Brain oscillatory activity during motor imagery in electroencephalography functional magnetic resonance imaging coregistration

Introduction: Recording electroencephalogram data (EEG) during functional magnetic resonance imaging (fMRI) identifies brain activity in motor areas and provides information on the source of the event generator. Objectives: The purpose of the present work was to investigate the correlation between topographical changes in brain oscillatory activity and the blood oxygenation level dependent (BOLD) signal during a motor imagery (MI) task using EEG-fMRI coregistration. Methods: EEG was recorded in 7 healthy subjects inside a 1.5T magnetic resonance scanner during the imagination of the kinesthetic experience of movement. A Fast Fourier Transform was applied to EEG signal in the rest and active conditions. We used the event-related- synchronization/desynchronization (ERS/ERD) approach to characterize where the imagination of movement produces a decrease in alpha and beta powers. Results: The mean alpha map showed ERD localized over the contralateral sensory motor area (SM1c) and a light desynchronization in the ipsilateral sensory motor area (SM1i); whereas the mean beta map showed ERD over the supplementary motor area (SMA). fMRI showed significant activation in SMA, SM1c, and SM1i. In the contralateral side we observed a negative correlation between ERD and BOLD signals, whereas in the ipsilateral one a positive correlation. Conclusions: Using combined EEG-fMRI signals we obtained useful new information on the description of the changes in oscillatory activity in alpha and beta bands during MI and on the investigation of the sites of BOLD activity as possible sources in generating these rhythms. By correlating BOLD and ERS/ERD we may identify more accurately which regions contribute to changes of the electrical response.