Determine the correlation of electrical activity between brain regions during a simple cognitive task in healthy volunteers.

High-density electroencephalography (HDEEG) recorded from scalp has been shown to provide utility for patients with medically refractory epilepsy undergoing pre-surgical planning. The two primary goals of pre-surgical planning are to identify a seizure onset zone, and to localize functional and dysfunctional regions. The latter is important to assess the potential risk of surgery. One main concern of epilepsy surgery is disrupting normal memory function. Currently, noninvasive tools to assess memory risks as part of pre-surgical workup are inadequate. In the current study, we recorded HDEEG during a simple cognitive task to assess network connectivity, which may elucidate widespread network dysfunction associated with cognitive problems.

Eight healthy adult volunteers underwent HDEEG during an auditory oddball task. Subjects were presented with common/standard and rare/target tones (1000 Hz and 2000 Hz, respectively) in an 80:20 ratio (pseudorandomized). Participants were asked to attend to the stimuli and count the number of rare/target tones. Source space data were estimated based on the scalp recordings. Correlations among current density at 88 Brodmann Areas were performed with 100ms windows, with 50ms overlap.

Early (50-150ms) waveforms are present for both stimulus types. This was reflected in correlations both among standards (Mean r=0.85; SD=0.08) and targets (Mean r=0.70; SD=0.13). During the P300 waveform (350-450ms post-stimulus), which only occurs during the rare/target tones, correlations for targets (Mean r=0.63; SD=0.13) were higher than standards (Mean r=0.36; SD=0.18).

These results suggest that HDEEG may serve as a noninvasive measure for reporting a robust biomarker of an established event-related potential (P300). Future studies will examine specific networks associated with cognitive processes and assess patients with known network dysfunction to determine whether this can be a useful tool for pre-surgical planning.