Reflexive Shifts Of Attention Research Articles

Le phénomène de l’inhibition de retour dans la schizophrénie : revue de la littérature

Most visual environments contain more information than the human brain can process in real time. To overcome this limitation, the attention system acts as a filter by selectively orienting attention to specific regions of the visual field. This ability to orient attention can be reflected in covert shift processes of attention. In a typical covert orienting task, subjects have to maintain fixation on a central cross and respond as quickly as possible to a target, which appears in a peripheral box following a cue that summons attention to the direction where the target is going to appear (valid cueing) or to the contralateral direction (invalid cueing). When the cues are nonpredictive, the response characteristics critically depend on stimulus-onset asynchrony (SOA). With short SOAs (<300ms), valid cues result in a reaction time advantage over invalid trials, which is due to a reflexive shift of attention towards the source of stimulation. In contrast, with longer SOAs, valid cues result in longer reaction times to the subsequent target. This phenomenon is known as the inhibition of return and is mostly thought to reflect an inhibitory mechanism protecting the organism from redirecting attention to previously scanned insignificant locations. Many studies have reported blunted or delayed inhibition of return in patients with schizophrenia. However, some authors reported normal amounts of inhibition of return. This can be partly explained by the use of manipulations of the covert orienting of the attention paradigm that is known to enhance the course of inhibition of return. The deficit of inhibition of return seems to be time-stable and to be unrelated to psychopathology or length of illness. The contribution of neuroleptic medication to this deficit cannot be determined. Recent data suggest a deficit of inhibition of return in two human models of psychosis (dimethyltryptamine and ketamine). Further studies should clarify whether blunted inhibition of return might represent a trait marker of schizophrenia.

Attentional shift by gaze is triggered without awareness

Reflexive attentional shift in response to another individual's gaze direction has been reported, but it remains unknown whether this process can occur subliminally. We investigated this issue using facial stimuli consisting of drawings (Experiment 1) and photographs (Experiment 2). The gaze direction was expressed by the eye gaze direction (Experiment 1), and the eye gaze and head direction (Experiment 2). The gaze cue was presented either supraliminally or subliminally in the center of the visual field, before target presentation in the periphery. The task for participants was to localize the target as soon as possible. The reaction time needed to localize the target was consistently shorter for valid than invalid gaze cues for both types of gaze cues in both subliminal and supraliminal conditions. These findings indicate that attentional shift can be triggered even without awareness in response to another individual's eye gaze or head direction.

Involvement of medial temporal structures in reflexive attentional shift by gaze

Recent studies have revealed that eye gaze triggers reflexive shift of the observer's visuospatial attention to its direction even if it does not predict any events in the environment. To determine whether medial temporal structures are involved in this reflexive gaze processing, an experiment of the gaze-cuing paradigm was carried out in seven epileptic patients who had undergone unilateral temporal lobectomy and nine age- and IQ-matched epileptic controls who had not undergone any surgical treatments. Gaze cues were presented for 200 ms to the unilateral visual field, after which subjects were required to localize targets as quickly as possible. They were also instructed that gaze directions were not predictive of the location of the targets. When the gaze cues stimulated the intact hemisphere in lobectomized patients or either hemisphere in controls, reaction times for correct responses were significantly shorter when gaze directions were toward the targets than away from the targets. This cuing effect was not manifested following stimulation of the lesioned hemisphere in lobectomized patients. These findings suggest that the medial temporal structures, including the amygdala, play a crucial role in the reflexive shift of attention triggered by another person's gaze direction in humans.

Parietal disruption impairs reflexive spatial attention within and between sensory modalities

Reflexive spatial attention is critical for controlling perception and action. An established body of evidence suggests that mechanisms of spatial attention operate both within and between sensory modalities; however the attentional mechanisms that link modalities in the human brain are unclear. Here we used transcranial magnetic stimulation (TMS) to explore the role of the parietal cortex in coordinating reflexive shifts of spatial attention between vision and touch. In two experiments, healthy participants localised visual and somatosensory targets that were preceded by non-informative visual or somatosensory spatial cues. To determine the role of parietal cortex in spatial orienting, TMS was delivered synchronously with cue onset for 100ms. Results revealed a critical role of the right angular gyrus and supramarginal gyrus in reflexive orienting to visual and somatosensory targets that followed a somatosensory cue. In contrast, the same TMS protocol was ineffective in modulating reflexive orienting based on visual cues. This dependence on cue modality may reflect subcortical redundancy of visual orienting mechanisms. Overall, our results indicate a critical role of the inferior parietal cortex in mediating reflexive shifts of attention within and between sensory modalities.

