EEG
HEP amplitude. Upward and downward directed HEP indicates positive and negative brain potentials, respectively (Fig. a Suppl El Mat).
Highs and lows exhibited similar HEP’s amplitudes (Fig. 2, averaged conditions) all over the brain - with the highs’ HEP sometimes slightly more positive than lows’ - except for the right parietal site (P4). At this site (Table a Suppl El Mat), a significant Group effect (p< .045) was observed in a time-window ranging from 256 ms to 312 ms, with a significantly lower HEP amplitude in highs than in lows (Table b Suppl El Mat) in B, R, IND1, Post. Moreover, quasi significantly lower values were observed in highs with respect to lows in the time intervals from 424 to 488 ms (p = .053) and from 536 ms to 592 ms, as illustrated in Fig 3a.