The relationship between inhibition of return and saccade trajectory deviations

After presentation of a peripheral cue, a subsequent saccade to the cued location is delayed (inhibition of return: IOR). Furthermore, saccades typically deviate away from the cued location. The present study examined the relationship between these inhibitory effects. IOR and saccade trajectory deviations were found after central (endogenous) and peripheral (exogenous) cuing of attention, and both effects were larger with an onset cue than with a color singleton cue. However, a dissociation in time course was found between IOR and saccade trajectory deviations. Saccade trajectory deviations occurred at short delays between the cue and the saccade, but IOR was found at longer delays. A model is proposed in which IOR is caused by inhibition applied to a preoculomotor attentional map, whereas saccade trajectory deviations are caused by inhibition applied to the saccade map, in which the final stage of oculomotor programming takes place.     

The role of temporal and spatial factors in the covert orienting of visual attention tasks

There is a biphasic pattern in response times to peripheral uninformative cues, with faster responses to targets in cued locations when the stimulus onset asynchrony (SOA) is under 300 ms and slower responses when it is over 300 ms. The effect has typically been attributed entirely to the SOA while ignoring other aspects of the cues (duration, spatial configuration). To examine these other factors, along with SOA, the present experiments included manipulations of SOA (50, 100, 200, 400, 800 ms), inter-stimulus interval (ISI; 0, 50, 100, 150, 200, 300, 350, 400, 500, 600, 700, and 750 ms), and whether or not the cue and target overlap in the same space. The results indicate that cueing effects depend on the combination of cue duration, ISI, SOA, and the spatial configuration of the cues and targets. Three factors are used to explain these time course results.     

Predictive remapping gives rise to environmental inhibition of return

Neurons in various brain regions predictively respond to stimuli that will be brought to their receptive fields by an impending eye movement. This neural mechanism, known as predictive remapping, has been suggested to underlie spatial constancy. Inhibition of return (IOR) is a bias against recently attended locations. The present study examined whether predictive remapping is a mechanism underlying IOR effects observed in environmental coordinates. The participant made saccades to a peripheral location after an IOR effect had been elicited by an onset cue and discriminated a target presented around the time of saccade onset. Immediately before the required saccade, IOR emerged at the retinal locus that would be brought to the cued location. A second task in which the participant maintained fixation during the entire trial ruled out the possibility that this IOR effect was simply the spillover of IOR from the cued location. These findings, for the first time, provide direct behavioral evidence that predictive remapping is a mechanism underlying environmental IOR.     

Top-down influences make saccades deviate away: the case of endogenous cues

We tested a recent hypothesis suggesting that the eye deviates away from a location when top-down preparation can influence target selection. Participants had to make an eye movement to a peripheral target. Before the upcoming target, a central cue indicated the likely target location. Results show that when the target was presented at a location different from that indicated by the cue, eye movements to the target deviated away from the cued location. Because central cues are under top-down control, the present results are in line with a determining role of top-down preparation on saccade direction. These results contrast with the findings reported in a similar paradigm executed with hand movements, in which the movements were mostly initiated in the direction of the cued location. Therefore, we conclude that inhibitory effects typically observed when executing eye movements may not be observed when executing hand movements in similar conditions.     

Spatial orienting of attention in stereo depth

The aim of this study was to investigate the spatial orienting of visual attention in depth under purely stereoscopic viewing conditions. Random-dot stereograms were used to present disparity-defined target stimuli that were either validly or invalidly cued in depth. In separate tasks, participants responded either to the relative depth of the target (protruding vs. receding) or to its shape (square vs. diamond). Stimulus onset asynchronies (SOAs) between an uninformative exogenous cue and target were varied from 250 to 600?ms. For both tasks, mean response times (RTs) were shorter for validly than invalidly cued target depths and this RT advantage was essentially restricted to the shortest SOA of 250?ms. These results indicate that attention can be reflexively allocated to locations in stereo depth under conditions of low perceptual load, and independent of whether depth is relevant to the task or not.     

