Uncued Locations Research Articles

Visible propagation from invisible exogenous cueing

Perception and performance is affected not just by what we see but also by what we do not see-inputs that escape our awareness. While conscious processing and unconscious processing have been assumed to be separate and independent, here we report the propagation of unconscious exogenous cueing as determined by conscious motion perception. In a paradigm combining masked exogenous cueing and apparent motion, we show that, when an onset cue was rendered invisible, the unconscious exogenous cueing effect traveled, manifesting at uncued locations (4° apart) in accordance with conscious perception of visual motion; the effect diminished when the cue-to-target distance was 8° apart. In contrast, conscious exogenous cueing manifested in both distances. Further evidence reveals that the unconscious and conscious nonretinotopic effects could not be explained by an attentional gradient, nor by bottom-up, energy-based motion mechanisms, but rather they were subserved by top-down, tracking-based motion mechanisms. We thus term these effects mobile cueing. Taken together, unconscious mobile cueing effects (a) demonstrate a previously unknown degree of flexibility of unconscious exogenous attention; (b) embody a simultaneous dissociation and association of attention and consciousness, in which exogenous attention can occur without cue awareness ("dissociation"), yet at the same time its effect is contingent on conscious motion tracking ("association"); and (c) underscore the interaction of conscious and unconscious processing, providing evidence for an unconscious effect that is not automatic but controlled.

Textures shape the attentional focus: Evidence from exogenous and endogenous cueing

The spatial cueing paradigm (Posner Quarterly Journal of Experimental Psychology 32:3-25, 1980) has often been used to investigate the time course of the deployment of visual attention in space. In a series of eight experiments we investigated whether spatial cues would not only enhance processing of stimuli presented at cued locations, but also enhance processing of the entire texture in which the stimuli were presented. Results showed highest accuracy for responses to stimuli presented at cued locations, a replication of the traditional cueing effect (Posner 1980). Additionally, stimuli presented at uncued locations were responded to with higher accuracy when they were presented inside the same texture as the cued location, as compared with stimuli presented outside the texture with the cued location. To investigate this texture advantage for both automatic and voluntary attention deployment, exogenous and endogenous cues were used. The texture advantage was observed for short interstimulus intervals (ISIs) of 50 and 100 ms for exogenous cues and for a longer ISI of 200 ms for endogenous cues. These findings indicate that the arrangement of task-irrelevant visual stimuli also can have a large impact on the cueing effect. This suggests that visual spatial attention spreads texture-wise across the visual field. Control experiments revealed that the homogeneity within texture elements contributes most to the effect but that the texture advantage is a function of both orientation contrast at the texture border and homogeneity within texture elements.

Inhibition of return to emotional faces

Inhibition of Return (IOR) refers to a phenomenon that reaction times are slowed to a target that appears at a previously attended location. To investigate whether the mechanism of IOR is modulated by emotional contents of stimuli, the current study examined IOR to angry, happy and neutral faces. The speed-accuracy trade-off (SAT) function was measured to assess IOR in terms of sensitivity and processing time related to targets. Participants were required to discriminate gender of faces presenting on the cued or uncued locations under various response speeds controlled by experimenter. We have three findings: Firstly IOR to neutral faces was associated with shifts in response criterion, in line with our previous findings (Zhao et al. 2011). Secondly, IOR to emotional (angry and happy) faces was evident only at an early stage of target processing. Moreover, it was eliminated at a later stage of target processing and was reversed into a facilitation effect. According to the evolutional view, the arousal state decreased the response criterion to emotional faces which are interesting and important to us. Finally, perceptual sensitivity of gender discrimination was decreased to angry compared to neutral faces and the levels of decrement were significantly correlated to participants’ state-trait anxiety. Negative stimuli may increase the attentional demand as they might threat our chance of survival. This may lead to less attentional resource available for the discrimination task and in turn performance was impaired. In conclusion, the findings extended the evidence of IOR reflecting a criterion shift from low-level signal (e.g. ‘+’ or ‘x’) to high-level socially relevant stimuli such as neutral faces. Furthermore, it suggests that the arousing dimension of emotion interacted IOR in the response level while the valence dimension of emotion affected discrimination in the attentional level. Meeting abstract presented at VSS 2013

