Spatiotemporal structure of intracranial electric fields induced by transcranial electric stimulation in humans and nonhuman primates

Transcranial electric stimulation (TES) is an emerging technique, developed to non-invasively modulate brain function. However, the spatiotemporal distribution of the intracranial electric fields induced by TES remains poorly understood. In particular, it is unclear how much current actually reaches the brain, and how it distributes across the brain. Lack of this basic information precludes a firm mechanistic understanding of TES effects. In this study we directly measure the spatial and temporal characteristics of the electric field generated by TES using stereotactic EEG (s-EEG) electrode arrays implanted in cebus monkeys and surgical epilepsy patients. We found a small frequency dependent decrease (10%) in magnitudes of TES induced potentials and negligible phase shifts over space. Electric field strengths were strongest in superficial brain regions with maximum values of about 0.5 mV/mm. Our results provide crucial information of the underlying biophysics in TES applications in humans and the optimization and design of TES stimulation protocols. In addition, our findings have broad implications concerning electric field propagation in non-invasive recording techniques such as EEG/MEG

The neuronal mechanisms that underlie auditory and visual perception in the human brain studied by direct electrical recordings and stimulation

We are who we are through our brains. In the armamentarium of scientists who study the human brain, intracranial EEG holds a special place. Intracranial EEG refers to recordings of the brain's activity from within the skull, in immediate contact with the brain's tissue. The technique is necessary in the management of a handful of medical conditions. Thanks to the ingenuity of physicians and the selflessness of patients, it can also reveal how neuronal activity underlies normal cerebral functions. In this collection of articles, I highlight the power and versatility of intracranial EEG to reveal the neuronal underpinnings of cerebral function in humans

Preprocessed EEG data

AbstractThis dataset consists of the preprocessed EEG data from 15 participants in a speech perception experiment using virtual characters and synthetic speech. The EEG data for all participants are contained in large MATLAB data files. A text file briefly describes the content of each MATLAB data file

Input and output data from the behavioral experiment

AbstractThis dataset consists of the input and output data (stored as comma-separated values files) from a custom-designed behavioral experiment on the perception of artificial but naturalistic audiovisual speech. 24 participants attended the experiment. Each participant ran 2 blocks. Consequently, there are 2 input .csv files and 2 output .csv files per participant. Additionally, a MATLAB script to upload the data and make them available for further analysis is provided

Electric source imaging for presurgical epilepsy evaluation: current status and future prospects

Introduction: Electric source imaging (ESI) refers to the estimation of the cerebral sources of electric signals recorded at the head surface using electroencephalography (EEG). Thanks to the availability of EEG systems with high numbers of electrodes and to progress in software to analyze the signals they collect, ESI can be applied to epilepsy-related pathological EEG signals like interictal spikes and seizures.Areas covered: In this narrative review, we discuss selected original research articles on the use of ESI in epilepsy patients considered for surgery. Epilepsy-related activity can be localized accurately using ESI, as established by comparison to the gold standards of intracranial EEG and seizure control following epilepsy surgery. The information brought by ESI complements successfully that of other techniques like magnetic resonance imaging and positron-emission tomography, and is clinically relevant to patient management.Expert opinion: EEG is a readily available technique to measure brain activity in real time. Given its accuracy and usefulness, ESI should become part of the routine practice of clinical neurophysiology laboratories and epilepsy centers in the presurgical management of epilepsy patients

Electroencephalography, magnetoencephalography and source localization: their value in epilepsy

Source localization of cerebral activity using electroencephalography (EEG) or magnetoencephalography (MEG) can reveal noninvasively the generators of the abnormal signals recorded in epilepsy, such as interictal epileptic discharges (IEDs) and seizures. Here, we review recent progress showcasing the usefulness of these techniques in treating patients with drug-resistant epilepsy

The phase of cortical oscillations determines the perceptual fate of visual cues in naturalistic audiovisual speech

When we see our interlocutor, our brain seamlessly extracts visual cues from their face and processes them along with the sound of their voice, making speech an intrinsically multimodal signal. Visual cues are especially important in noisy environments, when the auditory signal is less reliable. Neuronal oscillations might be involved in the cortical processing of audiovisual speech by selecting which sensory channel contributes more to perception. To test this, we designed computer-generated naturalistic audiovisual speech stimuli where one mismatched phoneme-viseme pair in a key word of sentences created bistable perception. Neurophysiological recordings (high-density scalp and intracranial electroencephalography) revealed that the precise phase angle of theta-band oscillations in posterior temporal and occipital cortex of the right hemisphere was crucial to select whether the auditory or the visual speech cue drove perception. We demonstrate that the phase of cortical oscillations acts as an instrument for sensory selection in audiovisual speech processing