Overall distribution of the afterdischarges that occurred during stimulation at language sites shown in Fig. 5A–D. As with Fig. 4, this display therefore shows maxima but not trial-to-trial variations. The number at each electrode site and number labelling by the colour bar indicate the number of trials with afterdischarges at each electrode. For example, in (A), red indicates that afterdischarges occurred during six trials, as shown by the number 6 next to the red colour on the colour bar. This is also indicated by the number 6 at electrodes d9, d10 and d11. (Electrode d9 is in the fourth row from the top, the 9th electrode from the left, and d10 and d11 are to the right of d9; see the legend for Fig. 1.) The purple, red and blue bars between electrode pairs indicate where there were stimulation induced language, motor and sensory changes, respectively, and the green bars where there were no changes; these correspond to Fig. 1. The stimulated electrodes are circled. Afterdischarges are present in many locations, but are frequent at sites at which functional changes are similar. For example, in (A), afterdischarges occur six times at d10 and d11, and 4 times at b8 and b9, but they also occur at i12, i13 and j13. No function was found on testing i12–i13. No testing was performed at j12–j13 (see ‘Patients’ section), so we do not know whether this might have been a basal temporal language site (Lüders et al., 1986). In (B), afterdischarges were most frequent at d13, where language was found, but also at k12 and l12 in the basal temporal area, where it was not, and at k13, where no testing occurred. In (C), afterdischarges are most frequent at c8 and c9, where language was not found, but also, although less frequently, at a8, a9 and d13, where it was. In (D), afterdischarges occur frequently at b8–b9, but these are adjacent to a8–a9, and there are also afterdischarges at a10. Mouth function was affected by stimulation, so language could not be tested there.