Exogenous and endogenous spatial attention effects on visuospatial working memory

In this study, we investigate how exogenous and endogenous orienting of spatial attention affect visuospatial working memory (VSWM). Specifically, we focused on two attentional effects and their consequences on storage in VSWM, when exogenous (Experiment 1) or endogenous (Experiment 2) orienting cues were used. The first effect, known as the meridian effect, is given by a decrement in behavioural performance when spatial cues and targets are presented in locations separated by vertical and/or horizontal meridians. The second effect, known as the distance effect, is given by a decrement in the orienting effects as a function of the spatial distance between cues and targets. Our results revealed a dissociation between exogenous and endogenous orienting mechanisms in terms of both meridian and distance effects. We found that meridian crossing affects performance only when endogenous cues were used. Specifically, VSWM performance with endogenous cueing depended more on the number of meridian crossings than on distance between cue and target. By contrast, a U-shaped distance dependency was observed using exogenous cues. Our findings therefore suggest that exogenous and endogenous orienting mechanisms lead to different forms of attentional bias for storage in VSWM.     

Attention and ageing: Measuring effects of involuntary and voluntary orienting in isolation and in combination

The cueing paradigm provides an established method for eliciting involuntary and voluntary attention shifts. Involuntary orienting is traditionally measured with non‐predictive peripheral cues and voluntary orienting with predictive central arrows. Recent studies with young adults have established that predictive central arrows trigger a combination of involuntary and voluntary orienting, raising the possibility that previous studies – including those with older adults – misinterpreted their findings with central arrow cues as isolating the effects of voluntary attention. The present experiment applied different cueing conditions that measured involuntary orienting, voluntary orienting, and involuntary and voluntary orienting in combination in older adults. The results show that past studies of voluntary orienting in older adults confound involuntary and voluntary orienting. Cueing effects in a condition that for the first time isolated voluntary orienting (predictive number cues) with older adults were significant, and comparable to effects for younger adults, demonstrating that older adults successfully utilize cues to direct their spatial attention strategically. A similar normal pattern of orienting was observed for involuntary orienting. Our study provides a methodology that can be applied effectively to isolate and investigate the effects of age on voluntary and involuntary attention.     

内源性注意与外源性注意的跨通道比较

该研究利用空间线索技术的实验模式,考察跨视觉和听觉通道的内源性选择注意与外源性选择性注意的相互关系。实验结果表明：(1)听觉中央线索在较长的SOA(至少500毫秒)条件下,可以引导内源性空间选择性注意;同时外周线索突现也能自动化地吸引部分注意资源。(2)听觉和视觉选择注意是分离的加工通道,但二者之间存在相互联系。     

Control of spatial orienting: Context-specific proportion cued effects in an exogenous spatial cueing task

Cognitive control refers to the ability to adjust strategy use based on the demands of a current context or task. Recent research using attentional filtering tasks has shown that cognitive control can adapt rapidly and automatically in accord with learning that is specific to particular tasks, items, and contexts (Crump, Gong, & Milliken, 2006; Fernandez-Duque & Knight, 2008; Jacoby, Lindsay, & Hessels, 2003). However, the role of context-specific control has not been investigated in detail in spatial orienting tasks. In a series of three experiments, the proportion of validly cued trials in an exogenous spatial cueing task was manipulated for one context but not for another context, with the two contexts intermixed randomly across trials. The results revealed that spatial/temporal contextual cues in conjunction, but not individually, produced context-specific control over spatial orienting.     

The neural correlates of social attention: automatic orienting to social and nonsocial cues

Previous evidence suggests that directional social cues (e.g., eye gaze) cause automatic shifts in attention toward gaze direction. It has been proposed that automatic attentional orienting driven by social cues (social orienting) involves a different neural network from automatic orienting driven by nonsocial cues. However, previous neuroimaging studies on social orienting have only compared gaze cues to symbolic cues, which typically engage top-down mechanisms. Therefore, we directly compared the neural activity involved in social orienting to that involved in purely automatic nonsocial orienting. Twenty participants performed a spatial cueing task consisting of social (gaze) cues and automatic nonsocial (peripheral squares) cues presented at short and long stimulus (cue-to-target) onset asynchronies (SOA), while undergoing fMRI. Behaviorally, a facilitation effect was found for both cue types at the short SOA, while an inhibitory effect (inhibition of return: IOR) was found only for nonsocial cues at the long SOA. Imaging results demonstrated that social and nonsocial cues recruited a largely overlapping fronto-parietal network. In addition, social cueing evoked greater activity in occipito-temporal regions at both SOAs, while nonsocial cueing recruited greater subcortical activity, but only for the long SOA (when IOR was found). A control experiment, including central arrow cues, confirmed that the occipito-temporal activity was at least in part due to the social nature of the cue and not simply to the location of presentation (central vs. peripheral). These results suggest an evolutionary trajectory for automatic orienting, from predominantly subcortical mechanisms for nonsocial orienting to predominantly cortical mechanisms for social orienting.     

