Distribuição da atenção visual dentro de áreas indicadas: evidência baseada em julgamentos de ordem temporal

Three experiments were performed to investigate the distribution of attention across the visual field and the possibility of attentional resources to be more concentrated inside an abrupt onset frame (cue). The participants performed a temporal order judgment task of two letters presented in sequence; one letter presented inside and the other outside the frame. The results showed that the information presented inside the frame had its perceptual latency shortened in relation to the information presented outside the frame in experimental conditions where the frame orientation, the distance between the two letters and the cue onset time were manipulated. The advantage of the information presented inside the frame was attributed to the displacement of attention to the area delimited by the frame. The results contribute to the understanding of visual perception, showing that attentional resources may be redistributed inside the borders of a geometric figure.Três experimentos foram realizados para investigar a distribuição da atenção pelo campo visual e a possibilidade dos recursos de atenção serem mais concentrados no interior de uma moldura (dica) de início abrupto. Os participantes realizaram uma tarefa de julgamento de ordem temporal de duas letras apresentadas em seqüência; uma letra apresentada dentro e a outra fora da moldura. Os resultados mostraram que a informação apresentada dentro da moldura teve a sua latência perceptual encurtada em relação à informação apresentada fora da moldura em condições experimentais onde a orientação da moldura, a distância entre as duas letras e o tempo de exposição da moldura foram manipulados. Esta vantagem para a informação apresentada dentro da moldura foi atribuída ao deslocamento da atenção para a área delimitada pela moldura. Os resultados contribuem para o entendimento da percepção visual, mostrando que recursos de atenção podem ser redistribuídos dentro das bordas de uma figura geométrica.Co-ordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES

Eye contact facilitates awareness of faces during interocular suppression

Eye contact captures attention and receives prioritized visual processing. Here we asked whether eye contact might be processed outside conscious awareness. Faces with direct and averted gaze were rendered invisible using interocular suppression. In two experiments we found that faces with direct gaze overcame such suppression more rapidly than faces with averted gaze. Control experiments ruled out the influence of low-level stimulus differences and differential response criteria. These results indicate an enhanced unconscious representation of direct gaze, enabling the automatic and rapid detection of other individuals making eye contact with the observer

Is anyone looking at me? Direct gaze detection in children with and without autism

Atypical processing of eye contact is one of the significant characteristics of individuals with autism, but the mechanism underlying atypical direct gaze processing is still unclear. This study used a visual search paradigm to examine whether the facial context would affect direct gaze detection in children with autism. Participants were asked to detect target gazes presented among distracters with different gaze directions. The target gazes were either direct gaze or averted gaze, which were either presented alone (Experiment 1) or within facial context (Experiment 2). As with the typically developing children, the children with autism, were faster and more efficient to detect direct gaze than averted gaze, whether or not the eyes were presented alone or within faces. In addition, face inversion distorted efficient direct gaze detection in typically developing children, but not in children with autism. These results suggest that children with autism use featural information to detect direct gaze, whereas typically developing children use configural information to detect direct gaze

Intersubjective action-effect binding: Eye contact modulates acquisition of bidirectional association between our and others’ actions

In everyday social life, we predict others’ actions in response to our own actions.Subsequently, on the basis of these predictions, we control our actions to attain desired social outcomes and/or adjust our actions to accommodate the anticipated actions of the others. Representation of the bidirectional association between our and others’ actions, that is, intersubjective action-effect binding, could make such intersubjective action control easier and smoother. The present study investigated not only whether or not intersubjective action-effect binding was acquired but also whether or not eye contact modulated it. Experiment 1 showed that after a repeated experience during which participants’ finger movements triggered a target female individual’s mouth gesture, observing the target’s mouth gestures came to automatically trigger the participants’finger movements. Experiments 2 and 3 revealed that this effect was not observed when the target’s gaze direction was averted (Experiment 2) or when the target’s eyes were closed (Experiment 3) throughout the acquisition phase. These results indicate that intersubjective action-effect binding occurs and that an ostensive signal, that is, eye contact modulates it

Direct gaze facilitates rapid orienting to faces: evidence from express saccades and saccadic potentials

Direct gaze is a crucial signal in human social communication, which is known to attract visual attention and modulate a wide range of behaviours. The present study investigated whether direct gaze facilitates rapid orienting to faces, which is important for adaptive on-line communication, and its neural correlates. Fifteen participants performed a rapid orienting task, in which they were instructed to saccade to peripherally presented buildings or faces containing direct or averted gaze as quickly as possible. Electroencephalographic recordings were made during the task. Shorter express saccade latencies were found for faces with direct gaze, compared to averted gaze or buildings, while no significant difference was found between faces with averted gaze and buildings. Furthermore, saccade-locked event-related potential (ERP) amplitudes in parieto-occipital areas discriminated faces with direct gaze from buildings and faces with averted gaze corroborating behavioural results. These results show that detection of direct gaze facilitates rapid orienting to faces