The relationship between covert and overt attention in endogenous cuing

In a standard Posner paradigm, participants were endogenously cued to attend to a peripheral location in visual space without making eye movements. They responded faster to target letters presented at cued than at uncued locations. On some trials, instead of a manual response, they had to move their eyes to a location in space. Results showed that the eyes deviated away from the validly cued location; when the cue was invalid and attention had to be allocated to the uncued location, eye movements also deviated away, but now from the uncued location. The extent to which the eyes deviated from cued and uncued locations was related to the dynamics of attention allocation. We hypothesized that this deviation was due to the successful inhibition of the attended location. The results imply that the oculomotor system is not only involved during the endogenous direction of covert attention to a cued location, but also when covert attention is directed to an uncued location. It appears that the oculomotor system is activated wherever spatial attention is allocated. The strength of saccade deviation might turn out to be an important measure for the amount of attention allocated to any particular location over time.     

Automatic attentional orienting to other people’s gaze in schizophrenia

Explicit tests of social cognition have revealed pervasive deficits in schizophrenia. Less is known of automatic social cognition in schizophrenia. We used a spatial orienting task to investigate automatic shifts of attention cued by another person’s eye gaze in 29 patients and 28 controls. Central photographic images of a face with eyes shifted left or right, or looking straight ahead, preceded targets that appeared left or right of the cue. To examine automatic effects, cue direction was non-predictive of target location. Cue–target intervals were 100, 300, and 800?ms. In non-social control trials, arrows replaced eye-gaze cues. Both groups showed automatic attentional orienting indexed by faster reaction times (RTs) when arrows were congruent with target location across all cue–target intervals. Similar congruency effects were seen for eye-shift cues at 300 and 800?ms intervals, but patients showed significantly larger congruency effects at 800?ms, which were driven by delayed responses to incongruent target locations. At short 100-ms cue–target intervals, neither group showed faster RTs for congruent than for incongruent eye-shift cues, but patients were significantly slower to detect targets after direct-gaze cues. These findings conflict with previous studies using schematic line drawings of eye-shifts that have found automatic attentional orienting to be reduced in schizophrenia. Instead, our data indicate that patients display abnormalities in responding to gaze direction at various stages of gaze processing—reflected by a stronger preferential capture of attention by another person’s direct eye contact at initial stages of gaze processing and difficulties disengaging from a gazed-at location once shared attention is established.     

Inhibitory interaction: the effects of multiple non-predictive visual cues

When the interval between a non-predictive cue and a target appearing at the same spatial location is longer than about 200 ms, target performance is typically poorer than when the cue and target appear at different locations. Recent studies have shown that this effect, known as inhibition of return (IOR), can occur at multiple cued locations, and is enhanced when multiple cues are presented at the same spatial location. However, little is known about how the magnitude of IOR at one spatial location is influenced by a subsequent or preceding cue presented at a different spatial location. We investigated this issue by presenting single or multiple cues at varying inter-cue intervals prior to target onset. Results suggest that the magnitude of IOR at a given location is influenced by the presentation of a preceding cue, but that once IOR occurs, it is unaffected by the presentation of a subsequent cue.     

Presaccadic attention allocation and express saccades

Express saccades are visually-guided saccades that are characterized by an extremely short latency of about 100 ms. The present experiments tested the hypothesis that a disengagement of visual attention is necessary for the generation of express saccades. All subjects produced large numbers of express saccades in the gap paradigm, in which the fixation stimulus is removed 200 ms before target onset (Exp. 1), but not in the overlap paradigm, in which the fixation stimulus remains on during the entire trial (Exp. 2). By means of peripheral cues (Exps. 3–5) and central cues (Exps. 6–7), visual attention was directed at the target location for the saccade before the actual appearance of the saccade target. In all experiments, the location cues facilitated rather than abolished express saccades. The generation of express saccades was facilitated even when the currently fixated visual stimulus was not removed before target onset (fixation-overlap; Exps. 5–7). The results are explained by the hypothesis that a disengagement of a separate fixation system is necessary for the generation of express saccades, a hypothesis that is in line with current neurobiological findings.     