Spatial Correspondence Learning is Critical for the Sequence Effects of Symbolic Cueing

Attention orienting has been found to be influenced by the previous cueing status in a spatial cueing paradigm. The purpose of this study was to determine whether the cue predictive values or the spatial correspondence learning between cues and targets could influence the sequence effect of symbolic cueing. The findings revealed that the predictive values of arrow or word cues do not lead to different sequence effects, but that visually asymmetrical letter cues, which allow spatial correspondence learning between cues and targets, induce stronger sequence effects than visually symmetrical letter cues. In addition, visually symmetrical directional word cues can induce sequence effects. The results suggest that spatial correspondence learning, although not obligatory, is critical for the sequence effects of symbolic cueing. The findings support the feature‐integration hypothesis, rather than the strategic adjustments account.     

Measuring effects of voluntary attention: A comparison among predictive arrow,colour, and number cues

The Posner cueing paradigm is one of the most widely used paradigms in attention research. Importantly, when employing it, it is critical to understand which type of orienting a cue triggers. It has been suggested that large effects elicited by predictive arrow cues reflect an interaction of involuntary and voluntary orienting. This conclusion is based on comparisons of cueing effects of predictive arrows, nonpredictive arrows (involuntary orienting), and predictive numbers (voluntary orienting). Experiment 1 investigated whether this conclusion is restricted to comparisons with number cues and showed similar results to those of previous studies, but now for comparisons to predictive colour cues, indicating that the earlier conclusion can be generalized. Experiment 2 assessed whether the size of a cueing effect is related to the ease of deriving direction information from a cue, based on the rationale that effects for arrows may be larger, because it may be easier to process direction information given by symbols such as arrows than that given by other cues. Indeed, direction information is derived faster and more accurately from arrows than from colour and number cues in a direction judgement task, and cueing effects are larger for arrows than for the other cues. Importantly though, performance in the two tasks is not correlated. Hence, the large cueing effects of arrows are not a result of the ease of information processing, but of the types of orienting that the arrows elicit.     

Responding to the direction of the eyes: In search of the masked gaze-cueing effect

Recent studies have demonstrated that masked gaze cues can produce a cueing effect. Those studies, however, all utilized a localization task and, hence, are ambiguous with respect to whether the previously observed masked gaze-cueing effect reflects the orienting of attention or the preparation of a motor response. The aim of the present study was to investigate this issue by determining whether masked gaze cues can modulate responses in detection and discrimination tasks, both of which isolate spatial attention from response priming. First, we found a gaze-cueing effect for unmasked cues in detection, discrimination, and localization tasks, which suggests that the gaze-cueing effect for visible cues is not task dependent. Second, and in contrast, we found a gaze-cueing effect for masked cues in a localization task, but not in detection or discrimination tasks, which suggests that the gaze-cueing effect for masked cues is task dependent. Therefore, the present study shows that the masked gaze-cueing effect is attributed to response priming, as opposed to the orienting of spatial attention.     

Inhibition of return in response to gaze cues: The roles of time course and fixation cue

Recent studies have demonstrated that orienting of attention in response to nonpredictive gaze cues arises rapidly and automatically, in a similar fashion to peripheral sudden onset cueing. However, while peripheral cues consistently elicit inhibition of return (IOR) at about 300 ms following cue onset, very little is known about inhibition effects in response to gaze cues. The present experiments systematically examined the conditions under which IOR arises with such cues. Reliable inhibition effects were obtained. Importantly, IOR emerged only at long cue-target intervals and only when a second cue actively triggered attention away from the cued location. This suggests that compared to sudden onset cueing, gaze cueing results in both prolonged facilitation and a delayed onset of inhibition processes. Thus, although both types of cues elicit very similar orienting effects in terms of their basic behavioural outcomes, there are more subtle differences between gaze and peripheral cues with respect to the maintenance and quality of those cueing effects across time.     

