Article Figures & Data
Figures
- Figure 1.
A, Spatial dimensions of the stimuli, which were presented to subjects at the center of the screen. B, Individual trial timeline with durations of each screen presentation. Note that on 25% of the trials the target was replaced with a blank screen to create a mask-only condition and on 25% of the trials the mask was replaced by a blank screen to create a target-only condition.
- Figure 2.
A, Average linear trends over the course of an experimental block for detection rate and false alarm rate (solid lines), and for d′ and criterion (c; dashed lines). The least squares regression line of best fit for each curve is shown in gray. B, Overall detection rate (left) contrasted with detection rate as a function of detection on the previous target-plus-mask trial (center: detected; right: undetected). *p < 0.05. n.s., Not significant at α = 0.05; error bars represent within-subject SE.
- Figure 3.
Grand average ERP waveforms elicited by the fixation cross at channel T5 (star) for detected (solid) and undetected (dashed) trials. Shaded waveform regions represent analyzed time windows in which the mean voltage was reliably greater in the trials in which observers later detected targets compared with trials in which the target would later be undetected. Interpolated scalp voltage maps of the difference between detected and undetected trials at the peak difference for both the P1 and P2 components.
- Figure 4.
A, Detection rate plotted as a function of prestimulus log-transformed α power quartiles revealing a significant decrease in target detection with increased power; *p < 0.05. B, Detection rate plotted as a function of opposite phases of prestimulus α phase, comparing high- and low-power trials. The effect of phase was only present for high power trials. **p < 0.005; n.s., not significant at α = 0.05; error bars represent within-subject SE. C, Circular histogram of the difference in mean phase of α activity between detected and undetected targets indicating a non-zero difference in phase. Distance from origin reflects the number of subjects whose difference vector falls within each phase quadrant, indicated by dashed gray lines. The blue arrow represents the average difference in mean phase across subjects. D, Two overlaid circular histograms of the mean phase of α activity preceding both detected (blue) and undetected (red) targets. Arrows represent the average phase of α across subjects for each condition. E, Results of a bootstrap analysis of the mean phase of α activity preceding detected and undetected targets. An equal number of trials were randomly sampled from each condition with replacement for each subject. The grand average phase of each of these samples was obtained for each condition and plotted on the chart. Vectors represent the mean across all bootstrapped samples. There is a clear separation of the mean phase of α between the two conditions, equating trial numbers. F, Grand average ERP at channel Pz in the 100 ms preceding and after the onset of the target. Note the opposite phase for the undetected (dashed) and detected (solid) targets. When collapsed across all targets, no phase-locking is apparent (gray).
- Figure 5.
Difference waves created by subtracting ERPs on mask-only trials from masked target trials, yielding waveforms representing the activity resulting from the detected (solid) and undetected (dashed) targets, plotted at three locations (Fz, Pz, Oz) along the midline. Shaded waveform regions represent analyzed time windows in which the mean voltage was reliably greater for detected targets than for undetected targets. Stars represent channels from which analysis measurements were taken for each component. Interpolated scalp voltage maps of the difference between detected and undetected trials at the peak difference for components P1, N1, P2, and P3.
