Simultaneous EEG-fMRI during a Working Memory Task: Modulations in Low and High Frequency Bands
Open Access
- 22 April 2010
- journal article
- research article
- Published by Public Library of Science (PLoS) in PLOS ONE
- Vol. 5 (4), e10298
- https://doi.org/10.1371/journal.pone.0010298
Abstract
EEG studies of working memory (WM) have demonstrated load dependent frequency band modulations. FMRI studies have localized load modulated activity to the dorsolateral prefrontal cortex (DLPFC), medial prefrontal cortex (MPFC), and posterior parietal cortex (PPC). Recently, an EEG-fMRI study found that low frequency band (theta and alpha) activity negatively correlated with the BOLD signal during the retention phase of a WM task. However, the coupling of higher (beta and gamma) frequencies with the BOLD signal during WM is unknown. In 16 healthy adult subjects, we first investigated EEG-BOLD signal correlations for theta (5–7 Hz), alpha1 (8–10), alpha2 (10–12 Hz), beta1 (13–20), beta2 (20–30 Hz), and gamma (30–40 Hz) during the retention period of a WM task with set size 2 and 5. Secondly, we investigated whether load sensitive brain regions are characterised by effects that relate frequency bands to BOLD signals effects. We found negative theta-BOLD signal correlations in the MPFC, PPC, and cingulate cortex (ACC and PCC). For alpha1 positive correlations with the BOLD signal were found in ACC, MPFC, and PCC; negative correlations were observed in DLPFC, PPC, and inferior frontal gyrus (IFG). Negative alpha2-BOLD signal correlations were observed in parieto-occipital regions. Beta1-BOLD signal correlations were positive in ACC and negative in precentral and superior temporal gyrus. Beta2 and gamma showed only positive correlations with BOLD, e.g., in DLPFC, MPFC (gamma) and IFG (beta2/gamma). The load analysis revealed that theta and—with one exception—beta and gamma demonstrated exclusively positive load effects, while alpha1 showed only negative effects. We conclude that the directions of EEG-BOLD signal correlations vary across brain regions and EEG frequency bands. In addition, some brain regions show both load sensitive BOLD and frequency band effects. Our data indicate that lower as well as higher frequency brain oscillations are linked to neurovascular processes during WM.This publication has 95 references indexed in Scilit:
- A common functional brain network for autobiographical, episodic, and semantic memory retrievalNeuroImage, 2010
- Trial-by-trial coupling between EEG and BOLD identifies networks related to alpha and theta EEG power increases during working memory maintenanceNeuroImage, 2009
- Performance- and stimulus-dependent oscillations in monkey prefrontal cortex during short-term memoryFrontiers in Integrative Neuroscience, 2009
- EEG alpha distinguishes between cuneal and precuneal activation in working memoryNeuroImage, 2008
- Effects of Working Memory Load on Oscillatory Power in Human Intracranial EEGCerebral Cortex, 2007
- Individual differences in EEG theta and alpha dynamics during working memory correlate with fMRI responses across subjectsClinical Neurophysiology, 2007
- Electrophysiological signatures of resting state networks in the human brainProceedings of the National Academy of Sciences of the United States of America, 2007
- Parieto‐occipital sources account for the increase in alpha activity with working memory loadHuman Brain Mapping, 2007
- Impairments in frontal cortical γ synchrony and cognitive control in schizophreniaProceedings of the National Academy of Sciences of the United States of America, 2006
- Distinct prefrontal cortex activity associated with item memory and source memory for visual shapesCognitive Brain Research, 2003