The manifestation of attentional capture: facilitation or IOR depending on task demands

Fixation offset decreases manual inhibition of return (IOR) in detection and discrimination tasks

Attention can be covertly shifted to peripheral stimuli to improve their processing. However, attention is also then inhibited against returning to the previously attended location; thus, both detection and discrimination of a stimulus presented at that location decrease (the inhibition of return [IOR] effect). The after-effect of the covert orienting hypothesis postulates a close link between attention shifting, IOR, and oculomotor control. The fixation offset, which improves the generation of saccades, decreases IOR in detection tasks, suggesting a close link between IOR and oculomotor control. However, according to some alternative views (e.g., the input-based IOR hypothesis and the object files segregation/integration hypothesis), IOR may be related to some sensory rather than motor processes. Some studies support that view and show that IOR may occur differently in detection and discrimination tasks and that oculomotor processes do not affect IOR in tasks where manual responses are required and eye movements are suppressed. Two experiments presented in this article show that removing the fixation point decreases manual IOR in detection and discrimination tasks. The results are discussed in terms of various theoretical approaches.

Detection cost: A nonnegligible factor contributing to inhibition of return in the discrimination task under the cue-target paradigm

The three-factor model argues that the spatial orienting benefit triggered by the cue, the spatial selection benefit of cue-target matching, and the detection cost of distinguishing the cue from the target contribute to the measured inhibition of return (IOR) effect. According to the three-factor model, the spatial selection benefit dominates the occurrence of the IOR effect in the discrimination task, while the detection cost is negligible. The present study verified the three-factor model in the discrimination task under the cue-target paradigm by manipulating the spatial location and nonspatial feature consistency of the cue and the target as well as the promotion or hindrance of attentional disengagement from the cued location with a central reorienting cue. The results indicated that the three factors of the three-factor model contributed to the measured IOR effect in the discrimination task. Interestingly, the IOR effect was stable when the cue and target were perfectly repeated and attention was maintained at the cued location, implying that detection cost was not a negligible factor. The current study supported the contribution of all three factors in the three-factor model to the measured IOR effect; however, we argue that the role of detection cost in the discrimination task under different paradigms should be further refined.

Does the construction retrieval account apply to cross‐modal inhibition of return in semantic context?

The traditional attentional reorienting hypothesis is insufficient to explain spatial and nonspatial inhibition of return (IOR). Therefore, a construction retrieval account that includes the influence of top-down attentional sets has been proposed and can explain both spatial and nonspatial IOR. However, it remains unknown whether the construction retrieval account can be applied to non-surface features of stimuli, as well as whether its construction and retrieval mechanisms are supra-modal. The present study manipulated semantic feature congruency and spatial location congruency between the prime and the target in cross-modal audio-visual and visual-audio experimental conditions, respectively, by orthogonally combining spatial and nonspatial IOR paradigms. Our results showed that there was an interaction between semantic feature congruency and spatial location congruency controlled by the attentional sets, and that this interaction was consistent in cross-modal audio-visual and visual-audio conditions. These results suggest that the construction retrieval account can be applied to abstract semantic features and that its construction and retrieval mechanisms are supra-modal. The present study extends the application scope of the construction retrieval account and promotes the interpretation of IOR under a unified theoretical framework.

Location-response binding and inhibition of return in a detection task

In the present study, we investigated the binding of location and response in a detection task of the target-target paradigm of inhibition of return (IOR). Results showed a cost of responding to a target at the repeated location (IOR) when the response was not repeated and an effect of facilitation of return (FOR) when the response was repeated. These findings suggest that when responding to a target, its location and the response to it are integrated together. In addition, an analysis of the Vincentized cumulative response time (RT) distribution further showed that memory retrieval of event representations requires time to operate. These findings were discussed according to the theoretical framework of event files.