Blocking the Link between Stimulus and Response at Previously Attended Locations: Evidence for Inhibitory Tagging Mechanism

Inhibition of return (IOR) refers to a slower response to a target appearing at the previously attended location (also called the cued location) than to a target appearing at an unattended location (uncued location). Inhibitory tagging (IT) involving the attentional executive network is suggested to function by blocking or disconnecting the link between a stimulus representation and the corresponding response mapping at the cued location. Data from behavioral and neuroscience studies are integrated to discuss the IT theory. Behaviorally, the IT effect can be measured by the comparisons of the priming or conflict effects at the cued location versus effects at the uncued location. It has been suggested that IT can reduce or even eliminate the priming effect in semantic priming tasks and the conflict effect in the Stroop (either color-word or spatial Stroop) and the Flanker interference tasks at previously attended locations. Neural correlates of IT are also summarized. Specifically, the posterior parietal lobe, the anterior cingulate cortex (ACC), and the prefrontal cortex (PFC) are suggested to be involved in IT. Reduced event-related potentials (ERPs) components at the cued location provided evidences for IT; these included the N450 component, which is related to conflict resolution processing, and the N400 component, which is related to semantic priming processing, Finally, some comments and prospective remarks on IT are given. Keywords: Attentional network, inhibition of return (IOR), inhibitory tagging (IT), spatial cueing procedure, stimulus-response link.

Rethinking human visual attention: Spatial cueing effects and optimality of decisions by honeybees, monkeys and humans

Visual attention is commonly studied by using visuo-spatial cues indicating probable locations of a target and assessing the effect of the validity of the cue on perceptual performance and its neural correlates. Here, we adapt a cueing task to measure spatial cueing effects on the decisions of honeybees and compare their behavior to that of humans and monkeys in a similarly structured two-alternative forced-choice perceptual task. Unlike the typical cueing paradigm in which the stimulus strength remains unchanged within a block of trials, for the monkey and human studies we randomized the contrast of the signal to simulate more real world conditions in which the organism is uncertain about the strength of the signal. A Bayesian ideal observer that weights sensory evidence from cued and uncued locations based on the cue validity to maximize overall performance is used as a benchmark of comparison against the three animals and other suboptimal models: probability matching, ignore the cue, always follow the cue, and an additive bias/single decision threshold model. We find that the cueing effect is pervasive across all three species but is smaller in size than that shown by the Bayesian ideal observer. Humans show a larger cueing effect than monkeys and bees show the smallest effect. The cueing effect and overall performance of the honeybees allows rejection of the models in which the bees are ignoring the cue, following the cue and disregarding stimuli to be discriminated, or adopting a probability matching strategy. Stimulus strength uncertainty also reduces the theoretically predicted variation in cueing effect with stimulus strength of an optimal Bayesian observer and diminishes the size of the cueing effect when stimulus strength is low. A more biologically plausible model that includes an additive bias to the sensory response from the cued location, although not mathematically equivalent to the optimal observer for the case stimulus strength uncertainty, can approximate the benefits of the more computationally complex optimal Bayesian model. We discuss the implications of our findings on the field's common conceptualization of covert visual attention in the cueing task and what aspects, if any, might be unique to humans.

Implicit learning of spatiotemporal contingencies in spatial cueing.

