cognitive situations but the neural mechanisms underlying the network dynamics of interactions have been much less explored. As an influential hypothesis, the co-operation within or between brain areas involved in sensory and cognitive processes could be based on the dynamic synchronization of the underlying neural populations in an oscillatory mode (in the beta and gamma ranges). This hypothesis has been supported at different levels, with unit and local field potential recordings in animal studies, and at intermediate (intracranial EEG) and more macroscopic levels (scalp EEG/MEG) in humans. Stimulus induced oscillations can have different temporal dynamics, and can be modulated by bottom-up or top-down processes related to perception, attention or memory. They can be restricted to low-level sensory areas (local synchronization) or distributed over more extended networks for higher-level processing (long-distance interactions). Multiple foci of beta and gamma activities have been observed in the visual and auditory modalities, and were found to be modulated by stimulus and behavioral tasks. The comparison of these different levels of recordings will be discussed.