Contextual Similarity Between Successive Targets Modulates Inhibition of Return in the Target-Target Paradigm

Inhibition of return (IOR) refers to slower responses to a target presented at a previously cued vs. uncued location. The present study investigated the role of memory retrieval in IOR by manipulating the contextual similarity between two successive targets in the target-target IOR paradigm. Successive targets were presented in either the same color (same-context condition) or different colors (different-context condition). Results of two experiments showed that IOR was greater in the same-context than the different-context condition. In addition, Experiment 2 showed that this context effect occurs with long response times (RTs), suggesting that memory retrieval, which requires time to manifest, plays an important role in IOR.

When do response-related episodic retrieval effects co-occur with inhibition of return?

At some point, spatial priming effects more faithfully reflect response selection processes than they do attentional orienting or sensory processes. Findings from the spatial cueing literature suggest that two factors may be critical: (1) the amount of identity processing that is required in order to respond correctly (feature-based response hypothesis), and (2) the amount of spatial processing that is required in order to respond correctly (space-based response hypothesis). To test the first hypothesis, we manipulated whether observers made single keypress detection or two-choice localization responses to serially presented stimuli in peripheral vision and whether stimulus identity information processing was necessary before responding. Responses were always slowest when the target location repeated, consistent with an attentional orienting bias independent of keypress responding (i.e., inhibition of return; IOR). The localization procedure revealed a subtle additional cost for changing the target location and repeating a response, consistent with a response-related episodic retrieval effect predicted by the Theory of Event Coding (TEC). Neither effect was modulated by the need to discriminate features. To test the second hypothesis, we made spatial processing indispensable to response selection by requiring a decision between a detection and localization response, depending on where the target appeared. IOR was eliminated for detection, but not localization, responses, consistent with the TEC. Collectively, the findings suggest that the amount of space-based, but not feature-based, processing that is required to determine a response is responsible for the response retrieval effects that can co-occur with IOR.

On the time course of spatial cueing: Dissociating between a set for fast reorienting and a set for cue-target segregation

The present study tests whether two different manipulations leading to an earlier appearance of Inhibition of Return might operate by setting the system in different ways. Whereas the use of a range of very long SOAs has been proposed to set the system for an early reorienting of attention (Cheal & Chastain, 2002), introducing a distractor at the location opposite the target seems to induce a set to represent the cue and the target as separated events instead of the same event (Lupiáñez et al., 1999, 2001). The effects of these two manipulations were directly compared by using a spatial stroop paradigm. Although both manipulations altered the time course of cueing effects, we report here a pattern of critical dissociations: (i) the distractor manipulation was unique in introducing a shift towards more negative cueing affecting generally all levels of SOA, including the shortest 100 ms SOA; and (ii) the distractor manipulation, but not the range of SOAs, was also able to prevent the expected interaction between spatial stroop effects and cueing effects at the shortest SOA, typically found in previous experiments in the absence of a distractor (Funes et al., 2003). This pattern of dissociations is well accommodated into the hypothesis that these two attentional sets are different in nature.

Electrophysiological Correlates of the Effect of Task Difficulty on Inhibition of Return

Inhibition of return (IOR) refers to slower responses to targets that occur at a previously attended location than to those at control locations. Previous studies on the impact of task difficulty on IOR have shown conflicting results. However, these studies failed to match low-level characteristics of stimuli (e.g., size, color, and luminance) across difficulty levels, and so might have confounded the effect of task difficulty with that of stimulus characteristics. Hence, whether and how task difficulty modulates IOR remain largely unknown. This study utilized the event-related potentials (ERPs) technique in combination with a cue-target paradigm to tackle this question. Task difficulty was manipulated by changing the position of a gap in a rectangle stimulus, while stimulus size, color, and luminance were precisely matched. IOR was observed in reaction times across all difficulty levels but was found in accuracy at the medium level only. The modulation effect of task difficulty on IOR was also evident in the N1 and P2 ERP components, which showed significantly weaker IOR effects at the medium difficulty level than at the easy and hard levels. It is suggested that the modulation of IOR by task difficulty involves both perceptual and post-perceptual processes.

