Figure 4
Results of Experiment 3. Accuracy (a) and reaction times (b) as a function of number of elements for same (red) and different (green) luminance polarity conditions. (c) Grand average ERPs collapsed across number of elements for same (red) and different (green) luminance-polarity conditions. The ERPs are an average of the six channels (P7, P8, PO5, PO6, PO7, & PO8) used to quantify the N1 and N2 components and highlights the N2 effect between 250 and 400 ms after stimulus onset (yellow region and difference topography between all same and different polarity conditions). The blue regions indicate periods of stable topographic differences determined by TANOVA. (d) Grand average ERPs collapsed across luminance polarity for different number of elements. These ERPs are an average over electrodes FC1, FC3, C1, and C3, and show the LMF between 400 and 650 ms (yellow region and difference topography). The scalp topography is the difference between low (3, 4) minus high (5, 6) number of elements. TANOVA (blue regions) are also for low (3, 4) versus high (5, 6) number of elements. (e) Topographic microstates of grand averaged ERPs for all eight conditions. Horizontally oriented bars show the microstates through time for each condition (D3—different polarity stimuli with 3 elements, through to S6—same polarity stimuli with 6 elements). Each map is represented by a different colour. Global Field Power waveforms are displayed for a visual comparison to topographic microstates. (f) Four topographic microstates derived from the segmentation procedure which best fit the individual subject data. Topographic maps show the head from above with nasion plotted upward.
