Fig. 3.
Task-specific changes in the spatial pattern of theta/HG coupling strength. (A) Theta/HG coupling strength falls to chance at large time lags. Modulation index (25)asa function of lag for all electrodes over all tasks from subject 5. Electrodes are sorted by the time-lag τmax associated with maximal coupling (black line). For ease of comparison, horizontal traces were renormalized so that the peak value for each channel is one (see also fig. S8). (B) The change in modulation index values from the mean for all electrodes in subject 2 during one task (passive listening to predictable tones). (C) As in (B), for a difficult working memory task. Subjects listened to a list of phonemes and responded when the current phoneme and the phoneme presented two items earlier were identical. (D) Similar tasks evoke similar spatial patterns of theta/HG coupling. Correlation matrix for all tasks in subject 2. Tasks: 1 to 4, passive listening to tones or phonemes; 5, mouth motor activation; 6, verb generation; 7, hand motor activation; 8 to 11 auditory working memory; 12 and 13, linguistic target detection; 14 to 17, auditory-vibrotactile target detection (see SOM text). (E) Mean correlation and standard error between similar tasks (positive, P < 0.01, corrected, 58 task pairs) as well as different tasks (not significant, 617 task pairs) for all electrodes in all subjects over all tasks.