The Time Course of Inhibition of Return: Evidence from Steady-State Visual Evoked Potentials

Inhibition of return (IOR) refers to slower responses to targets at a previously cued location than that at an uncued location. The time course of IOR has long been a topic of interest in the field. Investigations into the time course of IOR are typically performed by examining the magnitude of IOR under various cue-target onset asynchrony (CTOA) conditions. Therefore, the results are vulnerable to influence of factors that could affect the target processes (e.g., the frequency of the target type). In the present study, steady-state visual evoked potentials (SSVEPs) were implemented to directly take a continuous measurement of the degree to which cued location is processed, eliminating the influence mentioned above. The results indicate that, relative to the baseline interval (−400 to 0 ms), the presence of peripheral cues generated a typical two-stage effect on the SSVEP amplitude evoked by a 20 Hz flicker. Specifically, after the onset of the peripheral cues, the SSVEP amplitude first showed a significant increase, which subsequently turned into a significant inhibition effect after 200 ms. These results provide a continuous time course diagram of the cueing effect and suggest an effective way for future investigations of controlling the masking effects of target stimuli processing on IOR.

Does Target Object Processing Affect Reaction Times in Simple Detection Spatial Cueing Tasks?

The current study tested the effect of varying target type and target set size during simple detection versions of Posner's exogenous spatial cueing task. The four target conditions consisted of a single letter, a single number, one of four possible letters, or one of four possible numbers. Responses were faster for numbers than for letters, but only when the cue-target lag was short, the target set included more than one potential number, and the cue and target appeared in different locations. These findings suggest that even during detection tasks, responses are influenced by the object features of the target. Methodological implications for spatial cueing studies and other types of visual perception research were discussed.

The Influence of Acute Intense Exercise on Exogenous Spatial Attention Depends on Physical Fitness Level

We investigated the effect of a previous bout of intense exercise on exogenous spatial attention. In Experiment 1, a group of participants performed an exogenous spatial task at rest (without prior effort), immediately after intense exercise, and after recovering from an intense exercise. The analyses revealed that the typical “facilitation effect” (i.e., faster reaction times on cued than on uncued trials) immediately after exercise was positively correlated with participants’ fitness level. In Experiment 2, a high-fit and a low-fit group performed the same task at rest (without prior effort) and immediately after an intense exercise. Results revealed that, after the bout of exercise, only low-fit participants showed reduced attentional effects compared to the rest condition. We argue that the normal functioning of exogenous attention was influenced by intense effort, affecting low-fit participants to a larger extent than to high-fit participants. As a consequence, target processing was prioritized over irrelevant stimuli.

What causes IOR? Attention or perception? - manipulating cue and target luminance in either blocked or mixed condition

Inhibition of return (IOR) refers to the performance disadvantage when detecting a target presented at a previously cued location. The current paper contributes to the long-standing debate whether IOR is caused by attentional processing or perceptual processing. We present a series of four experiments which varied the cue luminance in mixed and blocked conditions. We hypothesised that if inhibition was initialized by an attentional process the size of IOR should not vary in the blocked condition as participants should be able to adapt to the level of cue luminance. However, if a perceptual process triggers inhibition both experimental manipulations should lead to varying levels of IOR. Indeed, we found evidence for the latter hypothesis. In addition, we also varied the target luminance in blocked and mixed condition. Both manipulations, cue luminance and target luminance, affected IOR in an additive fashion suggesting that the two stimuli affect human behaviour on different processing stages.

