Negative versus positive priming: When are distractors inhibited?

Visual attention is guided by the history of selections in previous trials, an effect usually referred to as intertrial priming. The aim of the present study was to investigate whether such priming in visual search is due to a strengthening of the target signal, or the suppression of the distractor signal. In two experiments, we examined the deviation of saccade endpoints in situations in which the target and distractors were presented in relative close proximity. We found both negative and positive priming, irrespective of whether the repeating feature was relevant or irrelevant. This finding is in contrast to previous results with this paradigm, based on which we concluded that visual priming is strictly the result of boosting perceptual target signals. Based on the differences between these experiments, we conclude that the number of distractors is essential in observing negative priming. We propose that negative priming is solely observed when multiple distractors result in either strong inhibition of distractor features, or strong adaptation to them. Whereas positive priming seems to be a robust mechanism, negative priming is only present if there are multiple distractors.

Eye cannot see it: The interference of subliminal distractors on saccade metrics

AbstractThe present study investigated whether subliminal (unconsciously perceived) visual information influences eye movement metrics, like saccade trajectories and endpoints. Participants made eye movements upwards and downwards while a subliminal distractor was presented in the periphery. Results showed that the subliminal distractor interfered with the execution of an eye movement, although the effects were smaller compared to a control experiment in which the distractor was presented supraliminal. Because saccade metrics are mediated by low level brain areas, this indicates that subliminal visual information evokes competition at a very low level in the oculomotor system

The global effect: what determines where the eyes land?

In certain situations, the endpoint of an eye movement is not positioned on the centre of a target element, but deviates in the direction of another element. This phenomenon has been termed 'the global effect' and has proven to constitute a valuable measure of various processes that control and influence our oculomotor behavior. The goal of the current review is to provide insight in the factors that determine where the eyes land. We will focus on the fundamental characteristics of the global effect and discuss the various domains in which the global effect has been applied. The global effect appears to be best explained in terms of a weighted average of activity in a saccade map

Conditioned fear modulates visual selection

Eye movements reflect the dynamic interplay between top-down-and bottom-up-driven processes. For example, when we voluntarily move our eyes across the visual field, salient visual stimuli in the environment may capture our attention, our eyes, or modulate the trajectory of an eye movement. Previous research has shown that the behavioral relevance of a salient stimulus modulates these processes. This study investigated whether a stimulus signaling an aversive event modulates saccadic behavior. Using a differential fear-conditioning procedure, we presented a threatening (conditional stimulus: CS+) and a nonthreatening stimulus distractor (CS+) during an oculomotor selection task. The results show that short-latency saccades deviated more strongly toward the CS+ than toward the CS+ distractor, whereas long-latency saccades deviated more strongly away from the CS+ than from the CS+ distractor. Moreover, the CS+ distractor captured the eyes more often than the CS+ distractor. Together, these results demonstrate that conditioned fear has a direct and immediate influence on visual selection. The findings are interpreted in terms of a neurobiological model of emotional visual processing

Дуга нестабильности в украинской геополитике

Статья посвящена проблеме формирования геополитического вектора современной Украины. В статье показаны негативные, фактически кризисные явления и процессы в государственном строительстве Украины. Украина - рубежная страна между современным Западом и Востоком. Усиливающееся противостояние Запада и России может привести к расколу украинского общества и государства в целом. Устремленность политиков страны в сторону Запада несет восточнославянским народам огромный вред. Происходит подмена решения жизненноважных экономических проблем политическими акциями, направленными на раскол восточнославянских народов. Украина по воле ее руководителей становится организатором антироссийской политики в современных условиях. Попытки продвинуть идеи "оранжевой революции" при поддержке США на Восток не увенчались успехом, но наносят огромный экономический и иной вред государству и всему украинскому народу.Стаття присвячена проблемі формування геополітичного вектора Сучасної України. В статті показані негативні, фактично кризові явища і процеси в державному будівництві України. Україна - країна рубежу між сучасним Заходом і Сходом. Протистояння Заходу і Росії, що посилюється, може привести до розколу українського суспільства і держави в цілому. Спрямованість політиків країни у бік Заходу несе східно-слов'янським народам величезну шкоду. Відбувається підміна рішення життєважливих економічних проблем політичними акціями, направленими на розкол східнослов'янських народів. України по волі її керівників стає організатором антиросійської політики в сучасних умовах. Спроби просунути ідеї "оранжевої революції" при підтримці США на схід не увінчалися успіхом, але наносять величезний економічний і інша шкода державі та всьому українському народу.The article is devoted to the problem of forming of geopolitical vector of Modern Ukraine. The negative, actually crisis phenomena and processes in state building of Ukraine are shown in the article. Ukraine is a border country between modern the West and the East. Increasing opposition of the West and Russia can result in the dissidence of Ukrainian society and state on the whole. The tendency of politicians of country toward the West carries enormous harm to the east Slavonic people. There is substitution of decision economic problems by the political actions directed on the dissidence of eastslavonic people. Ukraine on will of its leaders becomes the organizer of anti-russian policy in modern terms. Attempts to move forward the ideas of "orange revolution" at support of the USA east were not crowned by success, but inflict enormous economic and other harm to the state to all Ukrainian people

Shift and deviate: Saccades reveal that shifts of covert attention evoked by trained spatial stimuli are obligatory

