Rhythms of the Brain: Dynamic Interactions Between Brain Regions During Episodic Memory Retrieval

Dr. Erika Nyhus, Bowdoin College, Department of Psychology, and Program in Neuroscience

Evidence from fMRI has consistently located a widespread network of frontal, parietal, and temporal lobe regions that are important for the cognitive control of episodic memory retrieval. But it is unclear how these distributed regions of the brain dynamically interact to support control of episodic retrieval. It has been proposed that neural oscillations provide the means by which brain areas interact to perform cognitive tasks. Specifically, theta (4-8 Hz) and beta (17-20 Hz) oscillations may provide a mechanism of top-down control in episodic memory retrieval. In this talk I will present a series of EEG and simultaneous EEG and fMRI studies examining whether theta and beta oscillations are the means by which frontal and posterior brain regions coordinate activity for the control of episodic memory retrieval. Frontal theta power was greater for old than new words and parietal beta power was greater for new than old words and these memory effects were enhanced under conditions requiring more cognitive control. Combined EEG/fMRI results showed that beta power was correlated with the fMRI BOLD response in right prefrontal cortex. These results suggest that theta and beta oscillations are important for coordinating activity in a fronto-parietal control network during episodic memory retrieval.