Nonspecific competition underlies transient attention

Cueing a target by abrupt visual stimuli enhances its perception in a rapid but short-lived fashion, an effect known as transient attention. Our recent study showed that when targets are cued at a constant, central location, the emergence of the transient performance pattern was dependent on the presence of competing distractors, whereas targets presented in isolation were enhanced in a sustained manner (Wilschut et al., PLoS ONE, 6:e27661, 2011). The current study examined in more detail whether the transience depends on the specific nature of the competition. We first replicated and extended the competition-dependent transient pattern for peripheral and variable target locations. We then investigated the role of feature similarity, compatibility, and proximity. Both competition by feature similarity and compatibility between the target and distractors were found to impair performance, but effects were additive with the effects of the cueing interval and did not change the transient performance function. Varying the spatial distance between target and distractors yielded mixed evidence, but here too a transient pattern could be observed for targets flanked by both close and far distractors. The results thus show that the presence or absence of competition determines whether attention appears transient or sustained, while the specific nature of the competition (in terms of location or feature) affects selection independent of time.

Spatial distribution of attentional bias in visuo-spatial working memory following multiple cues

When attention is focused on one location, its spatial distribution depends on many factors, such as the distance between the attended location and the target location, the presence of visual meridians in between them, and the way, endogenous or exogenous, by which attention is oriented. However, it is not well known how attention distributes when more than one location is endogenously or exogenously cued, which was the focus of the current study. Furthermore, the distribution of attention has been manly investigated in perception. In the present study we faced this issue from a different perspective, by examining the spatial distribution of the attentional bias in visuo-spatial working memory (VSWM), when attention is oriented either exogenously or endogenously, i.e., after two peripheral vs. central symbolic cues (also manipulating cue-target predictability). Results indicated a systematic difference between endogenous and exogenous attention regarding the distribution of the attentional bias over VSWM. In fact, attentional bias following endogenous cues was affected by the presence of visual meridians and by the split of the attentional focus, converging in a unipolar attentional distribution, independently of cue-target predictability. On the other hand, when pulled by exogenous cues, attention distributed uni-modally or multi-modally depending on the distance between the cued locations, with larger effects for highly predictive cues. Results are discussed in terms of space-based, object-based and perceptual grouping mechanisms.

Multiple cueing dissociates location- and feature-based repetition effects

There is an extensive literature on the phenomenon of inhibition of return (IOR): When attention is drawn to a peripheral location and then removed, response time is delayed if a target appears in the previously inspected location. Recent research suggests that non-spatial attribute repetition (i.e., if a target shares a feature like color with the earlier, cueing, stimulus) can have a similar inhibitory effect, at least when the target appears in the previously cued location. What remains unknown is whether location- and feature-based inhibitory effects can be dissociated. In the present study, we used a multiple cueing approach to investigate the properties of location- and feature-based repetition effects. In two experiments (detection, and discrimination), location-based IOR was absent but feature-based inhibition was consistently observed. Thus, the present results indicate that feature- and location-based inhibitory effects are dissociable. The results also provide support for the view that the attentional consequences of multiple cues reflect the overall center of gravity of the cues. We suggest that the repetition costs associated with feature and location repetition may be best understood as a consequence of the pattern of activation for object files associated with the stimuli present in the displays.

Beyond the inhibition of return of attention: reduced habituation to threatening faces in schizophrenia

Attention deficits are prominent among the core symptoms of schizophrenia. A recent meta-analysis has suggested that patients with schizophrenia have a deficit in endogenous disengagement of attention. In this research, we used a standard spatial cueing paradigm to examine whether the attention deficit of such patients is due to impaired attentional disengagement or defective novelty detection/habituation processes. In a spatial cueing procedure with peripheral non-predictive cues and a detection task, we manipulated the valence of either the cue or the target (i.e., a threatening vs. scrambled face) in two separate experiments. The control group exhibited a smaller inhibition of return (IOR) effect only when the target had an emotional load, not when the cue had an emotional load. In the patient group, a larger emotional effect appeared when the threatening face was the target; by contrast, no effect of valence was observed when the threatening face was the cue: IOR was delayed or completely absent independently of valence. The present findings are in conflict with the hypothesis that IOR is due to the disengagement of attention and the subsequent inhibition to return. Instead, they seem to suggest a cost in detecting new information at a previously cued location. From this perspective, it seems that patients with schizophrenia might have a deficit in detecting new information and considering it as new in the current context.

