В ближайшее время в Научно-образовательном МЭГ-центре МГППУ-ВШЭ состоится очередной семинар
Адрес: Шелепихинская набережная, 2А, с.2
19.02.2019 прошел семинар
EEG and MEG studies of brain mechanisms of cognitive control using time-frequency analysis
Докладчик – Борис Владимирович Чернышев, доцент, кандидат биологических наук, руководитель МЭГ-центра
Cognitive control is a set of processes that are responsible for flexible goal-directed behaviour. It can be viewed as an interplay between two constituent aspects: maintenance of task-specific processes related to attention, and non-specific regulation of motor threshold, both of them having strong influence on response accuracy and response time. Failures in each system lead to different types of errors, associated either with attentional lapses and uncertainty, or with dysfunction of the motor threshold. Performance monitoring and outcome prediction are also basic processes involved in cognitive control.
We did a series of EEG experiments during the auditory condensation task, which is highly demanding for sustained attention. We analyzed EEG oscillations in theta, alpha and beta bands.
In the first study, we used data-driven approach to capture basic brain networks involved in cognitive control. The results of this study indicate that adaptive adjustments after errors are implemented by the frontal-medial network of task performance monitoring, the parietal attentional network and the sensorimotor network.
In the second study, we aimed to find out if response time could be a valid approximation distinguishing trials with high and low levels of attention and decision uncertainty. We focused on response-related and feedback-related modulations, since “internal” response-related outcome detection is likely in conditions of attention and certainly, while “external” feedback-related outcome detection is more likely in conditions of inattention and uncertainty. The analysis of theta, alpha and beta oscillations confirmed our hypotheses.
In the third study, we used a task that involved complex stimulus-to-response mapping that was acquired by participants in the course of "trial-and-error" learning. We analyzed correct and erroneous responses at the early stage of learning, as well as the correct responses at a later stage of learning characterized by a high level of task performance. In contrast to studies using EEG, this MEG study revealed a distributed cortical network of theta oscillation sources that extended far beyond midfrontal areas. The data obtained confirmed the existence of two components of the prediction error: the early component of the response to the feedback signal corresponded to the component of the “unsigned” prediction error, while the late component of the response to the feedback signal reflected the “unsigned” prediction error. This study demonstrated the applicability of MEG for studying theta oscillations as a correlate of cognitive control processes.
13.02.2019 прошел семинар
«Gamma oscillations and excitation/inhibition balance in the brain»
Докладчик - Елена Владимировна Орехова, доктор психологии, ведущий научный сотрудник МЭГ-центра, ведущий научный сотрудник Гётеборгского университета
Gamma frequency oscillations (30 to 100 Hz) are ubiquitous in the brain and involved in multiple cognitive and perceptual processes. While the role of gamma oscillations as a basic mechanism of information processing is still debated, researchers generally agree that these oscillations may provide useful information on excitation/inhibition interactions in the brain. This has important clinical implications, since gamma-range activity can be noninvasively recorded by magnetoencephalography (MEG) and can potentially help to assess the excitation/inhibition balance in brain disorders. It is however still unclear what parameters of the gamma waves are most relevant. In a series of studies we investigated how visual gamma oscillations are modulated by the strength of excitatory drive and how these modulations are related to behavioral indexes of neural inhibition. Our results suggest that stimulation-related changes in gamma oscillations, rather then absolute vales of their frequency or amplitude, give important information about the capacity of inhibitory networks to regulate the excitation/inhibition balance in healthy and diseased brain. In this presentation I will shortly tell about phenomenon of gamma oscillations and then present findings of our group.
05.02.2019 прошел семинар
«Epilepsy surgery driven by innovative biomarkers and cognitive assessment of specific brain functions»
by Tommaso Fedele, Assistant professor, Institute of Cognitive Neuroscience Higher School of Economics - National Research University
Nowadays, about one third of epilepsy patients are refractory to pharmacological treatment, becoming candidate for surgical intervention. Surgical planning faces two major problems: 1) the correct identification the epileptogenic zone, which is frequently adjacent to but often not identical with the epileptogenic lesion, and its differentiation from functional brain tissue, which should be preserved during surgery; 2) the evaluation of the post-operative cognitive deficit, which depends on the residual functionality of the resected area. Beside medical and technological advances in the field of epilepsy surgery, reliable biomarkers guiding optimal resection of the epileptogenic zone are still lacking. Moreover, the neurophysiological evaluation of residual functionality in the epileptic brain is still poorly investigated.
In the past years I contributed to validate high frequency oscillations (HFO) in the intracranial EEG as an innovative biomarker for the delineation of the epileptogenic zone. While HFO are detected in the macro-scale EEG, known as local field potential, we combined routine clinical recordings with multi-unit neuronal activity and evaluated the relation between HFO and single unit activity in human tissue in vivo. In order to control for potential post-surgical cognitive deficit, we investigated the neurophysiological response during a set of cognitive paradigms. In this seminar I will present published results and ongoing analysis on intracranial EEG recording which are of interest to the clinical, neurophysiological an cognitive domain.
I will also present the project framework I plan to establish here in Moscow. We aim to perform clinical and cognitive assessment of pharmaco-resistant epilepsy patients designated for intracranial encephalography (iEEG) to guide surgical planning. The patients participating to our study will be first recorded in the magnetoencephalography (MEG) before receiving the stereo-iEEG implantation, then a similar set of recording will be performed after implantation in the intensive monitoring unit in the clinical institute. The output of our analysis will support the clinical evaluation and minimize post-operative cognitive deficit on single patient basis.