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Understanding the Neural Substrates of Neurofeeback Modulations of Visual Attention: Multimodal Brain Imaging and Application to Hemispatial Neglect Syndrome

English title Understanding the Neural Substrates of Neurofeeback Modulations of Visual Attention: Multimodal Brain Imaging and Application to Hemispatial Neglect Syndrome
Applicant Vuilleumier Patrik
Number 192792
Funding scheme Project funding (Div. I-III)
Research institution Dépt des Neurosciences Fondamentales Faculté de Médecine Université de Genève
Institution of higher education University of Geneva - GE
Main discipline Neurophysiology and Brain Research
Start/End 01.06.2020 - 31.05.2024
Approved amount 1'037'365.00
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All Disciplines (2)

Discipline
Neurophysiology and Brain Research
Psychology

Keywords (8)

Neuropsychology; Consciousness; Neurofeedback; EEG; fMRI; Vision; Attention; Neglect syndrome

Lay Summary (French)

Lead
Bases neurales de l'attention visuospatiale et neurofeedback
Lay summary
Les mécanismes d'attention dans le cerveau fonctionnent en modulant l’activité des systèmes sensoriels (par exemple les zones visuelles du cortex occipital) par des signaux de contrôle «descendants» générés dans des réseaux spécifiques du cortex frontal et pariétal. Ces signaux permettent de synchroniser l'activité neuronale pour augmenter ou supprimer les inputs sensoriels. Notamment, des oscillations neuronales dans la bande de fréquence 8-12 Hz (rythme alpha) sont atténuées pour faciliter le traitement sensoriel et amplifiées pour inhiber le traitement sensoriel, mais d'autres rythmes sont également modulés par l'attention (rythmes theta, beta, ou gamma). Ces mécanismes d'attention peuvent être endommagés par des lésions cérébrales focales (par exemple un accident vasculaire cérébral) affectant les réseaux attentionnels et leurs connexions avec les zones sensorielles, provoquant de graves déficits dans la capacité des patients à orienter l'attention dans l'espace (syndrome d’héminégligence).

Cependant, les relations fonctionnelles exactes du rythme alpha avec l’attention, le rôle d’autres fréquence, et leur perturbation par des lésions lors du syndrome de négligence restent peu claires. Dans ce projet, nous enregistrerons simultanément l'EEG et l'IRMf fonctionnelle chez des volontaires sains lors de tâches visuelles attentionnelles de neurofeedback (NFB), leur demandant de réguler soit l'activité alpha en EEG soit l'activité occipitale en IRMf. Ceci nous permettra de (1) mieux déterminer la correspondance différentes fréquences EEG et les changements concomitants de l'activité occipitale en IRMf, et (2) identifier des «biomarqueurs» caractéristiques dans l'EEG reflétant une régulation efficiente des aires occipitales par l'attention. Ces données seront ensuite exploitées pour développer de nouvelles approches d’entrainement de l’attention visuelle chez des patients avec syndrome de négligence.

Direct link to Lay Summary Last update: 22.04.2020

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Associated projects

Number Title Start Funding scheme
180319 Charting emotion components and dynamics in the human brain using virtual reality and cinema 01.09.2018 Sinergia
166704 Harnessing residual unconscious processing with neurofeedback to regulate visual awareness: implications for spatial attention deficits in patients with neglect after stroke 01.05.2016 Project funding (Div. I-III)
166704 Harnessing residual unconscious processing with neurofeedback to regulate visual awareness: implications for spatial attention deficits in patients with neglect after stroke 01.05.2016 Project funding (Div. I-III)

Abstract

Attention mechanisms in the brain work through the modulation of sensory systems (for example visual areas in occipital cortex) by “top-down” control signals generated in specific networks in frontal and parietal cortex, which can synchronize neuronal activity to enhance or suppress sensory inputs. Thus, previous fMRI research has revealed that brain responses to visual stimuli are boosted in occipital areas of the hemisphere opposite to the stimulated visual hemifield when attention is directed to these stimuli, while EEG show changes in the amplitude of rhythmic oscillations recorded over posterior regions of the head, with asymmetries in specific rhythms frequency. In particular, oscillations in the 8-12 Hz (alpha band) are thought to be attenuated to facilitate sensory processing and amplified to inhibit sensory processing, but other rhythms are also modulated by attention (theta band in 4-7 Hz, beta band 13-30 Hz, or gamma >40 Hz) and involve different aspects of synchronization between and within areas across widespread networks. These attention mechanisms can be damaged by focal brain lesions (for example stroke) affecting attentional networks and their connections with visual areas, causing severe impairments in the ability of patients to orient attention in space. In particular, right posterior hemisphere lesions can result in losses in attention and failure to become aware of information in left side of space, a neuropsychological syndrome called “unilateral spatial neglect”. These patients behave as if left space did not exist and suffer from severe handicap in everyday life. Neurophysiological investigations in these patients has revealed that sensory responses to visual are reduced or suppressed in occipital areas, and brain rhythms disturbed in various ways, consistent with impaired modulation of sensory inputs by attention due to a disruption of “top-down” control signals. Recent attempts have used neurofeedback techniques (NFB) allowing real-time measurement of brain activity (with either fMRI or EEG) to train subjects to regulate their attention to left or right sides of space, by providing them with an index of ongoing neural activity in occipital areas. This has also been applied in stroke patients with spatial neglect. Real-time fMRI NFB was used to train people to upregulate activity in occipital cortex on one side, whereas real-time EEG NFB was used to train people to produce asymmetric alpha rhythms over occipital areas, with encouraging but limited benefits in visual attention abilities.However the exact functional relationships of alpha rhythms and respective roles of different oscillation frequencies remain unclear. In this project, we will record EEG and fMRI simultaneously in healthy volunteers during visual attentional NFB tasks where they will learn to regulate either EEG alpha activity or fMRI BOLD activity from occipital areas. First, this will allow us to determine the correspondence of EEG activity across different frequencies in relation to concomitant changes in fMRI activity, and better understand the neurophysiological mechanisms mediating attentional top-down control. Second, these results will allow us to identify characteristic “biomarkers” in EEG reflecting successful attention regulation. These data will then be exploited to develop a new NFB protocol training subjects to up/downregulate such biomarkers based on EEG feedback alone, and examine the subsequent impact on occipital activation with fMRI and behavioral performance attentional tasks. Similar training will be examined in patients with spatial neglect. Altogether, our results will shed new light on neural mechanisms of attention and open new perspectives on NFB protocols to improve rehabilitation of stroke patients.
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