We investigated the role of implicit spatiotemporal learning in the Posner spatial cueing of attention task. During initial training, the proportion of different trial types was altered to produce a complex pattern of spatiotemporal contingencies between cues and targets. For example, in the short invalid and long valid condition, targets reliably appeared either at an uncued location after a short stimulus onset asynchrony (SOA; 100 ms) or at a cued location after a long SOA (350 ms). As revealed by postexperiment questioning, most participants were unaware of these manipulations. Whereas prior studies have examined reaction times during training, the current study examined the long-term effect of training on subsequent testing that removed these contingencies. An initial experiment found training effects only for the long SOAs that typically produce inhibition of return (IOR) effects. For instance, after short invalid and long valid training, there was a benefit at long SOAs rather than an IOR effect. A 2nd experiment ruled out target-cue overlap as an explanation of the difference between learning for long versus short SOAs. Rather than a mix of perfectly predictable spatiotemporal contingencies, Experiment 3 used only short SOA trials during training with a probabilistic spatial contingency. There was a smaller but reliable training effect in subsequent testing. These results demonstrate that implicit learning for specific combinations of location and SOA can affect behavior in spatial cueing paradigms, which is a necessary result if more generally spatial cueing reflects learned spatiotemporal regularities.

Behavioral and neural interaction between spatial inhibition of return and the Simon effect

It has been well documented that the anatomically independent attention networks in the human brain interact functionally to achieve goal-directed behaviors. By combining spatial inhibition of return (IOR) which implicates the orienting network with some executive function tasks (e.g., the Stroop and the flanker tasks) which implicate the executive network, researchers consistently found that the interference effects are significantly reduced at cued compared to uncued locations, indicating the functional interaction between the two attention networks. However, a unique, but consistent effect is observed when spatial IOR is combined with the Simon effect: the Simon effect is significantly larger at the cued than uncued locations. To investigate the neural substrates underlying this phenomenon, we orthogonally combined the spatial IOR with the Simon effect in the present event-related fMRI study. Our behavioral data replicated previous results by showing larger Simon effect at the cued location. At the neural level, we found shared spatial representation system between spatial IOR and the Simon effect in bilateral posterior parietal cortex (PPC); spatial IOR specifically activated bilateral superior parietal cortex while the Simon effect specifically activated bilateral middle frontal cortex. Moreover, left precentral gyrus was involved in the neural interaction between spatial IOR and the Simon effect by showing significantly higher neural activity in the “Cued_Congruent” condition. Taken together, our results suggest that due to the shared spatial representation system in the PPC, responses were significantly facilitated when spatial IOR and the Simon effect relied on the same spatial representations, i.e., in the “Cued_Congruent” condition. Correspondingly, the sensorimotor system was significantly involved in the “Cued_Congruent” condition to fasten the responses, which indirectly resulted in the enhanced Simon effect at the cued location.

Complementary attentional components of successful memory encoding

Attention during encoding improves later memory, but how this happens is poorly understood. To investigate the role of attention in memory formation, we combined a variant of a spatial attention cuing task with a subsequent memory fMRI design. Scene stimuli were presented in the periphery to either the left or right of fixation, preceded by a central face cue whose gaze oriented attention to the probable location of the scene. We contrasted activity for scenes appearing in cued versus uncued locations to identify: (1) regions where cuing facilitated processing, and (2) regions involved in reorienting. We then tested how activity in these facilitation and reorienting regions of interest predicted subsequent long-term memory for individual scenes. In facilitation regions such as parahippocampal cortex, greater activity during encoding predicted memory success. In reorienting regions such as right temporoparietal junction, greater activity during encoding predicted memory failure. We interpret these results as evidence that memory formation benefits from attentional facilitation of perceptual processing combined with suppression of the ventral attention network to prevent reorienting to distractors.

Dissociable Spatial and Temporal Effects of Inhibition of Return

Inhibition of return (IOR) refers to the relative suppression of processing at locations that have recently been attended. It is frequently explored using a spatial cueing paradigm and is characterized by slower responses to cued than to uncued locations. The current study investigates the impact of IOR on overt visual orienting involving saccadic eye movements. Using a spatial cueing paradigm, our experiments have demonstrated that at a cue-target onset asynchrony (CTOA) of 400 ms saccades to the vicinity of cued locations are not only delayed (temporal cost) but also biased away (spatial effect). Both of these effects are basically no longer present at a CTOA of 1200 ms. At a shorter 200 ms CTOA, the spatial effect becomes stronger while the temporal cost is replaced by a temporal benefit. These findings suggest that IOR has a spatial effect that is dissociable from its temporal effect. Simulations using a neural field model of the superior colliculus (SC) revealed that a theory relying on short-term depression (STD) of the input pathway can explain most, but not all, temporal and spatial effects of IOR.

