Task- and EEG-correlated analyses of BOLD MRI responses to eyes opening and closing.

Variations of a subject's vigilance may pose a severe confound during functional brain mapping. Here, we focused on BOLD MRI responses to eyes opening and closing in complete darkness and the associated changes in the EEG's alpha frequency band (Berger's effect) as a possible approach to this problem. In awake subjects, BOLD MRI activation patterns were positively correlated to eyes opening and negatively to alpha power. In contrast, activation patterns of subjects with diminished wakefulness as determined by alpha band analysis were negatively correlated to eyes opening. We conclude that a control of the subjects' state of wakefulness must be of prime concern for functional MRI, especially for paradigms which allow for a free shift of vigilance.