Search

The aim of this study was to examine whether oscillatory activity in the theta-band is relevant for selective visuospatial attention when there is a need for the suppression of interfering and distracting information. A variant of the Eriksen flanker task was employed with bilateral arrays: one array consisting of a target and congruent or incongruent flankers and the second array consisting of neutral distractors. The bilateral arrays were preceded either by a 100% valid spatial cue or by a neutral cue. In the cue–target interval, a major burst in medial frontal theta power was observed, which was largest in the spatial cue condition. In the latter condition, additionally a posterior theta increase was observed that was larger over sites ipsilateral to the forthcoming target array. Functional connectivity analyses revealed that this pretarget posterior theta was related to the midfrontal theta. No such effects were observed in the neutral cue condition. After onset of the bilateral arrays, a major burst in posterior theta activity was observed in both cue conditions, which again was larger above sites ipsilateral to the target array. Furthermore, this posterior theta was in all cases related to the midfrontal theta. Taken together, the findings suggest that a fronto-posterior theta network plays an important role in the suppression of irrelevant and conflicting visual information. The results also suggest that the reciprocal relation between visuospatial attention and executive response control may be closer than commonly thought. [ABSTRACT FROM AUTHOR]

Redundant combination of target features from separable dimensions can expedite visual search. The dimension-weighting account explains these "redundancy gains" by assuming that the attention-guiding priority map integrates the feature-contrast signals generated by targets within the respective dimensions. The present study investigated whether this hierarchical architecture is sufficient to explain the gains accruing from redundant targets defined by features in different modalities, or whether an additional level of modality-specific priority coding is necessary, as postulated by the modality-weighting account (MWA). To address this, we had observers perform a visuo-tactile search task in which targets popped out by a visual feature (color or shape) or a tactile feature (vibro-tactile frequency) as well as any combination of these features. The RT gains turned out larger for visuo-tactile versus visual redundant targets, as predicted by the MWA. In addition, we analyzed two lateralized event-related EEG components: the posterior (PCN) and central (CCN) contralateral negativities, which are associated with visual and tactile attentional selection, respectively. The CCN proved to be a stable somatosensory component, unaffected by cross-modal redundancies. In contrast, the PCN was sensitive to cross-modal redundancies, evidenced by earlier onsets and higher amplitudes, which could not be explained by linear superposition of the earlier CCN onto the later PCN. Moreover, linear mixed-effect modeling of the PCN amplitude and timing parameters accounted for approximately 25% of the behavioral RT variance. Together, these behavioral and PCN effects support the hierarchy of priority-signal computation assumed by the MWA. [ABSTRACT FROM AUTHOR]

The biased competition account claims that competition between two stimuli increases when they are close together compared with when they are far apart. The reason is that nearby stimuli are more likely to be represented in the same receptive fields, requiring top–down or bottom–up biases to resolve the ambiguity. Consistent with biased competition, previous research showed that an index of attentional enhancement, the N2pc component, was attenuated when two targets were close together. In contrast, it is unclear whether distractor processing would also be attenuated when the distractor is close to the target. To answer this question, we used the additional singleton paradigm where a target is sometimes accompanied by a more salient, but entirely irrelevant, distractor. In the conditions of interest, the distance between the target and the distractor was systematically manipulated whereas the eccentricity to central fixation was always the same. The results showed that two indices of attentional suppression, the positivity posterior contralateral and distractor positivity components, were attenuated when the distractor was close to the target. Consistent with biased competition, attentional suppression of distractors was inhibited when the distance between target and distractor was short. The reduced attentional suppression of distractors with nearby targets may contribute to the increased behavioral interference with close distractors. [ABSTRACT FROM AUTHOR]