Visual unimodal grouping mediates auditory attentional bias in visuo-spatial working memory

Audiovisual links in spatial attention have been reported in many previous studies. However, the effectiveness of auditory spatial cues in biasing the information encoding into visuo-spatial working memory (VSWM) is still relatively unknown. In this study, we addressed this issue by combining a cuing paradigm with a change detection task in VSWM. Moreover, we manipulated the perceptual organization of the to-be-remembered visual stimuli. We hypothesized that the auditory effect on VSWM would depend on the perceptual association between the auditory cue and the visual probe. Results showed, for the first time, a significant auditory attentional bias in VSWM. However, the effect was observed only when the to-be-remembered visual stimuli were organized in two distinctive visual objects. We propose that these results shed new light on audio-visual crossmodal links in spatial attention suggesting that, apart from the spatio-temporal contingency, the likelihood of perceptual association between the auditory cue and the visual target can have a large impact on crossmodal attentional biases.

Early perceptual interactions shape the time course of cueing

Performance in spatial cueing tasks is characterized by a rapid attentional enhancement with increasing cue-target SOA. We recently found that this enhancement function also applies when the cue and the target are presented invariably at a single central location, suggesting a universal cueing time course [Wilschut et al., 2011, PLoS ONE, 6, e27661]. However, using a very similar cueing task, Nieuwenstein et al. [2009, JoV, 9, 1-14] have found a rather different pattern, namely a U-shaped deficit in performance after a cue-like stimulus. The present study varied the properties of the cue and the target in order to investigate the mechanisms underlying the different time functions. In four experiments, cueing was found to either improve or decrease performance with increasing SOA, depending on the type of target that was used. In addition, the level of performance at the shortest cue-target intervals (33-83ms) was dependent on the relative strength of the cue and the target, akin to what has been found in visual masking studies. The results suggest that cueing shapes performance via two mechanisms, one sensory-related and one attention-related, the combination of which results in either U-shaped or monotonic patterns.

Is “Inhibition of Return” due to the inhibition of the return of attention?

Inhibition of Return (IOR) is usually explained in terms of orienting–reorienting of attention, emphasizing an underlying mechanism that inhibits the return of attention to previously selected locations. Recent data challenge this explanation to the extent that the IOR effect is observed at the location where attention is oriented to, where no reorienting of attention is needed. To date, these studies have involved endogenous attentional selection of attention and thus indicate a dissociation between the voluntary attention of spatial attention and the IOR effect. The present work demonstrates a dissociation between the involuntary orienting of spatial attention and the IOR effect. We combined nonpredictive peripheral cues with nonpredictive central orienting cues (either arrows or gaze). The IOR effect was observed to operate independent of involuntary spatial orienting. These data speak against the “ reorienting hypothesis” of IOR. We suggest an alternative explanation whereby the IOR effect reflects a cost in detecting a new event (the target) at the location where another event (a cue) was coded before.