Resolving conflicting views: Gaze and arrow cues do not trigger rapid reflexive shifts of attention

It has become widely accepted that the direction of another individual's eye gaze induces rapid, automatic, attentional orienting, due to it being such a vital cue as to where in our environment we should attend. This automatic orienting has also been associated with the directional-arrow cues used in studies of spatial attention. Here, we present evidence that the response-time cueing effects reported for spatially nonpredictive gaze and arrow cues are not the result of rapid, automatic shifts of attention. For both cue types, response-time effects were observed only for long-duration cue and target stimuli that overlapped temporally, were largest when the cues were presented simultaneously with the response-relevant target, and were driven by a slowing of responses for invalidly cued targets rather than speeding for validly cued ones. These results argue against automatic attention-orienting accounts and support a novel spatial-incongruency explanation for a whole class of rapid behavioural cueing effects.     

Attention to arrows: Pointing to a new direction

It was long believed that central arrows needed to be spatially predictive to produce a shift in spatial attention. Recent evidence indicates, however, that central spatially nonpredictive directional cues, like arrows, will trigger reflexive shifts in attention. We asked what this recent discovery means for past studies that used predictive directional cues such as arrows. Our findings indicate that predictive arrows produce attention effects that greatly exceed the individual or summed effects of reflexive orienting to nonpredictive arrows and volitional orienting to predictive numbers. This suggests that the especially large effect produced by predictive arrows reflects an interaction between reflexive and volitional orienting. Given the broad application of the predictive arrow cueing paradigm in both past and current research, the present data shed new light on a wide range of investigations, from psychophysical studies of basic attention to behavioural and neuroimaging studies of cognition and social development.     

Attention to arrows: pointing to a new direction

It was long believed that central arrows needed to be spatially predictive to produce a shift in spatial attention. Recent evidence indicates, however, that central spatially nonpredictive directional cues, like arrows, will trigger reflexive shifts in attention. We asked what this recent discovery means for past studies that used predictive directional cues such as arrows. Our findings indicate that predictive arrows produce attention effects that greatly exceed the individual or summed effects of reflexive orienting to nonpredictive arrows and volitional orienting to predictive numbers. This suggests that the especially large effect produced by predictive arrows reflects an interaction between reflexive and volitional orienting. Given the broad application of the predictive arrow cueing paradigm in both past and current research, the present data shed new light on a wide range of investigations, from psychophysical studies of basic attention to behavioural and neuroimaging studies of cognition and social development.     

How does reward compete with goal-directed and stimulus-driven shifts of attention?

In order to behave adaptively, attention can be directed in space either voluntarily (i.e. endogenously) according to strategic goals, or involuntarily (i.e. exogenously) through reflexive capture by salient or novel events. The emotional or motivational values of stimuli can also influence attentional orienting. However, little is known about how reward-related effects compete or interact with endogenous and exogenous attention mechanisms. Here we designed a visual search paradigm in which goal-driven and stimulus-driven shifts of attention were manipulated by classic spatial cueing procedures, while an irrelevant, but previously rewarded stimulus also appeared as a distractor and hence competed with both types of spatial attention during search. Our results demonstrated that stimuli previously associated with a high monetary reward received higher attentional priority in the subsequent visual search task, even though these stimuli and reward were no longer task-relevant, mitigating the attentional orienting induced by both endogenous and exogenous cues.     

Attentional asymmetries in a visual orienting task are related to temperament

Spatial asymmetries are an intriguing feature of directed attention. Recent observations indicate an influence of temperament upon the direction of these asymmetries. It is unknown whether this influence generalises to visual orienting behaviour. The aim of the current study was therefore to explore the relationship between temperament and measures of spatial orienting as a function of target hemifield. An exogenous cueing task was administered to 92 healthy participants. Temperament was assessed using Carver and White's (1994) Behavioural Inhibition System and Behavioural Activation System (BIS/BAS) scales. Individuals with high sensitivity to punishment and low sensitivity to reward showed a leftward asymmetry of directed attention when there was no informative spatial cue provided. This asymmetry was not present when targets were preceded by spatial cues that were either valid or invalid. The findings support the notion that individual variations in temperament influence spatial asymmetries in visual orienting, but only when lateral targets are preceded by a non-directional (neutral) cue. The results are discussed in terms of hemispheric asymmetries and dopamine activity.     

The role of the oculomotor system in covert social attention

Observing a change in gaze direction triggers a reflexive shift of attention and appears to engage the eye-movement system. However, the functional relationship between social attention and this oculomotor activation is unclear. One extremely influential hypothesis is that the preparation of a saccadic eye movement is necessary and sufficient for a covert, reflexive shift of attention (the premotor theory of attention; Rizzolatti et al., 1994). Surprisingly, this theory has not been directly tested with respect to reflexive gaze cueing. In order to address this issue, gaze cueing, peripheral cueing, and arrow cueing were examined under conditions in which some stimuli appeared at locations that could not become the goal of a saccadic eye movement. It was observed that peripheral cues failed to elicit reflexive attentional orienting when targets appeared beyond the range of eye movements. Similarly, nonpredictive arrow cues were ineffective when targets could not become the goal of a saccade. In contrast, significant gaze-cueing effects were still observed when targets were beyond the range of eye movements. These data demonstrate that the mechanisms involved in gaze cueing are dissociated from those involved in exogenous orienting to peripheral or arrow cues. Furthermore, the findings suggest that, unlike peripheral cueing and reflexive arrow cueing, gaze cueing is independent of oculomotor control. We conclude that the premotor theory does not offer a compelling explanation for gaze cueing.     