Right hemispheric dominance in gaze-triggered reflexive shift of attention in humans

Recent findings suggest a right hemispheric dominance in gaze-triggered shifts of attention. The aim of this study was to clarify the dominant hemisphere in the gaze processing that mediates attentional shift. A target localization task, with preceding non-predicative gaze cues presented to each visual field, was undertaken by 44 healthy subjects, measuring reaction time (RT). A face identification task was also given to determine hemispheric dominance in face processing for each subject. RT differences between valid and invalid cues were larger when presented in the left rather than the right visual field. This held true regardless of individual hemispheric dominance in face processing. Together, these results indicate right hemispheric dominance in gaze-triggered reflexive shifts of attention in normal healthy subjects.

Spatial attention triggered by eye gaze enhances and speeds up visual processing in upper and lower visual fields beyond early striate visual processing

Objective The detection of a lateralized visual target is faster when preceded by a face gazing to the location of this stimulus. Here we aimed to clarify the time-course of the visual processing modulated by these reflexive shifts of attention. Methods ERPs were measured on 16 subjects performing a speeded location task on a circular checkerboard. The checkerboard target appeared either on the left or right of the upper or lower visual field, and was preceded by a central face orienting its gaze obliquely to one of the four possible corner locations for the target to appear. Results Congruently cued targets were located faster than incongruently cued targets and were associated with larger and earlier occipital P1 (∼110 ms) and occipito-parieto-temporal N1 (∼150 ms) components. However, no such attentional modulations were found on the earlier C1 visual component, best observed with a negative polarity for upper visual field stimulations, and thought to originate largely from primary visual cortex. Conclusions and significance These results show that reflexive shifts of attention following oblique eye gaze to upper and lower visual fields increase and speed up the processing of visual information beyond the feedforward flow of information in primary visual cortex.

Neural basis of auditory-induced shifts in visual time-order perception

Attended objects are perceived to occur before unattended objects even when the two objects are presented simultaneously. This finding has led to the widespread view that attention modulates the speed of neural transmission in the various perceptual pathways. We recorded event-related potentials during a time-order judgment task to determine whether a reflexive shift of attention to a sudden sound modulates the speed of sensory processing in the human visual system. Attentional cueing influenced the perceived order of lateralized visual events but not the timing of event-related potentials in visual cortex. Attentional cueing did, however, enhance the amplitude of neural activity in visual cortex, which shows that attention-induced shifts in visual time-order perception can arise from modulations of signal strength rather than processing speed in the early visual-cortical pathways.

Eye gaze does not produce reflexive shifts of attention: Evidence from frontal-lobe damage

Humans are able to predict the behavior of others using visual information. Several studies have argued that social cues, such as eye gaze direction, can influence the allocation of visual attention in a reflexive manner. We have previously shown that a patient with frontal-lobe damage, patient EVR, can use peripheral cues to direct attention but cannot use either word cues or gaze cues to allocate attention. These findings suggest that ‘social attention’ may involve frontal-lobe processes that control voluntary, not automatic, shifts of visuospatial attention. In the current paper, we further examine ‘social attention’ in EVR and demonstrate that his failure to orient attention voluntarily cannot be attributed to either cue predictability or a ‘sluggish’ attentional system. EVR exhibits a general impairment in orienting attention endogenously, and this impairment includes orienting from gaze cues. Gaze cues direct attention in a voluntary, not a reflexive, manner.

Sex differences in eye gaze and symbolic cueing of attention

Observing a face with averted eyes results in a reflexive shift of attention to the gazed-at location. Here we present results that show that this effect is weaker in males than in females (Experiment 1). This result is predicted by the 'extreme male brain' theory of autism (Baron-Cohen, 2003), which suggests that males in the normal population should display more autism-like traits than females (e.g., poor joint attention). Indeed, participants' scores on the Autism-Spectrum Quotient (Baron-Cohen, Wheelwright, Stott, Bolton, & Goodyear, 2001) negatively correlated with cueing magnitude. Furthermore, exogenous orienting did not differ between the sexes in two peripheral cueing experiments (Experiments 2a and 2b). However, a final experiment showed that using nonpredictive arrows instead of eyes as a central cue also revealed a large gender difference. This demonstrates that reduced orienting from central cues in males generalizes beyond gaze cues. These results show that while peripheral cueing is equivalent in the male and female brains, the attention systems of the two sexes treat noninformative symbolic cues very differently.

