Electrophysiological revelations of trial history effects in a color oddball search task

Saliency affects attentional capture and suppression of abrupt-onset and color singleton distractors: Evidence from event-related potential studies

Attention is the process of selecting relevant information and suppressing irrelevant information. However, it is still controversial whether attentional capture by salient but task-irrelevant stimuli operates in a bottom-up fashion (stimulus-driven theory) or a top-down fashion (goal-driven theory) or if even salient distractors can be suppressed before capturing attention (signal suppression theory). In the present study, we investigated how saliency affects attentional capture (indexed by N2-posterior-contralateral [N2pc]) and suppression (indexed by distractor positivity [P_D ]) of abrupt-onset and color singleton distractors in a visual search task. Experiment 1 showed that an abrupt-onset distractor elicited both N2pc and P_D , while a color singleton distractor elicited only P_D . Moreover, the abrupt-onset distractor elicited a larger N2pc and a larger P_D relative to the color singleton distractor. In addition, both distractors elicited an early positive component, the positivity posterior contralateral (Ppc), which was also larger for abrupt onsets than for color singletons. Experiment 2 further demonstrated that when both the abrupt onset and color singleton were designed as targets, and thus required no attentional suppression, Ppc was elicited, but P_D was not. This corroborated the finding in Experiment 1 that the later P_D , not the early Ppc, reflected attentional suppression. Therefore, a more salient distractor demonstrates stronger early perceptual processing, can capture attention better and needs more attentional resources to be suppressed later. Based on these results, a three-stage hypothesis is proposed, in which the saliency of a distractor modulates processing at early perception, attentional capture, and suppression stages.

From alternation to repetition: Spatial attention biases contribute to sequential effects in a choice reaction-time task

Observers often take longer to respond to a visual target when it appears at a recently stimulated location than when it appears at a new location in the visual field. This behavioral impairment - known as inhibition of return (IOR) - is mirrored by a reduction of an event-related potential (ERP) component called the N2pc that has been associated with attentional selection. Together, these findings indicate that the mechanism underlying IOR operates to bias covert attention against re-visiting the most recently attended location. The goal of the present study was to determine how this inhibitory attention bias evolves across successive trials of a two-item search task. Initially, targets appearing at previously attended locations were associated with behavioral IOR and a concomitant reduction of the N2pc. After several successive trials, this initial inhibitory bias was superseded by expectancy-based biases associated with "predictable" inter-trial patterns of location repeats or location changes, in some cases leading to faster responses and a larger N2pc when the target location repeated (facilitation of return).  These results provide evidence that biases in the covert deployment of attention are updated dynamically according to the recent selection history and contribute to well-known sequential effects in serial choice reaction-time tasks.

Differential inter-trial effects in the visual search of children, adolescents, and young adults

We examined the age-related variation in one type of inter-trial effect of visual search, the distractor previewing effect (DPE), in affectively neutral and affectively charged contexts. In Experiment 1, children, adolescents, and young adults were faster to identify the shape of a color target when the color of the current distractors had already been previewed than when the target had been previewed in the preceding target-absent trial, indicative of a color-based DPE. The results revealed a greater DPE in children than in adolescents and young adults, but it can be attributed to children's slower RTs than the other two groups. In Experiment 2, children, adolescents, and young adults were instructed to respond to a schematic face that was different from the other two faces. Young adults were faster in searching for a threatening face among friendly ones when they had previewed a target-absent display consisting of friendly faces than that of threatening faces, indicating an emotional DPE. By contrast, children showed a reversed DPE under the same condition, whereas adolescents showed no DPE. Taken together, these results suggested that the three age groups were all able to create an inhibitory attentional bias on the basis of trial history in affectively neutral context, whereas children and adolescents were not able to create such an inhibitory attentional bias in affectively charged contexts in the same way as adults did. These findings implied that the development of attentional inhibition abilities in affectively charged contexts might be delayed compared to those in affectively neutral contexts.

The neural correlation of sustained attention in performing conjunctive continuous performance task: an event-related potential study

Owing to great improvements in cognitive neuroscience, the study of brain functions during different types of cognitive tasks has attracted much attention. Recording event-related potentials (ERPs) is an appropriate tool for such a purpose, as it is noninvasive and affordable. Attention is among the most studied cognitive processes. In this study, a visual version of the conjunctive continuous performance task-visual was used to examine the differences of cognitive processes in target and nontarget stimuli. Twenty healthy individuals (average age: 23 years) participated in the study. Electroencephalogram signals were recorded from all participants during conjunctive continuous performance task-visual. After preprocessing, the ERPs were calculated by averaging the epochs that were time-locked to the stimulus onset. Then, the ERPs of the two groups of target and nontarget stimuli, from the aspects of differences in the P300 and N200 morphological features, were analyzed in three midline channels: Pz, Fz, and Cz. According to the results, the P300 amplitudes were significantly larger in the target than those in the nontarget stimuli. The P300 latencies were also larger in the target than in the nontarget stimuli, but the difference was only significant in the Pz channel ERPs. For the N200 component, the negativity of amplitudes was significantly more enhanced in the target than in the nontarget stimuli. However, for the N200 latencies, no significant difference was found based on the data obtained from the groups. Furthermore, the findings suggest that the distribution of the P300 component is more centroparietal for the target stimuli, and more centrofrontal for the nontarget ones. In addition, the distribution of the N200 component is more frontoparietal for both the target and nontarget stimuli.