Fast periodic visual stimulation to highlight the relationship between human intracerebral recordings and scalp electroencephalography

Abstract

Despite being of primary importance for fundamental research and clinical studies, the relationship between local neural population activity and scalp electroencephalography (EEG) in humans remains largely unknown. Here we report simultaneous scalp and intracerebral EEG responses to face stimuli in a unique epileptic patient implanted with 27 intracerebral recording contacts in the right occipitotemporal cortex. The patient was shown images of faces appearing at a frequency of 6 Hz, which elicits neural responses at this exact frequency. Response quantification at this frequency allowed to objectively relate the neural activity measured inside and outside the brain. The patient exhibited typical 6 Hz responses on the scalp at the right occipitotemporal sites. Moreover, there was a clear spatial correspondence between these scalp responses and intracerebral signals in the right lateral inferior occipital gyrus, both in amplitude and in phase. Nevertheless, the signal measured on the scalp and inside the brain at nearby locations showed a 10-fold difference in amplitude due to electrical insulation from the head. To further quantify the relationship between the scalp and intracerebral recordings, we used an approach correlating time-varying signals at the stimulation frequency across scalp and intracerebral channels. This analysis revealed a focused and right-lateralized correspondence between the scalp and intracerebral recordings that were specific to the face stimulation is more broadly distributed in various control situations. These results demonstrate the interest of a frequency tagging approach in characterizing the electrical propagation from brain sources to scalp EEG sensors and in identifying the cortical sources of brain functions from these recordings. K E Y W O R D S face perception, frequency tagging, inferior occipital gyrus, intracerebral electrophysiology, occipitotemporal, SEEG, source imaging, vision † Bruno Rossion and Laurent Koessler contributed equally to this work.

Intracerebral Correlates of Scalp EEG Ictal Discharges Based on Simultaneous Stereo-EEG Recordings

“…We previously validated the EEG volume conduction in the setup of simultaneous EEG-SEEG across in several studies. 16,26,36,37 Future studies, adding relevant clinical variables and data regarding the pattern of propagation of the scalp EEG discharge, could improve the prediction of the EZ localization derived from video-EEG recordings.…”

“…We previously validated the EEG volume conduction in the setup of simultaneous EEG-SEEG across in several studies. 16,26,36,37…”

Transcranial Electrical Stimulation generates electric fields in deep human brain structures

“…In addition to the intracerebral multi-contact electrodes, 27 scalp electrodes were placed according to an adapted 10/20 system [53]. Visual review of the simultaneous EEG-SEEG recordings was done prior to the tACS experiments.…”