Figure 1.

An example of the visual stimulation employed and a schematic demonstration of the visual sequence. The subjects' task was to focus on the center of the screen to detect combinations of two concentric circles, which were present continuously but changed colors pseudorandomly at every SOA refresh. At the same time, unattended orthographic stimuli were presented briefly (100 ms) at symmetrical locations on visual periphery (at 2.5° angle from the center to the left and to the right) in oddball sequences containing frequent standard and rare unexpected deviant stimuli (see also Table 1). In addition to the set of oddball blocks, a sensory visual baseline condition was included that only contained concentric circles but no orthogprahic stimuli on the flanks.