vs. 0.90 ±1.22), with no hemisphere difference for silent count (0.62 ±0.97 vs. 0.66 ±1.00). These response-related P3 source asymmetries were indirectly caused by superimposed anterior sinks contralaterally to the response hand, which are evident for both groups over left or right frontocentral sites for right or left button presses (Figure 5, rows 1 and 2) but not for silent count (Figure 5, row 3). Difference topographies between right or left press and silent count clarified that button press was associated with a superimposed, dipole-like sink-source generator pattern spanning the left or right motor cortex. While these lateralized, response-related dipoles were not completely symmetric for right and left button presses, they were highly comparable across groups. Finally, a significant task x hemisphere interaction resulted from opposite P3 source asymmetries, favoring the right hemisphere for tones (LH vs. RH, 0.76 ±1.18 vs. 0.85 ±1.16) and the left hemisphere for syllables (0.83 ±1.13 vs. 0.67 ±1.11), and these task-dependent asymmetries were present in both patients and controls (Figure 3, row 4).
