RESUMO
OBJECTIVES: Synchronous electroencephalogram (EEG) and functional magnetic resonance imaging (fMRI) has been used to explore sleep stage dependent functional brain networks. Despite a growing number of sleep studies using EEG-fMRI, few studies have conducted network analysis on whole night sleep due to difficulty in data acquisition, artifacts, and sleep management within the MRI scanner. METHODS: In order to perform network analysis for whole night sleep, we proposed experimental procedures and data processing techniques for EEG-fMRI. We acquired 6–7 hours of EEG-fMRI data per participant and conducted signal processing to reduce artifacts in both EEG and fMRI. We then generated a functional brain atlas with 68 brain regions using independent component analysis of sleep fMRI data. Using this functional atlas, we constructed sleep level dependent functional brain networks. RESULTS: When we evaluated functional connectivity distribution, sleep showed significantly reduced functional connectivity for the whole brain compared to that during wakefulness. REM sleep showed statistically different connectivity patterns compared to non-REM sleep in sleep-related subcortical brain circuits. CONCLUSION: This study suggests the feasibility of exploring functional brain networks using sleep EEG-fMRI for whole night sleep via appropriate experimental procedures and signal processing techniques for fMRI and EEG.
Assuntos
Artefatos , Encéfalo , Eletroencefalografia , Imageamento por Ressonância Magnética , Fases do Sono , Sono REM , VigíliaRESUMO
Los recientes avances en las técnicas de neuroimagen han contribuido en la comprensión de la dinámica funcional del cerebro. Especialmente, los estudios simultáneos de EEG-fMRI han aportado valiosa información estudiando dicha dinámica desde dos frentes, la actividad eléctrica y la hemodinámica. En el siguiente artículo se realiza una revisión de la técnica, el hardware requerido, las formas de análisis, sus principales inconvenientes y los logros obtenidos en el estudio de la epilepsia y el dolor.
Recent advances in neuroimaging techniques have contributed in functional dynamics comprehension of the brain. Specially, the simultaneous studies of EEG-fMRI have provided valuable information, by studying that brain dynamics from two points of view: bioelectricity and hemodynamics. In this paper, we review the technique, the required hardware and the methods of analysis. The main drawbacks and achievements obtained in the study of epilepsy and pain are presented, as well.
RESUMO
Simultaneous measurements of EEG-functional magnetic resonance imaging (fMRI) combine the high temporal resolution of EEG with the distinctive spatial resolution of fMRI. The purpose of this EEG-fMRI study was to search for hemodynamic responses (blood oxygen level-dependent - BOLD responses) associated with interictal activity in a case of right mesial temporal lobe epilepsy before and after a successful selective amygdalohippocampectomy. Therefore, the study found the epileptogenic source by this noninvasive imaging technique and compared the results after removing the atrophied hippocampus. Additionally, the present study investigated the effectiveness of two different ways of localizing epileptiform spike sources, i.e., BOLD contrast and independent component analysis dipole model, by comparing their respective outcomes to the resected epileptogenic region. Our findings suggested a right hippocampus induction of the large interictal activity in the left hemisphere. Although almost a quarter of the dipoles were found near the right hippocampus region, dipole modeling resulted in a widespread distribution, making EEG analysis too weak to precisely determine by itself the source localization even by a sophisticated method of analysis such as independent component analysis. On the other hand, the combined EEG-fMRI technique made it possible to highlight the epileptogenic foci quite efficiently.