Article Figures & Data
Figures
- Figure 1.
Example stimuli from the two experiments. a, Experiment 1 task. One color was designated the target color at the beginning of each block and participants were instructed to report whether the target-colored circle had a gap on the top or on the bottom. Target location varied unpredictably from trial to trial. b, Experiment 2 task. One color was designated as the target color at the beginning of each block. Participants were instructed to report whether the middle letter in the set of letters of this color was a vowel or a consonant. The middle letter was always on the horizontal meridian and the flankers could be absent, 1.6° above and below the middle letter, or 0.9° above and below the middle letter. The side containing the target color varied unpredictably from trial to trial.
- Figure 2.
HEOG waveforms (after artifact rejection) for left-side and right-side targets in Experiments 1 (a) and 2 (b). The scale of ±16 μV reflects a horizontal eye deviation of ±1°. Therefore, on average, the residual eye movements were negligible (<0.1°).
- Figure 3.
Mean correct response rate (a) and mean RT (b) for Experiment 1. *p < 0.05. Error bars indicate the within-subjects SEM.
- Figure 4.
Grand average ERPs from Experiment 1. Contralateral and ipsilateral ERP waveforms are shown for targets in the upper VF (a) and lower VF (b). c, Contralateral-minus-ipsilateral difference waves. d, Mean N2pc amplitude measured from the difference waves. Error bars indicate the within-subjects SEM. #p < 0.05 for difference from zero. *p < 0.05 for comparison of upper and lower VFs.
- Figure 5.
Topographic plots of the averaged ERP during the N2pc window for left and right targets and for the contralateral-minus-ipsilateral difference for upper VF (a) and lower VF (b) targets. Given the way the data are combined to derive the N2pc component, the left and right hemispheres are necessarily mirror images. The typical occipitotemporal N2pc scalp distribution was observed for the lower VF (b, right), but little or no contralaterality was observed for the upper VF target condition (a, right).
- Figure 6.
Grand average TF plots from Experiment 1. a, Upper VF targets that elicited approximately equivalent suppression of alpha-band power for both contralateral and ipsilateral electrodes relative to the target location (a.3). b, Lower-field targets, which elicited greater alpha-band suppression over the contralateral hemisphere (b.3). The white region at the bottom right corner of the plots indicates values that are undefined given the epoch length and wavelet duration. c, Time course of the contralateral-minus-ipsilateral difference in alpha-band power.
- Figure 7.
Topographic plots of induced alpha band (8–12 Hz) activity during the N2pc time window for left and right targets and for the contralateral-minus-ipsilateral difference for upper VF (a) and lower VF (b) targets. A lateralization effect was observed for lower VF targets (b, right), but not for upper VF targets (a, right).
- Figure 8.
Topographic plots of induced alpha band (8–12 Hz) activity during a longer time window (200–1200 ms) for left and right targets and for the contralateral-minus-ipsilateral difference for upper VF (a) and lower VF (b) targets. A lateralization effect was observed for lower VF targets (b, right) but not for upper VF targets (a, right).
- Figure 9.
Mean correct response rate (a) and RT (b) for Experiment 2. This is a typical pattern showing decreased accuracy and longer RT for the most crowded conditions. Error bars indicate the within-subjects SEM. *p < 0.05 for pairwise comparison.
- Figure 10.
Experiment 2 grand-averaged ERPs. Contralateral and ipsilateral ERP waveforms are shown for the no-flankers condition (a), 1.6° condition (b), and 0.9° condition (c). d, Contralateral-minus-ipsilateral difference waves. e, Bar plots for the N2pc time window. Error bars indicate the within-subjects SEM. #p < 0.05 for one-sample t test against zero. *p < 0.05 for pairwise comparison. There was a significant N2pc effect only for the 1.6° condition.
- Figure 11.
Topographic plots of the averaged ERP during the N2pc time window for left and right targets and for the contralateral-minus-ipsilateral difference for the no-flankers condition (a), 1.6° condition (b), and 0.9° condition (c). The N2pc showed a typical occipitotemporal distribution for the 1.6° condition.
- Figure 12.