Importance of precue location in directing attention

In location-precuing experiments, accuracy in discrimination of T-like characters improves with increasing time between the precue and the target. In this experiment, two central and two peripheral cue locations were examined using 13 different cue-target intervals from 0 to 234 msec. Accuracy was the same when trials were cued from the two peripheral locations (two thirds distance between fixation and target or distal to the target location). Centrally cued trials (cues at fixation or next to fixation) resulted in slower onset of attentional effects than peripherally cued trials, but there was greater accuracy at long cue-target intervals for central than for peripheral cues. Data are compared to previously published research.     

不同SOA下视觉返回抑制对视听觉整合的调节作用

基于外源性线索-靶子范式, 采用2(线索-靶子间隔时间, stimulus onset asynchronies, SOA：400~600 ms、1000~1200 ms) × 3(目标刺激类型：视觉、听觉、视听觉) × 2(线索有效性：有效线索、无效线索)的被试内实验设计, 要求被试对目标刺激完成检测任务, 以考察视觉线索诱发的返回抑制(inhibition of return, IOR)对视听觉整合的调节作用, 从而为感知觉敏感度、空间不确定性及感觉通道间信号强度差异假说提供实验证据。结果发现：(1) 随SOA增长, 视觉IOR效应显著降低, 视听觉整合效应显著增强; (2) 短SOA (400~600 ms)时, 有效线索位置上的视听觉整合效应显著小于无效线索位置, 但长SOA (1000~1200 ms)时, 有效与无效线索位置上的视听觉整合效应并无显著差异。结果表明, 在不同SOA条件下, 视觉IOR对视听觉整合的调节作用产生变化, 当前结果支持感觉通道间信号强度差异假说。     

The control of saccade trajectories: direction of curvature depends on prior knowledge of target location and saccade latency

Recent reports have shown that saccades can deviate either toward or away from distractors. However, the specific conditions responsible for the change in initial saccade direction are not known. One possibility, examined here, is that the direction of curvature (toward or away from distractors) reflects preparatory tuning of the oculomotor system when the location of the target and distractor are known in advance. This was investigated by examining saccade trajectories under predictable and unpredictable target conditions. In Experiment 1, the targets and the distractors appeared unpredictably, whereas in Experiment 2 an arrow cue presented at fixation indicated the location of the forthcoming target prior to stimulus onset. Saccades were made to targets on the horizontal, vertical, and principal oblique axis, and distractors appeared simultaneously at an adjacent location (a separation of +/- 45 degrees of visual angle). On average, saccade trajectories curved toward distractors when target locations were unpredictable and curved away from distractors when target locations were known in advance. There was no overall difference in mean saccade latencies between the two experiments. The magnitude of the distractor modulation of saccade trajectory (either toward or away from) was comparable across the different saccade directions (horizontal, vertical, and oblique). These results are interpreted in terms of the time course of competitive interactions operating in the neural structures involved in the suppression of distractors and the selection of a saccade target. A relatively slow mechanism that inhibits movements to distractors produces curvature away from the distractor. This mechanism has more time to operate when target location is predictable, increasing the likelihood that the saccade trajectory will deviate away from the distractor.     

Inhibition of return generated by voluntary saccades is independent of attentional momentum

Summoning attention to a peripheral location, either by a peripheral cue with the eyes fixed or when a voluntary saccade is made to it and gaze is then returned to the centre, delays detection of subsequent targets at that location compared to a location in the opposite visual field. It has been proposed that oculomotor activation generates this inhibition of return (IOR). This account presupposes that the asymmetry in detection results from inhibition at the cued location rather than facilitation at the uncued location. This has been confirmed for exogenously generated IOR. However, it has not, heretofore, been confirmed for “IOR” generated by voluntary saccades. The current study investigated whether the asymmetry in target detection, elicited either by a peripheral flash or by an eye movement generated in response to a central arrowhead, reflects facilitation at the opposite location due to the path of attentional momentum. Reaction times at the cued location were slower than reaction times at the opposite or perpendicular locations, which did not differ. Opposite facilitation due to attentional momentum requires that opposite be faster than perpendicular, which was not obtained. The results were the same whether IOR was generated by an exogenous cue or by a saccade executed endogenously to a central arrow.     

