Fig. 3.

Summary of methods. (A) Subdural electrode arrays were placed on the cortical surface based on clinical considerations. (B) A 3-min fixation task served as the resting state. (C) Repetitive finger movement. Patients 1 and 2 performed repetitive flexion–extension of either the thumb or the forefinger of the right or left hand in response to random interleaved visual cues. (D) Verb generation. Patient 1 performed a verb generation task, where a list of concrete nouns was serially presented on a screen 1 m away, during which time an associated verb would be stated. (A) Visual target detection. Patients 2 and 3 performed an engaged target detection task, with pictures of houses (and faces also for patient 3) with vocally reported targets. (E–J) Signal processing. Nearest-neighbor electrode potential pair difference channels were used to isolate the most local cortical activity (A, E–G). A band-pass filter for 76–200 Hz (x-band, ref. 16) was applied (H) (Butterworth filters, with notch filters at 60 Hz harmonics for ambient line noise). The signal element was squared and summed to obtain the power in nonoverlapping 400-ms blocks (I and J). The distributions of resting (fixation) and active blocks (mean and standard error shown in Figs. 1 and 2) were compared by using an unpaired t test, and the resulting P value from each electrode pair was Bonferroni corrected for the total number of medial pairs. Representative pairs are shown, but some others were significant, with increase or decrease clustered by task and region. All electrodes included in this study were far (>2.5 cm) from any cortical lesion or epileptic focus.