The late aspect of the distractor-elicited N2pc evident in Fig. 3b was not affected by this problem of signal

averaging because this aspect of the N2pc is specific to the distractor-related component. This possibility is provided some support in comparison of the distractor-elicited N2pc illustrated in Fig. 4b and the target-elicited N2pc illustrated in Fig. 1b; there is clear laterality in the 350–450 ms latency range in the distractor-elicited component but no corresponding activity in the target-elicited component. The late distractor-elicited N2pc might thus reflect residual activity not cancelled out by opposite-polarity, target-elicited N2pc. In summary, the present results demonstrate Microtubule Associated inhibitor a relationship between the resolution of perceptual ambiguity–as indexed by the N2pc–and feature OSI-744 molecular weight priming. We propose that as perceptual ambiguity increases, so does the need for attentional mechanisms responsible for ambiguity resolution. The action of these mechanisms has a residual effect such that subsequent

trials are affected. When these mechanisms act strongly and the target repeats, perceptual processing of the target is facilitated. In contrast, when target and distractor colors swap it is perceptual processing of the distractor that is facilitated, and this can result in the misallocation of attention to the distractor location. Ambiguity–and the attentional mechanisms responsible for resolving

it–appears to play an important role in feature priming. Fourteen healthy university students gave informed consent before beginning the experiment. All subjects reported normal or corrected-to-normal vision and were paid for their participation. Data from two participants were discarded due to excessive eye movement artifacts in the electroencephalogram (EEG; > 33% of trials tainted by eye movement artifacts). All MRIP of the remaining 12 participants (4 women; mean age 20.7 years ± 2.5 SD) were right handed. The experimental stimulus was a visual search array containing 6 shape stimuli, each equidistant (9.1°) from a central fixation point and each other (see figures for examples). Individual objects could be red or green outlines (0.3° line thickness) of diamonds (4.2° × 4.2°) or circles (3.4° diameter), and each contained a gray line (0.3° × 1.5°) randomly oriented vertically or horizontally. All stimuli were presented on a dark gray background. In each trial one of the objects was different in shape than the other five. This could mean that one object was a diamond with the other five objects circles or vice versa, with the identity of the shape singleton randomly determined for each trial. Participant response was based on the orientation of the line contained inside this shape singleton.