Monolinguals and bilinguals disengage attention differently following conflict and errors: Evidence from ERPs.

Monolingual and bilingual young adults performed a task-switching experiment while EEG was recorded to investigate how bilingualism affects cognitive control following conflict. Participants were given pure blocks composed of three intermixed tasks, each consisting of univalent trials in which they responded to one feature of the stimulus - color, shape, or size. In the crucial conflict block, an irrelevant feature was added to one of the tasks, creating bivalent trials that included conflict. Behaviorally, all participants slowed responses to univalent trials that followed conflict, reflecting the post-conflict slowing effect. Electrophysiologically, monolinguals displayed longer-lasting post-conflict ERP effects and showed larger ERN amplitudes following responses than bilinguals, amplitudes that were associated with adjustments in response times. The interpretation is that bilinguals disengage attention following conflict from misleading stimuli or error responses more rapidly than do monolinguals.

MicroPET imaging of CD13 expression using a (64)Cu-labeled dimeric NGR peptide based on sarcophagine cage.

CD13 receptor as a tumor vasculature biomarker has attracted great attention in cancer research. Through phage display screening, NGR-containing peptides have been characterized as specific ligands binding to CD13 receptor. In this study, a (64)Cu-labeled dimeric NGR peptide based on sarcophagine cage was synthesized and evaluated for micropositron emission tomography (PET) imaging of CD13 expression in vivo. Macrocyclic chelating agent (sarcophagine cage) was conjugated with two azide moieties, followed by mixing with an alkyne-containing NGR peptide to rapidly provide the Sar-NGR2 peptide by click chemistry. Radiolabeling of Sar-NGR2 with (64)Cu was achieved in >90% decay-corrected yield with radiochemical purity of >99%. The cell uptake study showed that (64)Cu-Sar-NGR2 binds to CD13-positive HT-1080 cells, but not to CD13-negative MCF-7 cells. MicroPET imaging results revealed that (64)Cu-Sar-NGR2 exhibits good tumor uptake in CD13-positive HT-1080 xenografts and significantly lower tumor uptake in CD13-negative MCF-7 xenografts. The CD13-specific binding of (64)Cu-Sar-NGR2 was further verified by significant reduction of tumor uptake in HT-1080 tumor xenografts with coinjection of a nonradiolabeled NGR peptide. The biodistribution results demonstrated good tumor/muscle ratio (8.28 ± 0.37) of (64)Cu-Sar-NGR2 at 24 h pi in HT-1080 tumor xenografts, which is in agreement with the quantitative analysis of microPET imaging. In conclusion, sarcophagine cage has been successfully applied to the construction of a (64)Cu-labeled dimeric NGR-containing peptide. In vitro and in vivo studies demonstrated that (64)Cu-Sar-NGR2 is a promising PET probe for imaging CD13 expression in living mice.

How long-lasting is the post-conflict slowing after incongruent trials? Evidence from the Stroop, Simon, and flanker tasks.

The purpose of the present study was to determine how long-lasting the post-conflict slowing following incongruent stimuli is. In previous research, incongruent stimuli have been used to induce a conflict because they have relevant features for two different response alternatives. So far, the post-conflict slowing following incongruent stimuli has mainly been assessed up to one trial. In the first two experiments, we assessed the persistence of the post-conflict slowing across several trials. To this end, we presented a few incongruent stimuli among non-conflict stimuli. The results showed a consistent slowing for the first few trials immediately following the incongruent trials. In addition, a sporadic slowing was still found on later trials. In two subsequent experiments, we investigated to what extent the infrequency of incongruent trials - rather than their conflict - induced this slowing. To determine this, we used the same design as in the first two experiments, but we presented non-conflict stimuli as infrequent stimuli. The results showed a slowing on one subsequent trial, ruling out the possibility that the post-conflict slowing following incongruent trials was only caused by infrequency. Together, the findings of the present study indicate that the conflict induced by incongruent trials can have a longer lasting impact on subsequent trials than previously thought.

Support for a history-dependent predictive model of dACC activity in producing the bivalency effect: an event-related potential study.

In the present study, we examine electrophysiological correlates of factors influencing an adjustment in cognitive control known as the bivalency effect. During task-switching, the occasional presence of bivalent stimuli in a block of univalent trials is enough to elicit a response slowing on all subsequent univalent trials. Bivalent stimuli can be congruent or incongruent with respect to the response afforded by the irrelevant stimulus feature. Here we show that the incongruent bivalency effect, the congruent bivalency effect, and an effect of a simple violation of expectancy are captured at a frontal ERP component (between 300 and 550ms) associated with ACC activity, and that the unexpectedness effect is distinguished from both congruent and incongruent bivalency effects at an earlier component (100-120ms) associated with the temporal parietal junction. We suggest that the frontal component reflects the dACC's role in predicting future cognitive load based on recent history. In contrast, the posterior component may index early visual feature extraction in response to bivalent stimuli that cue currently ongoing tasks; dACC activity may trigger the temporal parietal activity only when specific task cueing is involved and not for simple violations of expectancy.