Direct gaze partially overcomes hemispatial neglect and captures spatial attention

Direct gaze has been shown to be a particularly important social cue, being preferentially processed even when unconsciously perceived. Results from several visual search tasks further suggest that direct gaze modulates attention, showing a faster orientation to faces perceived as looking toward us. The present study aimed to analyze putative modulation of spatial attention by eye gaze direction in patients with unilateral neglect. Eight right hemisphere stroke patients with neglect performed a target cancellation paradigm. Patients were instructed to cross all open-eyed pictures amidst closed eyed distractors. Target images were either in direct or averted gaze. Participants performed significantly better when observing targets with direct gaze supporting the hypothesis that this gaze direction captures attention. These findings further suggest that perception of direct gaze is able to diminish the visuospatial impairment seen in neglect patients

Visual Pathways Serving Motion Detection in the Mammalian Brain

Motion perception is the process through which one gathers information on the dynamic visual world, in terms of the speed and movement direction of its elements. Motion sensation takes place from the retinal light sensitive elements, through the visual thalamus, the primary and higher visual cortices. In the present review we aim to focus on the extrageniculo-extrastriate cortical and subcortical visual structures of the feline and macaque brain and discuss their functional role in visual motion perception. Special attention is paid to the ascending tectofugal system that may serve for detection of the visual environment during self-motion

Opposite Influence of Perceptual Memory on Initial and Prolonged Perception of Sensory Ambiguity

Observers continually make unconscious inferences about the state of the world based on ambiguous sensory information. This process of perceptual decision-making may be optimized by learning from experience. We investigated the influence of previous perceptual experience on the interpretation of ambiguous visual information. Observers were pre-exposed to a perceptually stabilized sequence of an ambiguous structure-from-motion stimulus by means of intermittent presentation. At the subsequent re-appearance of the same ambiguous stimulus perception was initially biased toward the previously stabilized perceptual interpretation. However, prolonged viewing revealed a bias toward the alternative perceptual interpretation. The prevalence of the alternative percept during ongoing viewing was largely due to increased durations of this percept, as there was no reliable decrease in the durations of the pre-exposed percept. Moreover, the duration of the alternative percept was modulated by the specific characteristics of the pre-exposure, whereas the durations of the pre-exposed percept were not. The increase in duration of the alternative percept was larger when the pre-exposure had lasted longer and was larger after ambiguous pre-exposure than after unambiguous pre-exposure. Using a binocular rivalry stimulus we found analogous perceptual biases, while pre-exposure did not affect eye-bias. We conclude that previously perceived interpretations dominate at the onset of ambiguous sensory information, whereas alternative interpretations dominate prolonged viewing. Thus, at first instance ambiguous information seems to be judged using familiar percepts, while re-evaluation later on allows for alternative interpretations

Distributed Dendritic Processing Facilitates Object Detection: A Computational Analysis on the Visual System of the Fly

Hennig P, Möller R, Egelhaaf M. Distributed Dendritic Processing Facilitates Object Detection: A Computational Analysis on the Visual System of the Fly. PLoS ONE. 2008;3(8): e3092.Background: Detecting objects is an important task when moving through a natural environment. Flies, for example, may land on salient objects or may avoid collisions with them. The neuronal ensemble of Figure Detection cells (FD-cells) in the visual system of the fly is likely to be involved in controlling these behaviours, as these cells are more sensitive to objects than to extended background structures. Until now the computations in the presynaptic neuronal network of FD-cells and, in particular, the functional significance of the experimentally established distributed dendritic processing of excitatory and inhibitory inputs is not understood. Methodology/Principal Findings: We use model simulations to analyse the neuronal computations responsible for the preference of FD-cells for small objects. We employed a new modelling approach which allowed us to account for the spatial spread of electrical signals in the dendrites while avoiding detailed compartmental modelling. The models are based on available physiological and anatomical data. Three models were tested each implementing an inhibitory neural circuit, but differing by the spatial arrangement of the inhibitory interaction. Parameter optimisation with an evolutionary algorithm revealed that only distributed dendritic processing satisfies the constraints arising from electrophysiological experiments. In contrast to a direct dendro-dendritic inhibition of the FD-cell (Direct Distributed Inhibition model), an inhibition of its presynaptic retinotopic elements (Indirect Distributed Inhibition model) requires smaller changes in input resistance in the inhibited neurons during visual stimulation. Conclusions/Significance: Distributed dendritic inhibition of retinotopic elements as implemented in our Indirect Distributed Inhibition model is the most plausible wiring scheme for the neuronal circuit of FD-cells. This microcircuit is computationally similar to lateral inhibition between the retinotopic elements. Hence, distributed inhibition might be an alternative explanation of perceptual phenomena currently explained by lateral inhibition networks