Interpreting EEG functional brain activity

A critical issue in the presurgical evaluation of brain operations is mapping regions that control speech and language functions. The goal is to preserve these regions during surgery. Mapping done by electrically stimulating the cortex subdurally with implanted electrodes is highly effective, but introduces a high risk for cortical tissue injury. Mapping the brain with non-invasive techniques, such as EEG recordings, is possible. The object of our study is to show that the results produced could be effective and useful, without any risk to the patient. EEG data was collected using electrical source-imaging, with up to 256 electrodes (ESI-256 system). The EEG of each subject was recorded during an auditory/comprehension test using 41 key locations of the possible 256 according to the modified combinatorial nomenclature (MCN). The representations obtained allow us to highlight how different subjects react under similar auditory/comprehension tests, in order to assess the similarity/dissimilarity of brain functional patterns, and, potentially, to detect the presence of any associated neurological disorders. The study confirms that all frequency bands can be used to characterize, under distinct events, the activation associated with a well-established auditory/comprehension test.