On the uniqueness of attentional capture by uninformative gaze cues: facilitation interacts with the Simon effect and is rarely followed by IOR.

Orienting to an uninformative peripheral cue is characterized by a brief facilitation followed by a long-lasting inhibition once attention is removed from the cued location. Although central gaze cues cause reflexive orienting, the inhibitory effect that is relatively ubiquitous following exogenous orienting to uninformative peripheral cues has been relatively rare. We hypothesized that IOR might be seen following gaze-induced orienting if attention were effectively returned to centre by a return gaze or return flash. The timecourse of gaze-directed orienting was measured by varying the interval between the gaze cue and a peripheral target requiring an orientation discrimination (permitting measurement of the Simon effect). Significant facilitation was observed at all but the longest SOA tested, 2,880 ms, by which time the facilitation had disappeared with no evidence of IOR. Gaze-induced cuing (which was unaffected by return cue condition) interacted with the Simon effect, decreasing it at the gazed-at location, a pattern that is not seen with more typical endogenous and exogenous cuing.     

Inhibitory tagging at subsequently fixated locations: Generation of “inhibition of return” without saccade inhibition

In two experiments, an inhibitory tag was activated by a peripheral cue after which a saccade was made to either the cued or, with equal probability, the uncued location. Key press RTs were measured for detecting a target that then appeared, with equal probability, either at fixation or at an eccentric location. In Experiment 1, the peripheral cue onset 400 ms before the saccade instruction, and participants therefore were obliged to inhibit a saccade towards the cue. Detection was slower at the cued location whether it appeared at, or eccentric from, fixation. In Experiment 2, the peripheral cue onset after the instruction to make the saccade but before the eyes had moved. Inhibitory tagging was again observed for targets at fixation, but the effect was smaller than for eccentric targets. These findings confirm that withdrawal of attention from a cued location is not required to generate an inhibitory tag, and that the cued locus remains inhibited even if it is subsequently attended and a saccade made to fixate it. Moreover, saccade inhibition is not sufficient to account for inhibitory tagging, although it may also engender an independent inhibitory effect.     

Investigating the parameters of transsaccadic memory: inhibition of return impedes information acquisition near a saccade target

A limited amount of visual information is retained between saccades, which is subsequently stored into a memory system, such as transsaccadic memory. Since the capacity of transsaccadic memory is limited, selection of information is crucial. Selection of relevant information is modulated by attentional processes such as the presaccadic shift of attention. This involuntary shift of attention occurs prior to execution of the saccade and leads to information acquisition at an intended saccade target. The aim of the present study was to investigate the influence that another attentional effect, inhibition of return (IOR), has on the information that gets stored into transsaccadic memory. IOR is the phenomenon where participants are slower to respond to a cue at a previously attended location. To this end, we used a transsaccadic memory paradigm in which stimuli, oriented on a horizontal axis relative to saccade direction, are only visible to the participant before executing a saccade. Previous research showed that items in close proximity to a saccade target are likely to be reported more accurately. In our current study, participants were cued to fixate one of the stimulus locations and subsequently refixated the centre fixation point before executing the transsaccadic memory task. Results indicate that information at a location near a saccade landing point is less likely to be acquired into transsaccadic memory when this location was previously associated with IOR. Furthermore, we found evidence which implicates a reduction of the overall amount of elements retained in transsaccadic memory when a location near a saccade target is associated with IOR. These results suggest that the presaccadic shift of attention may be modulated by IOR and thereby reduces information acquisition by transsaccadic memory.     