The premotor theory of attention predicts that motor movements, including manual movements and eye movements, are preceded by an obligatory shift of attention to the location of the planned response. We investigated whether the shifts of attention evoked by trained spatial cues (e.g., Dodd & Wilson, 2009) are obligatory by using an extreme prediction of the premotor theory: If individuals are trained to associate a color cue with a manual movement to the left or right, the shift of attention evoked by the color cue should also influence eye movements in an unrelated task. Participants were trained to associate an irrelevant color cue with left/right space via a training session in which directional responses were made. Experiment 1 showed that, posttraining, vertical saccades deviated in the direction of the trained response, despite the fact that the color cue was irrelevant. Experiment 2 showed that latencies of horizontal saccades were shorter when an eye movement had to be made in the direction of the trained response. These results demonstrate that the shifts of attention evoked by trained stimuli are obligatory, in addition to providing support for the premotor theory and for a connection between the attentional, motor, and oculomotor systems

Shift and deviate: Saccades reveal that shifts of covert attention evoked by trained spatial stimuli are obligatory

The premotor theory of attention predicts that motor movements, including manual movements and eye movements, are preceded by an obligatory shift of attention to the location of the planned response. We investigated whether the shifts of attention evoked by trained spatial cues (e.g., Dodd & Wilson, 2009) are obligatory by using an extreme prediction of the premotor theory: If individuals are trained to associate a color cue with a manual movement to the left or right, the shift of attention evoked by the color cue should also influence eye movements in an unrelated task. Participants were trained to associate an irrelevant color cue with left/right space via a training session in which directional responses were made. Experiment 1 showed that, posttraining, vertical saccades deviated in the direction of the trained response, despite the fact that the color cue was irrelevant. Experiment 2 showed that latencies of horizontal saccades were shorter when an eye movement had to be made in the direction of the trained response. These results demonstrate that the shifts of attention evoked by trained stimuli are obligatory, in addition to providing support for the premotor theory and for a connection between the attentional, motor, and oculomotor systems

Discriminating between anticipatory and visually triggered saccades:measuring minimal visual saccadic response time using luminance

We describe a novel behavioral method to accurately discriminate anticipatory (i.e., saccades not generated by visual input) from visually triggered saccades and to identify the minimal visual saccadic reaction time (SRT). This method can be used to calculate a feasible lower bound cutoff for latencies of visually triggered saccades within a certain experimental context or participant group. We apply this method to compute the minimal visual SRT for two different saccade target luminance levels. Three main findings are presented: 1) the minimal visual SRT for all participants was 46 ms shorter for bright targets than for dim targets, 2) the transition from non-visually triggered to visually triggered saccades occurred abruptly, independent of target luminance, and 3) although the absolute minimal visual SRTs varied between participants, the response pattern (response to bright targets being faster than to dim targets) was consistent across participants. These results are consistent with variability in saccadic and neural responses to luminance as has been reported in monkeys. On the basis of these results, we argue that differences in the minimal visual SRT can easily occur when stimuli vary in luminance or other saliency features. Applying an absolute cutoff (i.e., 70-90 ms) that approaches the minimal neuronal conduction delays, which is general practice in many laboratories, may result in the wrongful inclusion of saccades that are not visually triggered. It is suggested to assess the lower SRT bound for visually triggered saccades when piloting an experimental setup and before including saccades based on particular latency criteria. NEW & NOTEWORTHY We successfully developed an anticipation paradigm to discriminate between anticipatory and visually triggered saccades by measuring the minimal visual saccadic response time (SRT). We show that the 70- to 90-ms lower bound cutoff for visually triggered saccades should be applied in a flexible way and that the transitional interval is very short. The paradigm can be employed to investigate the effects of different stimulus features, experimental conditions, and participant groups on the minimal visual SRT in humans

Intra-saccadic displacement sensitivity after a lesion to the posterior parietal cortex

Visual perception is introspectively stable and continuous across eye movements. It has been hypothesized that displacements in retinal input caused by eye movements can be dissociated from displacements in the external world using extra-retinal information, such as a corollary discharge from the oculomotor system. The extra-retinal information can inform the visual system about an upcoming eye movement and accompanying displacements in retinal input. The parietal cortex has been hypothesized to be critically involved in integrating retinal and extra-retinal information. Two tasks have been widely used to assess the quality of this integration: double-step saccades and intra-saccadic displacements. Double-step saccades performed by patients with parietal cortex lesions seemed to show hypometric second saccades. However, recently idea has been refuted by demonstrating that patients with very similar lesions were able to perform the double step saccades, albeit taking multiple saccades to reach the saccade target. So, it seems that extra-retinal information is still available for saccade execution after a lesion to the parietal lobe. Here, we investigated whether extra-retinal signals are also available for perceptual judgements in nine patients with strokes affecting the posterior parietal cortex. We assessed perceptual continuity with the intra-saccadic displacement task. We exploited the increased sensitivity when a small temporal blank is introduced after saccade offset (blank effect). The blank effect is thought to reflect the availability of extra-retinal signals for perceptual judgements. Although patients exhibited a relative difference to control subjects, they still demonstrated the blank effect. The data suggest that a lesion to the posterior parietal cortex (PPC) alters the processing of extra-retinal signals but does not abolish their influence altogether