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Society for Neuroscience
New Orleans, Louisiana
November 8-12, 2002
Julie Onton & Scott Makeig ,
Institute for Neural Computation, UCSD & The Salk Institute, La Jolla CA
Frontal and posterior EEG dynamics during working memory
Here, we correlate EEG dynamics with subject behavior during a working memory task. Subjects were presented with sequences of 8 letters, 3-7 of which (colored black) were to be memorized, while the rest (colored green) were to be ignored. A probe letter was presented 2.2-4.2 sec after the offset of the last letter. The subject pressed one of two buttons to indicate whether the probe letter had been in the memorized letter set. EEG channel data were decomposed using Independent Component Analysis (ICA) to find activations compatible with synchronized activity in one or rarely two bilaterally symmetric cortical patches. In midfrontal components, power in the (4-8 Hz) theta band increased with each letter to be memorized and during the maintenance period was lowest for 3 letter sets and highest for 7 letter sets, indicating theta power indexed memory load. Power at 13 Hz in these same components was higher during letters to be memorized than those to be ignored. However no consistent load effect was observed at 13 Hz. Posterior components showed an opposite pattern; there, power in alpha and beta bands increased during ignored letters and decreased during memorized. The results show distinct patterns of EEG dynamics associated with short term memory load and attention to visual stimuli.