Two cognitive and neural systems for endogenous and exogenous spatial attention

Orienting of spatial attention is a family of phylogenetically old mechanisms developed to select information for further processing. Information can be selected via top-down or endogenous mechanisms, depending on the goals of the observers or on the task at hand. Moreover, salient and potentially dangerous events also attract spatial attention via bottom-up or exogenous mechanisms, allowing a rapid and efficient reaction to unexpected but important events. Fronto-parietal brain networks have been demonstrated to play an important role in supporting spatial attentional orienting, although there is no consensus on whether there is a single attentional system supporting both endogenous and exogenous attention, or two anatomical and functionally different attentional systems. In the present paper we review behavioral evidence emphasizing the differential characteristics of both systems, as well as their possible interactions for the control of the final orienting response. Behavioral studies reporting qualitative differences between the effects of both systems as well as double dissociations of the effects of endogenous and exogenous attention on information processing, suggest that they constitute two independent attentional systems, rather than a single one. Recent models of attentional orienting in humans have put forward the hypothesis of a dorsal fronto-parietal network for orienting spatial attention, and a more ventral fronto-parietal network for detecting unexpected but behaviorally relevant events. Non-invasive neurostimulation techniques, as well as neuropsychological data, suggest that endogenous and exogenous attention are implemented in overlapping, although partially segregated, brain circuits. Although more research is needed in order to refine our anatomical and functional knowledge of the brain circuits underlying spatial attention, we conclude that endogenous and exogenous spatial orienting constitute two independent attentional systems, with different behavioral effects, and partially distinct neural substrates.

Facilitation versus inhibition in non-spatial attribute discrimination tasks

Inhibition of Return is a delay in initiating attentional shifts to previously inspected locations. It has been explained as a mechanism to facilitate visual search of a scene by inhibiting the allocation of attention to locations that have already been examined. We (Hu, Samuel, & Chan, Journal of Experimental Psychology: General, 2010) recently demonstrated that similar processing costs can appear when a non-spatial attribute (color or shape) repeats-detection of a target stimulus was slower if the target shared color or shape with a recently presented cue. In the current study, we test whether such inhibitory effects occur for non-spatial attribute repetition when observers must make a discrimination judgment about targets. We found two independent effects: First, there was a standard location-based IOR effect-target discrimination was slower when the target appeared in the same location as a preceding cue. Second, reaction times were faster if the target's color or shape matched the cue's color or shape; this facilitation effect contrasts with both the location-based inhibition that was present in the current experiments, and with the inhibitory effect of feature repetition in our previous detection task study. The data are best accounted for by a three-factor model recently suggested by Lupiáñez (Attention and time, 2010).

Neural correlates of spatial orienting in the human superior colliculus

A natural visual scene contains more information than the visual system has the capacity to simultaneously process, requiring specific items to be selected for detailed analysis at the expense of others. Such selection and inhibition are fundamental in guiding search behavior, but the neural basis of these mechanisms remains unclear. Abruptly appearing visual items can automatically capture attention, but once attention has been directed away from the salient event, return to that same location is slowed. In non-human primates, signals associated with attentional capture (AC) and subsequent inhibition of return (IOR) have been recorded from the superior colliculus (SC)--a structure known to play a pivotal role in reflexive spatial orienting. Here, we sought to establish whether similar signals could be recorded from the human SC, as well as early retinotopic cortical visual areas, where signals associated with AC and IOR have yet to be investigated with respect to oculomotor responses. Using an optimized oculomotor paradigm together with high-field, high-spatial resolution functional magnetic resonance imaging and high-speed eye tracking, we demonstrate that BOLD signal changes recorded from the human SC correlate strongly with our saccadic measures of AC and IOR. A qualitatively similar pattern of responses was found for V1, but only the inhibitory response associated with IOR persisted through V2 and V3. Although the SC plays a role in mediating these automatic attentional biasing signals, the source of these signals is likely to lie in higher cortical areas.

An attentional approach to study mental representations of different parts of the hand

The aim of this study is to investigate whether the fingers are represented separately from the palm. An exogenous spatial orientation paradigm was used where participants had to detect a tactile stimulus that could appear on the palm, the middle finger or the ring finger of the left hand. The tactile target was preceded by a non-predictive cue using different stimulus-onset asynchronies (SOA). We observed a Facilitation Effect in the palm and inhibition of return (IOR) for fingers using a short cue-target SOA, whereas the IOR was found in fingers and palm in long cue-target SOA. Also we observed a 'Cue above Target' effect (facilitation effect when the Cue had appeared distal to the target location in a vertical line) at the long SOA. Together, we suggest that the general pattern of results supports the proposed hypothesis about the different mental representation of fingers and palms, but with a considerable and hierarchical interrelation between them.

