Table 1.

The table shows the mean amplitudes and standard deviations in the selected interval of 142–198 ms, from fronto-central and parietal derivations, for the standard and deviant conditions that were grouped together for the three different tasks.

		Mean amplitude ± SD [μV]; n = 12; 142–198 ms
Task	Condition	Fronto-central a.	Centro-parietal a.
Fixation	Standard	−2.74 ± 1.31	−2.16 ± 1.12
	Deviant	−2.96 ± 1.16	−2.38 ± 1.12
Easy	Standard	−2.32 ± 1.62	−1.75 ± 1.67
	Deviant	−2.98 ± 1.67	−2.16 ± 1.43
Difficult	Standard	−2.16 ± 1.71	−1.84 ± 1.54
	Deviant	−2.85 ± 1.21	−2.52 ± 1.17

The grand average ERPs, regions and the intervals of interest are depicted in Figure 2.