Do specific EEG frequencies indicate different processes during mental calculation?

EEG recordings during mental calculation and a control task (with presentat ion of stimuli with similar physical characteristics to the arithmetic symb ols) were obtained in 10 subjects. Narrow band analyses of the EEG and dist ributed sources for each EEG frequency were calculated using variable resol ution electromagnetic tomography. Significant differences between the sourc es for arithmetic and control tasks were observed at 3.9 Hz within Broca's and left parietotemporal cortices, suggesting that this frequency may be re lated with the production of internal speech, storage and rehearsal of verb al working memory. Differences at 5.46 Hz within the right dorsolateral pre frontal cortex were considered to be associated to sustained attention. The decrease at 12.46 Hz within the left parietal cortex was interpreted as a sign of retrieval of arithmetic facts from long term memory. (C) 1999 Elsev ier Science Ireland Ltd. All rights reserved.