Individual differences in EEG theta and alpha dynamics during working memory correlate with fMRI responses across subjects.
OBJECTIVE
Theta and alpha range EEG oscillations are commonly induced in cognitive tasks, but their possible relationship to the BOLD signal of fMRI is not well understood, and individual variability is high. We explored individual differences in EEG reactivity to determine whether it is positively or negatively correlated with BOLD across subjects.


METHODS
A Sternberg working memory task with 2, 4, or 6 digits was administered to 18 subjects in separate fMRI and EEG sessions. Memory load-dependent theta and alpha reactivity was quantified and used as a regressor to reveal brain areas exhibiting EEG-fMRI correlation across subjects.


RESULTS
Theta increases localized to medial prefrontal cortex, and correlated negatively with BOLD in that region and in other "default mode" areas. Alpha modulation localized to parietal-occipital midline cortex and also correlated negatively with BOLD.


CONCLUSIONS
Individual tendencies to exhibit memory load-dependent oscillations are associated with negative BOLD responses in certain brain regions.


CONCLUSIONS
Positive BOLD responses and increased EEG oscillations do not necessarily arise in the same regions. Negative BOLD responses may also relate to cognitive activity, as traditionally indexed by increased EEG power in the theta band.
Meltzer
Jed A
JA
Yale University, Interdepartmental Neuroscience Program, PO Box 208043, TAC N134, New Haven, CT 06520-8043, USA. jed.meltzer@aya.yale.edu
Negishi
Michiro
M
Mayes
Linda C
LC
Constable
R Todd
RT
D000328:Adult; D000513:Alpha Rhythm; D000704:Analysis of Variance; D001921:Brain / Q000098:blood supply* / Q000502:physiology*; D001931:Brain Mapping; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D007206:Individuality; D008279:Magnetic Resonance Imaging; D008297:Male; D008570:Memory, Short-Term / Q000502:physiology*; D009483:Neuropsychological Tests; D017711:Nonlinear Dynamics; D010100:Oxygen / Q000097:blood; D011930:Reaction Time; D013057:Spectrum Analysis; D013223:Statistics as Topic; D013826:Theta Rhythm
D010100:Oxygen