Bottom-up effects modulate saccadic latencies in well-known eye movement paradigm

A well-known eye movement paradigm combines saccades (fast eye movements) with a perceptual discrimination task. At a variable time after the onset of a central arrow cue indicating the target direction [the stimulus onset asynchrony (SOA)], discrimination symbols appear briefly at saccade target and non-target locations. A previous study revealed an unexpected effect of SOA on saccadic latencies: latencies were longer in trials with longer SOAs. It was suggested that this effect reflects a top-down process as observers may wait for the discrimination symbol to appear before executing saccades. However, symbol onsets may also modulate saccade latencies from the bottom-up. To clarify the origin of the SOA effect on latencies in this paradigm, we used a simplified version of the original task plus two new symbol onset conditions for comparison. The results indicate that the modulation of saccadic latencies was not due to a top-down strategy, but to a combination of two opposing bottom-up effects: the symbol onsets at the target location shortened saccade latencies, while symbol onsets at non-target locations lengthened saccade latencies.     

Inhibition of return with rapid serial shifts of attention: implications for memory and visual search

Horowitz and Wolfe (2001) suggested that inhibition of return (IOR) should not be observed in tasks that involve rapid deployments of attention. To examine this issue, five of six possible locations were sequentially cued with either short-duration peripheral cues (50 msec) or long-duration peripheral cues (500 msec). As was expected, IOR was observed in the first two experiments at every cued location with the long-duration cues, with the magnitude of IOR decreasing for earlier cued locations relative to later cued locations. In the short-cue condition, IOR was observed at only one cued location (the second to last). The pattern of results for the short-duration cues was found regardless of whether the fixation cue was of a short (Experiment 1) or a long (Experiment 2) duration. In Experiment 3, the final fixation cue was removed, and IOR was again observed at virtually all locations in both the short- and the long-cue conditions. These findings indicate that IOR can be observed at multiple locations when attention is shifted rapidly between locations.     

Vector averaging of inhibition of return

Observers detected targets presented 400 msec after a display containing one cue or two to four cues displayed simultaneously in randomly selected locations on a virtual circle around fixation. The cue arrangement was completely uninformative about the upcoming target’s location, and eye position was monitored to ensure that the participants maintained fixation between the cue and their manual detection response. Reflecting inhibition of return (IOR), there was a gradient of performance following single cues, with reaction time decreasing monotonically as the target’s angular distance from the cued direction increased. An equivalent gradient of IOR was found following multiple cues whose center of gravity fell outside the parafoveal region and, thus, whose net vector would activate an orienting response. Moreover, on these trials, whether or not the targeted location had been stimulated by a cue had little effect on this gradient. Finally, when the array of cues was balanced so that its center of gravity was at fixation, there was no IOR. These findings, which suggest that IOR is an aftermath of orienting elicited by the cue, are compatible with population coding of the entire cue (as a grouped array for multiple cues) as the generator of IOR.     

Surprising depth cue captures attention in visual search

A substantial amount of evidence indicates that surprising events capture attention. The present study was primarily intended to investigate whether expectancy discrepant depth information also is able to capture attention immediately and—more specifically—whether cues that are relatively closer or farther differentially modulate behavior. For this purpose, participants had to identify one of two target letters in a search display. Stimulus positions were initially cued by uninformative placeholders. After half of the trials, the cue at the target position was suddenly and unexpectedly (critical trial) displayed closer to or farther from the observer. In line with previous research, both depth cues captured attention on their very first appearance. Performance in the critical trial was superior to the error rates in the trials without depth cue and was even above the performance in subsequent trials that included depth cue. This effect was only observed when the cue preceded the target by 400 ms. Using a shorter cue-stimulus interval of 100 ms, only a delayed improvement was observed, which denotes a typical feature of surprise capture. Moreover, response times were faster in trials comprising a depth cue, and this was already true for the critical trial. Apart from that, no other marked differences between near and far depth cues were observed. Therefore, the present results emphasize that surprising depth information indeed captures attention. However, in contrast to other perceptual tasks, search performance was not considerably influenced by relative position in depth.