Grand-average TF plots from Experiment 2. Shown are contralateral, ipsilateral, and contralateral-minus-ipsilateral differences for the no-flankers condition (a), 1.6° condition (b), and 0.9° conditions (c). Target processing elicited greater alpha-band suppression over the contralateral hemisphere (right panels). The white region at the bottom right corner of the plots indicates values that are undefined given the epoch length and wavelet duration. d, Time course of the contralateral-minus-ipsilateral difference in alpha-band power.
- Figure 13.
Topographic plots of induced alpha band (8–12 Hz) activity during the N2pc time window for left and right targets and for the contralateral-minus-ipsilateral difference for the no-flankers condition (a), 1.6° condition (b), and 0.9° condition (c). Unlike the N2pc component, greater contralaterality was observed for the most crowded condition (c, right).
- Figure 14.
Topographic plots of induced alpha band (8–12 Hz) activity during a longer time window (200–1200 ms) for left and right targets and for the contralateral-minus-ipsilateral difference for the no-flankers condition (a), 1.6° condition (b), and 0.9° condition (c). Unlike the N2pc component, greater contralaterality was observed for the most crowded condition (c, right).
Tables
- Table 1.
Correlations between alpha-band (8–12 Hz) power measured at different time windows with the N2pc and behavioral measures (RT and CR) for Experiment 1 and Experiment 2
Alpha 156–276 ms Alpha 200–600 ms Alpha 600–900 ms Alpha 900–1200 ms Experiment 1 Upper VF target RT r = 0.22 (p = 0.33) r = 0.38 (p = 0.08) r = 0.63 (p = 0.002)* r = 0.43 (p = 0.05)* Correct response rate r = −0.26 (p = 0.24) r = −0.09 (p = 0.68) r = −0.18 (p = 0.42) r = −0.15 (p = 0.5) N2pc r = 0.18 (p = 0.43) r = −0.44 (p = 0.046)* r = −0.16 (p = 0.48) r = −0.1 (p = 0.63) Lower VF target RT r = −0.3 (p = 0.62) r = 0.18 (p = 0.42) r = −0.1 (p = 0.66) r = −0.12 (p = 0.6) Correct response rate r = 0.11 (p = 0.62) r = 0.04 (p = 0.85) r = −0.11 (p = 0.63) r = −0.18 (p = 0.41) N2pc r = 0.16 (p = 0.47) r = 0.39 (p = 0.074) r = 0.16 (p = 0.47) r = 0.11 (p = 0.64) Alpha 132–252 ms Alpha 200–600 ms Alpha 600–900 ms Alpha 900–1200 ms Experiment 2 No flankers RT r = 0.04 (p = 0.84) r = 0.23 (p = 0.32) r = −0.03 (p = 0.87) r = −0.042 (p = 0.85) Correct response rate r = 0.35 (p = 0.11) r = 0.43 (p = 0.048)* r = 0.29 (p = 0.18) r = 0.56 (p = 0.007)* N2pc r = 0.23 (p = 0.31) r = −0.035 (p = 0.87) r = 0.03 (p = 0.87) r = 0.1 (p = 0.65) 1.6° RT r = 0.22 (p = 0.32) r = 0.13 (p = 0.55) r = 0.084 (p = 0.71) r = −0.16 (p = 0.49) Correct response rate r = 0.01 (p = 0.96) r = 0.05 (p = 0.82) r = 0.23 (p = 0.29) r = 0.22 (p = 0.33) N2pc r = −0.019 (p = 0.93) r = 0.13 (p = 0.56) r = 0.14 (p = 0.52) r = 0.06 (p = 0.79) 0.9° RT r = −0.28 (p = 0.21) r = −0.05 (p = 0.81) r = 0.06 (p = 0.79) r = −0.23 (p = 0.3) Correct response rate r = 0.13 (p = 0.56) r = 0.24 (p = 0.28) r = 0.25 (p = 0.27) r = 0.2 (p = 0.36) N2pc r = −0.56 (p = 0.008)* r = −0.09 (p = 0.69) r = −0.14 (p = 0.54) r = −0.08 (p = 0.71) ↵*p < 0.05.