The head turn cueing effect is sustained at longer SOA's in the presence of an object distractor

In social cueing studies, participants are asked to discriminate a target object cued by social signals, such as eye gaze or head turns. Knowing that the cues are not predictive, participants nevertheless respond faster to the target presented at the cued than uncued location at short Stimulus Onset Asynchrony (SOA) intervals of 300 to 600 ms. However, as the SOA between the cue and target increases (1005 ms), the cueing effect diminishes indicating that the reflexivity of social cues can be overridden by voluntary, controlled processes.In the current study, we tested the reflexive and voluntary characteristics of social cues in an object recognition task. In our paradigm, participants were asked to discriminate a circle or square target object appearing in the left or right hand of a human model. On half of the trials, a distractor triangle object appeared in the opposite hand and on the other half of the trials, no distractor object was presented in the opposite hand. The target object was cued by a head turn that appeared at SOA's of 0, 105, 300, 600 or 1005 ms. Participants had to report which target they saw by key press and were told to ignore the head turn because it had no predictive validity. Without a distractor, the typical results were found where a cueing effect was evident at SOAs of 300 and 600 ms and disappeared at the longer 1005 ms SOA. However, in the distractor present condition, a cueing effect was found at the 300, 600 and critically, remained potent at the SOA of 1005 ms. These results call into the question of the reflexive-voluntary account of social cueing effect and suggest that, in the presence of a distractor object, head turn cues cannot be voluntarily inhibited at the long SOA. Meeting abstract presented at VSS 2012

Spatial eccentricity and temporal transition of split attentional foci

Various investigations have demonstrated that attentional focus is unitary, not splitable, over contiguous regions of space. However, others find that observers can split attentional foci concurrently over noncontiguous regions concurrently (e.g., Awh & Pashler, 2000). Key differences among studies remain unclear. We manipulated the spatial eccentricity of targets and explored temporal transition of attentional foci using Awh and Pashler’s (2000) partial report procedure. We also tested whether individual differences in working memory capacity affect the style of deploying attentional foci. Literature shows that individuals with high working memory capacity were able to simultaneously allocate their attention to noncontiguous regions. This leads to the prediction that working memory capacity contributes to differences in the style of deployment of attentional focus/foci. In the present study, prior to the onset of a search display consisted of nontargets (letters) and two targets (digits), two cues appeared at noncontiguous locations either horizontally or vertically. These cues indicated target locations in 80% of the trials. Cues and targets were separated by an SOA (50ms or 750ms) to probe the development of an attentional split, if any, over time. Results demonstrated a split of attention: target identification accuracy was higher at noncontiguous locations relative to those at the intervening uncued locations. This is consistent with results of Awh and Pasher (2000), with the exception that no cueing effect was obtained with vertical cues for short SOAs (50ms). No effect of working memory capacity was found on the split of attention. These results suggest that attentional split develops over time and space regardless of individual differences in working memory capacity. Meeting abstract presented at VSS 2012

Temporary inhibitory tagging at previously attended locations: Evidence from event‐related potentials

Recent studies propose that a mechanism termed "inhibitory tagging" acts upon the processing of the target at the attended location by temporarily blocking the stimulus-response mapping. Here we combined the cue-target paradigm with the Stroop task and measured event-related potential (ERP) responses to the color of a color word presented at the previously attended (cued) or unattended (uncued) location. We found that the conflict-related N450 effect emerged later and had a smaller size at the cued than the uncued location. The overall ERP responses to the target showed lower P1 and N1 amplitude at the cued than the uncued location. Although the P1/N1 effect may reflect deficient perceptual processing of the target, the delay of the N450 suggests that the link between perceptual processing and response activation is temporarily blocked at the previously attended location.

