Figure 1.
Each trial began with a blink of the fixation diamond. After a jittered interval, the visual search items appeared (illustrated here by a target in the left visual field) and subjects were free to move their eyes and indicate whether the target “t” was upright or inverted. Targets appeared alone, with a neutral distractor, or a salient distractor. Note that items are not drawn to scale for illustrative clarity.
Figure 2.
First saccade latencies in each experimental condition in A) group and B) individuals. Error bars on group data are standard error of the mean. First saccade latencies were significantly faster for fs-distractor trials in the distractor-salient condition. This suggests that the salient distractor produced automatic oculomotor capture.
Figure 3.
Pre-stimulus (−1 -to 0 s) alpha activity is indicative of a bottom-up win.
A) Grand Average of the topography of pre-stimulus alpha power (8–12 Hz) for fs-distractor trials (left) and fs-target trials (right). The alpha activity is maximal at the central frontal electrodes. B) The time-frequency representations of fs-distractor (top) and fs-target trials (bottom) at the frontal central FCz electrode. C) The topography of the difference in pre-stimulus alpha- power between fs-distractor and fs-target trials. There was significantly greater pre-stimulus alpha in fs-distractor than fs-target trials. D) The stimulus locked N1 response. The peak amplitude of visual N1 response occurring at 0.175 s was bigger for fs-target trials (blue line) than fs-distractor trials (red line). E) The topography of the N1 response.
Figure 4.
Transient increase in theta/alpha (7–8 Hz) activity just prior to top-down saccade.
A) There was a transient alpha increase locked to the saccade onset. This transient increase was significantly larger for fs-target trials. B) The topography difference of the transient theta/alpha increase (mean −0.1 to 0 s) between fs-distractor and fs-target trials. C) The saccade locked ERPs for fs-distractor (red) and fs-target (blue) trials in both salient (thick lines) and none salient distractor (thin lines) conditions. A slow negative drift preceded the onset of all the saccades. The difference wave between fs-target and fs-distractor trials revealed a negative deflection. D) The topography of the negative deflection observed the in fs-target- fs-distractor difference wave.