Differential consequences of orienting attention in parallel and serial search: an ERP study

Previous research has linked attentional effects (such as inhibition of return; IOR) to serial visual search. We investigated different modes of visual search (serial vs. parallel) and demonstrated that the attentional set induced by the type of search greatly influences these attentional effects. IOR was linked to serial search while facilitation followed parallel search. Event related potentials and LORETA source localization data demonstrated that facilitation was associated with a single component, localized in the cuneus and precuneus, while IOR was related to three different components, involving the superior parietal lobe (at around 200 ms), the anterior cingulate cortex and bilateral medial frontal gyrus (~240 ms), and the bilateral superior temporal gyrus, supramarginal gyrus and inferior parietal gyrus (~280 ms). Our results are consistent with the notion that attentional set determines spatial orienting and with previous studies proposing that IOR is not observed in all previously attended locations.

Inhibition of Return Exaggerates Change Blindness

Peripheral cues trigger attention shifts, which facilitate perceptual processing and enhance visual awareness. However, this facilitation is superseded by an inhibition of return (IOR) effect, which biases attention away from the cued location. While the link between facilitatory effects of visual attention and awareness is well established, no study has reported negative effects of spatial cueing on visual awareness. This failure is puzzling, given the claim that attention is a necessary precondition for awareness. If attention is necessary for awareness, inhibiting attention should also inhibit awareness. This leads to a slightly counterintuitive prediction: Spatial cueing will inhibit awareness at long cue–target latencies. This study shows that subliminal peripheral cues exaggerate change blindness at long cue–change latencies, demonstrating that IOR can suppress visual awareness of changes and suggesting that IOR can directly affect the contents of consciousness.

Lesion of primary visual cortex in monkey impairs the inhibitory but not the facilitatory cueing effect on saccade

Prior visual stimulus presentation induces immediate facilitation and subsequent inhibition of orienting to an ensuing target at the same location. Recent studies revealed that the superior colliculus (SC) is involved in these facilitatory and inhibitory cueing effects on saccade; however, as the SC receives inputs both directly from the retina (retino-tectal pathway) and indirectly from visual cortices (geniculostriate pathway), it is unclear which visual pathway contributes to the effects. We investigated this issue using monkeys with lesions in the primary visual cortex (V1), thus depriving the SC of the geniculostriate pathway and leaving the retino-tectal pathway intact. We found that the inhibitory cueing effect was selectively impaired and the facilitatory cueing effect was spared after V1 lesions. The results suggest that the geniculostriate and the retino-tectal pathways are differentially involved in the generation of cueing effects on saccade: The former is critically involved in the inhibitory effect whereas the latter alone can induce the facilitatory effect. The results provide the first direct evidence for the involvement of the geniculostriate pathway in the inhibitory cueing effect and further imply that the more recent evolution of the geniculostriate pathway in higher mammals improves the efficiency of visual search by inhibiting orienting to a previously attended location.

Attentional capture and trait anxiety: evidence from inhibition of return

Attentional biases regarding attentional capture by threat-related stimuli in anxious people were investigated by using a standard spatial cueing procedure suitable to measure inhibition of return (IOR). In two experiments, participants categorized the emotional valence of either emotional (positive and negative words) or non-emotional (neutral words in both experiments and sets of 'xxx' in Experiment 1) targets that were preceded by a peripheral non-predictive cue. The typical IOR effect (slower responses for words presented at previously cued locations) was observed for non-emotional and positive stimuli, with similar results being observed for both low and high trait anxiety groups. For negative stimuli, however, the high trait anxiety group did not show the IOR effect, while it was present in the low trait anxiety group. This general pattern of results suggests that, in individual with high trait anxiety, threatening stimuli can capture attention at the locations whether attentional capture is hindered by other cognitive effects such as IOR.