Electrophysiological evidence for inhibition of return effect in exogenous orienting

Although the inhibition of return (IOR) effect in exogenous orienting has been investigated extensively with the Posnerian cuing paradigm, there has been little evidence for the role of attentional processes in the IOR effect. The N2pc component was used as a marker of the deployment of spatial attention to isolate attentional processes in the IOR effect. Participants responded to task-relevant target displays that were preceded by cue displays in a non-predictive, exogenous cuing paradigm. A 1,000ms of stimulus onset asynchrony (SOA) was designed to investigate the IOR effect. Behavioral results indicate that the SOA was sufficiently long to cause an IOR effect in the discrimination task. As for ERP patterns elicited by targets, the N2pc amplitudes were similar across cue types, but the N2pc latency was delayed when targets appeared at the cued location rather than at the uncued location. N2pc patterns demonstrated that the spatial attentional process is indeed an important mechanism underlying the IOR effect. The delayed N2pc for targets in the valid cue type suggested that IOR effect may reflect a delayed deployment of spatial attention to targets appearing at recently cued locations.

Attentional Modulations Related to Spatial Gating but Not to Allocation of Limited Resources in Primate V1

Attention can modulate neural responses in sensory cortical areas and improve behavioral performance in perceptual tasks. However, the nature and purpose of these modulations remain under debate. Here weused voltage-sensitive dye imaging (VSDI) to measure V1 population responses while monkeys performed a difficult detection task under focal or distributed attention. We found that V1 responses at attended locations are significantly elevated relative to actively ignored or irrelevant locations, consistent with the hypothesis that an important goal of attention in V1 is to highlight task-relevant information. Surprisingly, these modulations were indistinguishable under focal and distributed attention, suggesting a minor or no role for attention as a mechanism for allocating limited representational resources in V1. The response elevation at attended locations is additive, is widespread, and starts shortly before stimulus onset. This elevation could contribute to spatial gating by biasing competition in subsequent processing stages in favor of attended stimuli.

Inhibition of return: A “depth-blind” mechanism?

When attention is oriented to a peripheral visual event, observers respond faster to stimuli presented at a cued location than at an uncued location. Following initial reaction time facilitation responses are slower to stimuli subsequently displayed at the cued location, an effect known as inhibition of return (IOR). Both facilitatory and inhibitory effects have been extensively investigated in two-dimensional space. Facilitation has also been documented in three-dimensional space, however the presence of IOR in 3D space is unclear, possibly because IOR has not been evaluated in an empty 3D space. Determining if IOR is sensitive to the depth plane of stimuli or if only their bi-dimensional location is inhibited may clarify the nature of the IOR. To address this issue, we used an attentional cueing paradigm in three-dimensional (3D) space. Results were obtained from fourteen participants showed IOR components in 3D space when binocular disparity was used to induce depth. We conclude that attentional orienting in depth operates as efficiently as in the bi-dimensional space.

Visuospatial attention in schizophrenia: Deficits in broad monitoring.

Although selective attention is thought to be impaired in people with schizophrenia (PSZ), prior research has found no deficit in the ability to select one location and withdraw attention from another. PSZ and healthy control subjects (HCS) performed a stimulus detection task in which one, two, or all four peripheral target locations were cued. When one or two locations were cued, both PSZ and HCS responded faster when the target appeared at a cued than uncued location. However, increases in the number of validly cued locations had much more deleterious effects on performance for PSZ than HCS, especially for targets of low contrast whose detection was more dependent on attention. PSZ also responded more slowly in trials with four cued locations relative to trials with one or two invalidly cued locations. Thus, visuospatial attention deficits in schizophrenia arise when broad monitoring is required rather than when attention must be focused narrowly.

Object-based control of attention is sensitive to recent experience.

