This study investigates the relationship between the alpha rhythm in EEG and MRI signal changes using simultaneous EEG and fMRI. The alpha rhythm, present in the 8–12 Hz range, is associated with cortical inactivity and is most prominent when a subject is awake with eyes closed. The study used simultaneous EEG and fMRI to map brain regions whose MRI signal changed with alpha rhythm modulation. Eleven subjects were scanned while resting with eyes closed, and the results showed that increased alpha power was correlated with decreased MRI signal in occipital, superior temporal, inferior frontal, and cingulate cortex, and with increased signal in the thalamus and insula. These findings align with animal studies and suggest the alpha rhythm as an indicator of cortical inactivity, possibly generated by the thalamus. The study also highlights the importance of resting state in fMRI studies, as alpha rhythm changes may account for some of the BOLD changes observed in baseline measures. The results are consistent with previous findings that the thalamus may play a role in generating the alpha rhythm. The study used a technique called simultaneous imaging for tomographic electrophysiology (SITE) to combine the high spatial resolution of fMRI with the high temporal resolution of EEG. This method allowed for the localization of potential generator regions of the alpha rhythm during eyes closed rest. The study found that alpha power correlated negatively with MRI signal in occipital, superior temporal, and inferior frontal regions, and positively with MRI signal in the thalamus and insula. These findings suggest that the alpha rhythm is associated with cortical inactivity and that the thalamus may play a role in generating this state. The study also found that drowsiness may influence alpha rhythm modulation, but the results were consistent across subjects and scans. The findings have implications for interpreting resting state brain activity in fMRI studies and for understanding the role of the thalamus in generating the alpha rhythm.This study investigates the relationship between the alpha rhythm in EEG and MRI signal changes using simultaneous EEG and fMRI. The alpha rhythm, present in the 8–12 Hz range, is associated with cortical inactivity and is most prominent when a subject is awake with eyes closed. The study used simultaneous EEG and fMRI to map brain regions whose MRI signal changed with alpha rhythm modulation. Eleven subjects were scanned while resting with eyes closed, and the results showed that increased alpha power was correlated with decreased MRI signal in occipital, superior temporal, inferior frontal, and cingulate cortex, and with increased signal in the thalamus and insula. These findings align with animal studies and suggest the alpha rhythm as an indicator of cortical inactivity, possibly generated by the thalamus. The study also highlights the importance of resting state in fMRI studies, as alpha rhythm changes may account for some of the BOLD changes observed in baseline measures. The results are consistent with previous findings that the thalamus may play a role in generating the alpha rhythm. The study used a technique called simultaneous imaging for tomographic electrophysiology (SITE) to combine the high spatial resolution of fMRI with the high temporal resolution of EEG. This method allowed for the localization of potential generator regions of the alpha rhythm during eyes closed rest. The study found that alpha power correlated negatively with MRI signal in occipital, superior temporal, and inferior frontal regions, and positively with MRI signal in the thalamus and insula. These findings suggest that the alpha rhythm is associated with cortical inactivity and that the thalamus may play a role in generating this state. The study also found that drowsiness may influence alpha rhythm modulation, but the results were consistent across subjects and scans. The findings have implications for interpreting resting state brain activity in fMRI studies and for understanding the role of the thalamus in generating the alpha rhythm.