Gaze and arrow cueing of attention reveals individual differences along the autism spectrum as a function of target context

Observing averted gaze results in a reflexive shift of attention to the gazed-at location. In two experiments, participants scoring high and low on the Autism-Spectrum Quotient questionnaire (AQ; Baron-Cohen, Wheelwright, Skinner, Martin, & Clubley, 2001) observed arrow and gaze cues to investigate cueing effect magnitude as a function of the context in which peripheral targets could appear. While identical cueing effects were found with gaze and arrow cues, the more striking results concerned target stimuli. In Experiment 1, targets could appear on a peripheral face, or on scrambled face parts. Overall, greater cueing effects were found when the target appeared on a face. However, this face bias was only observed in participants with low AQ scores, whereas high AQ scorers oriented more to scrambled features. Experiment 2 found equal cueing to targets appearing on tools, as compared with tool parts. However, individual differences were again observed, where low AQ scorers showed larger cueing towards tools, while high scorers oriented more to scrambled parts, as in Experiment 1. These results support the idea that low AQ individuals orient strongly to objects attended by others. However, since the same results were found for arrow cues, this effect may generalize to all central cues to attention. High AQ scorers possessing many more autistic-like traits tended to orient more to scrambled shapes, perhaps reflecting a bias for orienting to local details.

VISUAL ORIENTING OCCURS ASYMMETRICALLY IN HORIZONTAL VS. VERTICAL PLANES

Recent behavioral data have shown that central gaze direction triggers reflexive shifts of attention to the cued location. Considering findings on the ecological adaptation of human vision, the authors expected that such a cueing effect would occur asymmetrically in horizontal and vertical planes. Participants detected a target letter appearing on a PC monitor after the brief presentation of a nonpredictive head­ cue (Experiment 1), profile head-cue (Experiment 2), or arrow-cue (Experiment 3) directed up, down, left, or right of fixation. In all experiments, a cueing effect was observed only when the cue was directed horizontally , but no significant effect was observed in the vertical plane. The results also showed that RTs to a target appearing horizontally were shorter than RTs to a target appearing verticall y, irrespective of the cue direction. These results might reflect humans' adaptation for extension of the visual field in the horizontal plane as a terrestrial primate species.

Perception of static eye gaze direction facilitates subsequent early visual processing.

Using event-related potentials (ERPs), it has been recently shown that a reflexive shift of attention following the observation of a dynamic eye gaze cue enhances and speeds up early visual processing of a target presented at the gazed-at location. Here we investigate whether similar early sensory modulations are also elicited by static gaze cues, or if previously described attentional effects were caused mainly by visual motion cues and not by eye gaze direction per se. Furthermore, we explore if these possible attentional orienting effects reflect facilitation of the processing of cued stimuli, inhibition of the unattended stimuli, or both. Subjects were presented with a face looking to the right or left visual field (VF), or straight away, before the occurrence of a lateralized target to detect. There were 3 conditions in this nonpredictive cueing task: (1) target presented in the VF indicated by the eye gaze direction (congruent); (2) opposite to the eye gaze direction (incongruent); or (3) preceded by a straight gazing face (neutral). Subjects were faster at detecting congruently than incongruently and neutrally cued targets. Facilitation effects were observed on early ERP components: the occipital P1 and occipito-temporal N1 components were speeded up as early as approximately 100 ms following stimulus onset (P1), and enhanced (P1 and N1) in response to congruent trials, particularly in the right hemisphere. Spatial attention triggered by static eye gaze direction produces response facilitations - predominantly lateralized to the right hemisphere - from the early sensory stages of visual processing. This study provides the first evidence of a speeding up and amplification of early visual processing following attention triggered by static eye gaze perception.

EFFECTS OF GAZE PERCEPTION ON RESPONSE TO LOCATION OR FEATURE

Some psychological studies have shown that changes in gaze direction trigger reflexive shifts of attention. The cortical region responding to eye gaze has connections with both of the two visual pathways responsible for spatial orientation and feature analysis. The purpose of the present study was to examine the effect of gaze-triggered attention on these two visual functions. Participants engaged in both location and orientation discrimination tasks with an uninformative gaze cue. The results indicate that the gaze direction of a schematic face facilitates responses only in the location discrimination task, and not in the orientation discrimination task. These results suggest a specific contribution of gaze perception to the processing of spatial orientation information. Moreover, further analysis of the data revealed that the compatibility between the gaze direction and the target location would be retained in implicit short-term memory.

Attention, Researchers! It Is Time to Take a Look at the Real World

Theories of attention, too often generated from artificial laboratory experiments, may have limited validity when attention in the natural world is considered. For instance, for more than two decades, conceptualizations of “reflexive” and “volitional” shifts of spatial attention have been grounded in methodologies that do not recognize or utilize the basic fact that people routinely use the eyes of other people as rich and complex attentional cues. This fact was confirmed by our novel discovery that eyes will trigger a reflexive shift of attention even when they are presented centrally and are known to be spatially nonpredictive. This exploration of real-world attention also led to our finding that, contrary to popular wisdom, arrows, like eyes, are capable of producing reflexive shifts of attention—a discovery that brings into question much of the existing attention research. We argue that research needs to be grounded in the real world and not in experimental paradigms. It is time for cognitive psychology to reaffirm the difficult task of studying attention in a manner that has relevance to real-life situations.