How is attention guided by past experience? In visual search, numerous studies have shown that recent trials influence responses to the current trial. Repeating features such as color, shape, or location of a target facilitates performance. Here we examine whether recent experience also modulates a more abstract dimension of attentional control, object-based and location-based control. Participants performed a cued target discrimination task with stimuli presented on 2 rectangles. Response times to targets appearing in an uncued location on a cued rectangle were faster than to targets on the uncued rectangle, demonstrating an object-based attentional benefit. We investigated the object-based benefit on the current trial contingent on the cue-target relationship on the previous trial. The object-based benefit was significant only when the cued object contained the target on the previous trial, not when the uncued object contained the target. This effect of recent experience was not due to either the repetition of spatial cue-target location or the repetition of the response, but to adaptation to contingencies in the environment. Our results suggest a unifying view of attentional control that spans the concrete dimensions of control (e.g., determining the relative importance of red vs. blue) to the abstract (determining the relative importance of objects vs. locations in space). Attention closely tracks the short time scale structure of the environment and automatically adapts to optimize performance to this structure.

Early dissociation between neural signatures of endogenous spatial attention and perceptual awareness during visual masking

The relationship between spatial attention and conscious access has often been pictured as a single causal link: spatial attention would provide conscious access to weak stimuli by increasing their effective contrast during early visual processing. To test this hypothesis, we assessed whether the early attentional amplification of visual responses, around 100 ms following stimulus onset, had a decisive impact on conscious detection. We recorded magnetoencephalographic (MEG) signals while participants focused their attention toward or away from masked stimuli which were physically identical but consciously detected half of the time. Spatial attention increased the amplitude of early occipital responses identically for both detected and missed stimuli around 100 ms, and therefore, did not control conscious access. Accordingly, spatial attention did not increase the proportion of detected stimuli. The earliest neuromagnetic correlate of conscious detection, around 120 ms over the contralateral temporal cortex, was independent from the locus of attention. This early activation combined objective information about stimulus presence and subjective information about stimulus visibility, and was followed by a late correlate of conscious reportability, from 220 ms over temporal and frontal cortex, which correlated exclusively with stimulus visibility. This widespread activation coincided in time with the reorienting of attention triggered by masks presented at the uncued location. This reorienting was stronger and occurred earlier when the masked stimulus was detected, suggesting that the conscious detection of a masked stimulus at an unexpected location captures spatial attention. Altogether, these results support a double dissociation between the neural signatures of endogenous spatial attention and perceptual awareness.

Subliminal stimuli in the near absence of attention influence top-down cognitive control

Recent research has shown that visual stimuli can influence cognitive control functions, even if subjects are unaware of the identity of the stimuli. However, in those previous studies, subjects actively attended to the location of the subliminal stimuli. Here we assessed the role of endogenous spatial attention in such paradigms. We required subjects to quickly prepare for one of two numerical judgment tasks on the basis of the direction of motion in patches of moving dots presented in cued spatial locations. We found that irrelevant motion patches presented in the uncued spatial locations also influenced task performance. Motion in the uncued patches was weak and did not affect the perception of the cued patches. Further analyses suggested that the effect of priming by the uncued stimuli was present even for subjects who could only discriminate such stimuli at chance level. Three additional experiments confirmed that subjects paid minimal attention to the uncued locations, in that the subjects could not perform simple discriminations of conjunctions of features in those locations.

Reflexive attention in touch: An investigation of event related potentials and behavioural responses

Exogenous attention has been extensively studied in vision but little is known about its behavioural and neural correlates in touch. To investigate this, non-informative tactile cues were followed after 800ms by tactile targets and participants either detected targets or discriminated their location. Responses were slowed for targets at cued compared to uncued locations (i.e. inhibition of return (IOR)) only in the detection task. Concurrently recorded ERPs showed enhanced negativity for targets at uncued compared to cued locations at the N80 component and this modulation overlapped with the P100 component but only for the detection task indicating IOR may, if anything, be linked to attentional modulations at the P100. Further, cue-target interval analysis showed an enhanced anterior negativity contralateral to the cue side in both tasks, analogous to the anterior directed attention negativity (ADAN) previously only reported during endogenous orienting.