Figure 1.

Stimulus setup and structure of trial-block sequence. a, Example search frames in Experiment 1. Each search frame contained four neutral distractors (blue Ts), one target (red T) and one distractor item (green T). To isolate the target-related magnetic response (top row), the distractor was placed at the vertical meridian position with the target appearing at one of the two positions in the left (left) or the right visual field (right). The distractor-related response (bottom row) was isolated analogously way by placing the distractor at lateral positions, with the target appearing on the vertical meridian. The tERL or dERL was derived by subtracting the response to right visual field items from left visual field items; a subtraction that nulls the magnetic response elicited by the item placed on the vertical meridian. b, Illustration of trial-block structure and color assignment to the search items in Experiment 1–4. Each of the colored bars indicates the color assigned to the target (T) and distractor (D) on a given trial. The four neutral distractors were always blue in all experiments, and, except for Experiment 3, the task was always to determine the orientation of the target “T”.