ERP analysis
Analysis of P1, N1 and SPN was based on average amplitude across
pre-registered spatiotemporal clusters. Electrodes were PO7, O1, O2 and
PO8 (highlighted in Figure 1). P1 was defined as the maximum amplitude
between 100 and 200 ms post stimulus onset in each participant and
condition. N1 was the minimum between 150 and 250 ms. N1 drop was then
computed as the difference from P1 peak. The SPN was computed as the
difference between symmetry and random waves in the 200-1000 ms window.
This was split into two sub-windows which differed in the pilot
experiment (early 200-400 and late 400-1000). Oddball trails were not
included in these analyses.
P300 was based on posterior central electrode cluster P1, PZ and P2 from
300-800 ms post stimulus onset. This was defined as the Oddball-Normal
difference (averaging over symmetry and random trials).