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Oulun yliopiston väitöskirjat

INFRA-SLOW FLUCTUATIONS IN SIMULTANEOUS EEG-FMRI, ACTA UNIVERSITATIS OULUENSIS D Medica 1393

ISBN-13:	978-952-62-1387-3
Kieli:	englanti
Kustantaja:	Oulun yliopisto
Oppiaine:	Lääketiede
Painos:	Osajulkaisuväitöskirjan yhteenveto-osa
Painosvuosi:	2016
Sijainti:	Print Tietotalo
Sivumäärä:	84
Tekijät:	KEINÄNEN TUIJA

17.50 €

Brain activity fluctuations occur in multiple spatial and temporal scales. Functional magnetic resonance imaging (fMRI) has shown that infra slow fluctuations (ISF) of blood oxygen leveldependent signal (BOLD) are organized into well-defined areas called resting state networks (RSN). ISFs have also been detected in full-band EEG (fbEEG) data and in recent years, many have combined these two modalities to enable more accurate measurements of brain fluctuations. In simultaneous EEG-fMRI measurements the ISFs of BOLD signal have been found to be correlated with amplitude envelopes of faster electrophysiological data, suggesting the same underlying neuronal dynamics. Also direct correlations have been found in task related studies but not previously in resting state studies. Understanding the relation between EEG and BOLD signal in resting state might prove beneficial in the research of baseline activity fluctuations of the brain. Functional connectivity (FC) of the RSNs has been found to vary in different tasks and in some diseases, but also in resting state in healthy people. Despite numerous studies, no clear cause for these variations has yet been found. To research these open questions we performed simultaneous fbEEG-fMRI studies. The measurements from both modalities were analyzed with independent component analysis to improve the comparability of these results. Correlation analysis revealed that the EEG ISFs correlate with BOLD signal both temporally and spatially. These correlations showed spatiotemporal variability that was related to the strength of RSN functional connectivity. These results indicate that the ISFs of EEG and BOLD reflect a common source of fluctuations. The understanding of the correlations between ISFs in EEG and fMRI BOLD signals gives basic information of brain dynamics and of the variables that affect it. A better understanding of the background of brain activity helps in the development of more effective treatments for various neurological diseases as the knowledge of the mechanisms behind them grows. The ability to measure RSN activity with EEG more accurately can help in the development of new methods for early diagnosis of diseases.

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