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.     

Covert orienting to the locations of targets and distractors: Effects on response channel activation in a flanker task

The role of covert orienting of attention in response channel activation was examined using the flanker interference and precueing paradigms. Four experiments assessed the influence of distractors on the discrimination of a target colour patch under cueing conditions (three with non-informative, exogenous cues and one with informative, endogenous cues) that modulated attention at the flanker or target locations. Across all of the experiments, the amount of interference generated by the distractors was not modulated by the facilitation and inhibition of return induced by spatial attention precues. These results are consistent with previous reports of patients with neglect, which demonstrated that flanker interference proceeds at unattended locations (Audet, Bub, & Lecours, 1991; Cohen, Ivry, Rafal, & Kohn, 1995), and they suggest that response channel activation can occur independently from spatial attention.     

Masked stimuli modulate endogenous shifts of spatial attention

Unconscious stimuli can influence participants’ motor behavior but also more complex mental processes. Recent research has gradually extended the limits of effects of unconscious stimuli. One field of research where such limits have been proposed is spatial cueing, where exogenous automatic shifts of attention have been distinguished from endogenous controlled processes which govern voluntary shifts of attention. Previous evidence suggests unconscious effects on mechanisms of exogenous shifts of attention. Here, we applied a cue-priming paradigm to a spatial cueing task with arbitrary cues by centrally presenting a masked symmetrical prime before every cue stimulus. We found priming effects on response times in target discrimination tasks with the typical dynamic of cue-priming effects (Experiments 1 and 2) indicating that central symmetrical stimuli which have been associated with endogenous orienting can modulate shifts of spatial attention even when they are masked. Prime–Cue Congruency effects of perceptual dissimilar prime and cue stimuli (Experiment 3) suggest that these effects cannot be entirely reduced to perceptual repetition priming of cue processing. In addition, priming effects did not differ between participants with good and poor prime recognition performance consistent with the view that unconscious stimulus features have access to processes of endogenous shifts of attention.     

Electrophysiological modulations of exogenous attention by intervening events

The present study used event related potentials (ERPs) in a spatial cueing procedure to investigate the stages of processing influenced by intervening events presented between cues and targets, when they produce maximal behavioural modulations (i.e., facilitation in the absence of the intervening event, and inhibition of return – IOR, when the intervening event is presented). Our data challenge the traditional orienting–reorienting hypothesis, leading to alternative explanations of cueing effects that are beyond the orienting of attention. Peripheral cues always produced a detection cost (reflected in a reduced amplitude of the P100 component for cued as compared to uncued trials), independently on the behavioural effect that was measured. In contrast, facilitation was associated to modulations of later-stage components, such as N100, Nd, and P300. The N2pc component, usually associated to spatial selection, was the only component reflecting opposite and significant modulations associated to the behavioural effect. The present results suggest that facilitation and IOR can arise from changes at different stages of processing. We propose that the perceptual detection cost (reflected on the P100), and the hindered spatial selection (reflected on the N2pc) at the cued location determine the IOR effect at least in discrimination tasks, while the contribution of the later-stage components, beside attentional processes, determines other facilitatory effects of cueing, which altogether determine the behavioural effect that is measured.     

Problems inhibiting attentional capture by irrelevant stimuli in patients with frontotemporal dementia

We studied the role of the frontal lobes in orienting spatial attention and inhibiting attentional capture by goal-irrelevant stimuli, using a spatial cueing method in patients with frontotemporal dementia (FTD). Two blocks of trials were presented, one with non-predictive cues and the other with counter-predictive cues. FTD patients showed a global orienting deficit, with a greater difference between invalid and valid trials than age-matched controls. However, they were able to use the (counter-) predictiveness of the cue to reduce the invalid/valid difference when targets occurred most often in the location opposite the cue. Thus, endogenous control of attention in our FTD patients was sufficient to reorient attention on the basis of the probability of events, but not to resist the capture of attention by goal-irrelevant stimuli. These results confirm the role of frontal lobes in the inhibition of attentional capture.