Anatomic dissociation of selective and suppressive processes in visual attention

Visual spatial attention is associated with activation in parietal regions as well as with modulation of visual activity in ventral occipital cortex. Within the parietal lobe, localisation of activity has been hampered by variation in individual anatomy. Using fMRI within regions of interest derived from individual functional maps, we examined the response of superior parietal lobule, intraparietal sulcus, and ventral occipital cortex in 11 normal adults as attention was directed to the left and right visual hemifields during bilateral visual stimulation. Activation in ventral occipital cortex was augmented contralateral to the attended hemifield ( P < 0.006), while intraparietal activation was augmented ipsilaterally ( P < 0.009), and superior parietal lobule showed no modulation of activity as a function of attended hemifield. These findings suggest that spatial enhancement of relevant stimuli in ventral occipital cortex is complemented by an intraparietal response associated with suppression of, or preparation of a reflexive shift of attention toward, irrelevant stimuli. The spatial attention system in superior parietal cortex, in contrast, may be driven to equal degrees by currently attended stimuli and by stimuli that are potential targets of attention.

EYE GAZE TRIGGERS VISUOSPATIAL ATTENTIONAL SHIFT IN INDIVIDUALS WITH AUTISM

We examined whether eye gaze triggers reflexive attentional shift in autism. First, autistic individuals who were lacking both joint attention behaviors and theory-ofmind abilities were examined. Targets were randomly presented to either the left or right side of a gazing face. Autistic subjects localized the targets faster when targets were congruent with than against gaze directions. The occurrence of this gazetriggered attentional shift was further examined using different stimulus onset asynchronies (SOAs) in autistic individuals and non-autistic controls. Autistic subjects similar to non-autistic controls responded faster when the targets were congruent with than against gaze directions for short SOA conditions. These results suggest that autistic individuals, even those lacking joint attention behaviors, respond reflexively to another person’s gaze directions.

Is pre‐attentive processing compromised by prolonged wakefulness? Effects of total sleep deprivation on the mismatch negativity

We investigated the potential influence of sustained wakefulness on pre-attentive capacities by recording the mismatch negativity (MMN), an electrophysiological manifestation associated with nonintentional detection of auditory oddball stimuli. The MMN was elicited by pitch deviants presented to both ears via earphones, at the beginning of a total sleep deprivation session (baseline), after 24 hr, and after 36 hr of continuous controlled wakefulness. A conspicuous MMN response was elicited at all three sessions. With time, however, a small yet significant gradual reduction in the MMN amplitude was evident. Whereas previous research suggested that controlled attention-demanding tasks are hampered by sleep deprivation, the balance of the present results suggests that passive (total) sleep deprivation may also bring about some degradation in the pre-attentive detection of environmental irregularities and as a consequence may disrupt the reflexive shift of attention induced by such events.

Spatial attention triggered by eye gaze increases and speeds up early visual activity.

What are the neuronal correlates of reflexive shifts of attention triggered by eye gaze direction? Event related potentials (ERPs) were measured on 14 subjects performing a spatial attention task where eye gaze direction of a face cued the location of a forthcoming target. Subjects were faster in detecting a validly cued target, i.e. one appearing at the location the eye was gazing at, compared to invalidly cued targets, despite the non-predictive value of the eye cues. ERP results showed an enhanced and earlier occipito-parietal P1 and N1 for valid trials, demonstrating the early modulation of visual input by attentional allocation. These findings provide the first evidence that social attention can rapidly modify the processing of visual information in extrastriate cortex.

Attracting attention to the illusory location of a sound: reflexive crossmodal orienting and ventriloquism.

Sound localization can be affected by vision; in the ventriloquism effect, sounds that are hard to localize within hearing become mislocalized toward the location of concurrent visual events. Here we tested whether spatial attention is drawn to the illusory location of a ventriloquized sound. The study exploited our previous finding that visual cues do not attract auditory attention. We report an important exception to this rule; auditory attention can be drawn to the location of a visual cue when it is paired with a concurrent unlocalizable sound, to produce ventriloquism. This demonstrates that crossmodal integration can precede reflexive shifts of attention, with such shifts taking place toward the crossmodally determined illusory location of a sound. It also shows that ventriloquism arises automatically, with objective as well as subjective consequences.

Deficient antisaccades in the social-emotional processing disorder.

We investigated whether adolescents and adults with the developmental social-emotional processing disorder (SEPD) exhibit deficits in visual attention, as measured by eye movements, when compared with dyslexic and normal control subjects. On the antisaccade task, subjects with SEPD made more errors than either control group and were the only group to show a decrease in performance accuracy compared with prosaccade. This deficit in inhibiting reflexive shifts of attention and gaze suggests that individuals with SEPD have dysfunction of the prefrontal component of the right hemisphere dominant network for spatially directed attention.