Table 1.
Chromaticity coordinates (x,y,Y CIE1931) of test stimuli and background.
Fig 1.
General task procedure of the passive visual oddball ERP task.
On each trial a coloured square was presented to the UVF and another simultaneously to the LVF. Participants attended to a fixation dot and responded on those trials in which it changed shape. For the majority of trials both squares were the standard (boundary) stimulus. The remaining trials presented either a green or blue deviant stimulus to the UVF or LVF. Stimuli were presented for 200 ms with a randomised interstimulus interval of 1,000 ms ± 200 ms.
Fig 2.
Grand-averaged ERP waveforms elicited in response to standard and deviant colours presented to the lower visual field.
(A) Waveforms elicited for 800 ms following stimulus onset summarised over nine representative electrode locations. Stimuli were classified as same- or different-category to the standard for each individual based on their naming of the standard stimulus as blue or green. Electrode locations are provided towards the top of the y-axes. ERP components (e.g., P1) are labelled on one waveform each. N1ant denotes the anterior N1 component, N1post denotes the posterior N1, FP denotes frontal positivity, N2ant denotes the anterior N2, and N2post denotes the posterior N2. (B) A category effect in P1 over a refined time period (94–104 ms): The different-category deviant elicited a significantly more negative mean amplitude than the same-category deviant displayed here at a representative electrode (O1). (C) Topographic map showing the amplitude difference (same- minus different-category deviant of the the P1 effect. The arrow shows the location of representative electrode O1).
Table 2.
Summary of analyses of ERP components from two-way mixed ANOVAs containing the factors of category (within-subjects; 3 levels: standard, same- and different-category deviant) and group (between-subjects; 2 levels: blue namers vs. green namers), N = 30.
Table 3.
Linear regression analyses applied to multiple ERP components modelling the relationship between naming consistency of a boundary blue-green colour (i.e., the standard stimulus) and the difference in mean amplitude (μV) elicited by a same- and different-category deviant colours presented to the UVF or LVF (N = 30).