Motor set modulates automatic priming effects of uninformative cues

In a series of three experiments, we examined facilitatory and inhibitory effects of uninformative spatial cues in a four-choice reaction time (RT) task that required three different types of responses: detection, reaching, and keypressing. Results revealed a pattern of facilitation and inhibition that strongly depended on response mode: Whereas detection and reaching showed longer RTs for cued than uncued locations (reflecting inhibition of return), keypress responses showed shorter RTs for cued than uncued locations (reflecting automatic response activation). Together, these results provide converging evidence for the Grouping model of precuing effects [Adam, J. J., Hommel, B., & Umiltà, C. (2003). Preparing for perception and action (I): The role of grouping in the response-cuing task. Cognitive Psychology, 46, 302-358; Adam, J. J., Hommel, B., & Umiltà, C. (2005). Preparing for perception and action (II): Automatic and effortful processes in response-cuing. Visual Cognition, 12, 1444-1473].

Left visual neglect: is the disengage deficit space- or object-based?

Attention can be directed to spatial locations or to objects in space. Patients with left unilateral spatial neglect are slow to respond to a left-sided target when it is preceded by a right-sided "invalid" cue, particularly at short cue-target intervals, suggesting an impairment in disengaging attention from the right side in order to orient it leftward. We wondered whether this deficit is purely spatial, or it is influenced by the presence of a right-sided visual object. To answer this question, we tested 10 right brain-damaged patients with chronic left-neglect and 41 control participants on a cued response time (RT) detection task in which targets could appear in either of two lateral boxes. In different conditions, non-informative peripheral cues either consisted in the brightening of the contour of one lateral box (onset cue condition), or in the complete disappearance of one lateral box (offset cue condition). The target followed the cue at different stimulus-onset asynchronies (SOAs). If the disengagement deficit (DD) is purely space-based, then it should not vary across the two cueing conditions. With onset cues, patients showed a typical DD at short SOAs. With offset cues, however, the DD disappeared. Thus, patients did not show any DD when there was no object from which attention must be disengaged. These findings indicate that the attentional bias in left-neglect does not concern spatial locations per se, but visual objects in space.

Temporal dynamics of attentional control settings in patients with spatial neglect

Patients with spatial neglect show disproportionately slow reactions to a contralesional stimulus presented shortly after an ipsilesional cue. We examined whether this attentional bias reflects purely automatic capture of attention by the cue or whether it is contingent on the similarity between cue and target. Patients with spatial neglect reacted to letters presented in the left or right visual field. These target letters were pre-cued by the same letter (similar cue) or a different letter (dissimilar cue) presented 100 or 1000 ms prior to target onset in the same or the opposite visual field. At the short interval, similar and dissimilar ipsilesional cues captured attention comparably and strongly slowed reactions to contralesional targets. In contrast, while similar ipsilesional cues still captured attention at the long interval dissimilar cues ceased to affect performance. In contrast, the different cueing conditions induced only small and insignificant differences in reaction times to ipsilesional targets. These findings suggest that attention of neglect patients is initially captured by all ipsilesional cues in a reflexive, stimulus-driven fashion, but that prolonged attentional capture may only be observed when cues share a property with the target.

Intentional control of attention: action planning primes action-related stimulus dimensions

Neurophysiological observations suggest that attending to a particular perceptual dimension, such as location or shape, engages dimension-related action, such as reaching and prehension networks. Here we reversed the perspective and hypothesized that activating action systems may prime the processing of stimuli defined on perceptual dimensions related to these actions. Subjects prepared for a reaching or grasping action and, before carrying it out, were presented with location- or size-defined stimulus events. As predicted, performance on the stimulus event varied with action preparation: planning a reaching action facilitated detecting deviants in location sequences whereas planning a grasping action facilitated detecting deviants in size sequences. These findings support the theory of event coding, which claims that perceptual codes and action plans share a common representational medium, which presumably involves the human premotor cortex.