intracranial eeg and human brain mapping

Those studies have all shown a close correspondence between the BOLD signal and the gamma band component of the LFP, in both monkey and cat visual cortex. Most of our current knowledge about the electrophysiological correlates of the BOLD signal come from recent animals studies combining simultaneous haemodynamic and spikes/local field potentials measurements. It remains still unclear which (or which combinations) of these components has the strongest influence on the BOLD signal and this seriously limits the functional interpretation of fMRI signals.

In fact, a number of studies have demonstrated that components of EEG responses often have different spatial and temporal organisation, as well as presenting different reactivity to modulations in a subject's cognitive activity, strongly suggesting that they reflect different neural mechanisms and functions. Indeed, the electrophysiological response evoked by a sensory stimulation, or a motor output always takes the form of an organised collection of event‐related potentials as well as synchronizations and desynchronizations in several frequency bands including theta (4–7 Hz), alpha (8–12 Hz), beta (15–30 Hz) and gamma ranges (>40 Hz). The activity of a small neural population during a time window of the order of seconds is measured by fMRI as a couple of haemodynamic values and by EEG as a composite signal with a complex organization in time and frequency. Though fusing the two techniques is highly desirable, it is no trivial task. INTRODUCTION fMRI-high spatial but poor temporal resolution-and EEG-poor spatial but high temporal resolution-are in principle complementary by nature. Lachaux, Jean‐Philippe Fonlupt, Pierre Kahane, Philippe Minotti, Lorella Hoffmann, Dominique Bertrand, Olivier Baciu, Monica

Relationship between task‐related gamma oscillations and BOLD signal: New insights from combined fMRI and intracranial EEG Relationship between task‐related gamma oscillations and BOLD signal: New insights from combined.

Intracranial eeg and human brain mapping