Figure 2. The d′-values of response in different frequency bands during the arithmetic condition.

The three plots show the d′-values (vertical axis) of parietal electrodes in different frequency ranges (horizontal axis) in participants P1, P2 and P3. The horizontal dashed line represents the d′-value of 0.75 (the higher the d′-values, the more selective activity during the experimental arithmetic condition). Each dot represents one electrode selected to be within the anatomical boundaries of the parietal lobe. Electrodes with significant increase of HFB activity during the experimental arithmetic condition are filled in red. Interestingly, none of these electrodes showed increase of activity in lower frequency bands during the arithmetic condition.