Search

Background: Despite being one of the direct causes of depression, whether stroke-induced neuroanatomical deterioration actually plays an important role in the onset of poststroke depression (PSD) is controversial. We assessed the structural basis of PSD, particularly with regard to white matter connectivity. Methods: We evaluated lesion index, fractional anisotropy (FA) reduction and brain structural networks and then analyzed whole brain voxel-based lesions and FA maps. To understand brain damage in the context of brain connectivity, we used a graph theoretical approach. We selected nodes whose degree correlated with the Hamilton Rating Scale for Depression score (p < 0.05, false discovery rate-corrected), after controlling for age, sex, years of education, lesion size, Mini Mental State Examination score and National Institutes of Health Stroke Scale score. We used Poisson regression with robust standard errors to assess the contribution of the identified network toward poststroke major depression. Results: We included 116 stroke patients in the study. Fourteen patients (12.1%) had diagnoses of major depression and 26 (22.4%) had mild depression. We found that lesions in the right insular cortex, left putamen and right superior longitudinal fasciculus as well as FA reductions in broader areas were all associated with major depression. Seventeen nodes were selected to build the depression-related subnetwork. Decreased local efficiency of the subnetwork was a significant risk factor for poststroke major depression (relative risk 0.84, 95% confidence interval 0.72-0.98, p = 0.027). Limitations: The inability of DTI tractography to process fibre crossings may have resulted in inaccurate construction of white matter networks and affected statistical findings. Conclusion: The present study provides, to our knowledge, the first graph theoretical analysis of white matter networks linked to poststroke major depression. These findings provide new insights into the neuroanatomical substrates of depression that develops after stroke., Introduction Poststroke depression (PSD) is one of the most common emotional disorders afflicting those who experience stroke. A meta-analysis has indicated that the prevalence of major or mild depression is [...]

We examined two forms of top-down effects on visual selection: (1) information held in working memory (WM) and (2) the semantic relations between targets and distractors. We found that items held in WM affected search for a different target. This WM-based interference effect generalized across different exemplars, even though participants could remember the specific exemplar on the trial. This argues against a memory top-up account of performance. In addition, there was interference from distractors that were not held in WM but were semantically related to the target. The effects of WM capture and the effects of capture by a distractor related to the target combined additively. The data suggest that task-irrelevant information in WM and task-relevant templates for targets compete separately for selection. The implications for understanding top-down processes in search are discussed. doi: 10.3758/MC.38.8.1058

Four experiments examined the effects of precues on visual search for targets defined by a color-orientation conjunction. Experiment 1 showed that cueing the identity of targets enhanced the efficiency of search. Cueing effects were stronger with color than with orientation cues, but this advantage was additive across array size. Experiment 2 demonstrated that cueing effects interacted with bottom-up segmentation processes, whereas Experiment 3 showed the stronger effects of color cues remained in a compound task. Experiment 4 confirmed the enhanced effect of color cueing even when verbal rather than visual cues were used. The targets used were balanced for search efficiency within both orientation and color dimensions. We suggest search benefits from the top-down cueing of color compared with orientation because color cueing enhances the segmentation of displays into color groups more efficiently. This enables search to an appropriate color group to be initiated earlier. We discuss how top-down segmentation processes interact with differences in bottom-up segmentation to further improve target detection. Keywords: visual attention, conjunction search, cueing, color, orientation DOI: 10.1037/a0017179

We demonstrate that right-handed participants make speeded classification responses to pairs of objects that appear in standard co-locations for right-handed actions relative to when they appear in reflected locations. These effects are greater when participants 'weight' information for action when deciding if 2 objects ate typically used together, compared with deciding if objects typically occur in a given context. The effects are enhanced, and affect both types of decision, when an agent is shown holding the objects. However, the effects are eliminated when the objects are not viewed from the first-person perspective and when words are presented rather than objects. The data suggest that (a) participants ate sensitive to whether objects are positioned correctly for their own actions, (b) the position information is coded within an egocentric reference frame, (c) the critical representation involved is visual and not semantic, and (d) the effects are enhanced by a sense of agency. The results can be interpreted within a dual-route framework for action retrieval in which a direct visual route is influenced by affordances for action. Keywords: dual routes to action, action decisions, contextual decisions, object affordance, first- or third-person perspective DOI: 10.1037/a0017175

Perception and action are influenced by the 'possibilities for action' in the environment. Neuropsychological studies (e.g., Riddoch, Humphreys, Edwards, Baker, & Willson, 2003) have demonstrated that objects that are perceived to be interacting (e.g., a corkscrew going toward the top of a wine bottle) are perceptually integrated into a functional unit, facilitating report of both objects. In addition, patients with parietal damage tend to report the 'active' item of the pair (the corkscrew in the above example) when the objects are positioned for action, overriding their spatial bias toward the ipsilesional side. Using a temporal order judgment task we show for the first time that normal viewers judge that active objects appear earlier when they are positioned correctly for action. This effect is not dependent on a learned relationship between objects, or on the active object being integrated at a perceptual level with the object it is paired with. The data suggest that actions afforded by a correctly positioned active object permeate normal perceptual judgments. Keywords: action, affordance, perception, temporal order judgments DOI: 10.1037/a0018739

Two experiments are reported that use patients with visual extinction to examine how visual attention is influenced by action information in images. In Experiment 1 patients saw images of objects that were either correctly or incorrectly colocated for action, with the objects held by hands that were congruent or incongruent with those used premorbidly by the patients. The images were also shown from a 1st- and 3rd-person perspective. There was an overall reduction in extinction for objects colocated for action. In addition, there was ah extra benefit when the objects were held in hands congruent with those used by the patients and when the objects were seen from a 1st-person perspective. This last result fits with an effect of motor simulation, over and above a purely visual effect based on positioning objects correctly for action. Experiment 2 showed that effects of hand congruence could emerge with images depicted from a 3rd-person perspective when patients saw themselves holding the objects. The data indicate 2 effects of action information on extinction: (a) an effect of colocating objects for action, which does not depend on a self-reference frame (a visual effect), and (b) an effect sensitive to object-hand congruence, which does depend on a self-reference frame (a motor-based effect). The self-reference frame is induced when stimuli are viewed from a 1st-person perspective and when an image of the self is seen from a 3rd-person perspective. Both visual and motor-based effects of action information facilitate the spread of attention across objects. Keywords: affordance, effects of action relation, visual attention, visual extinction DOI: 10-1037/a001.317

Evidence that show how visual attention is strongly controlled by an object's potential for action is discussed. The evidence supports the argument that visual selection began as a need to prioritize objects for action.

We show that perceptual sensitivity to visual stimuli can be modulated by matches between the contents of working memory (WM) and stimuli in the visual field. Observers were presented with an object cue (to hold in WM or to merely attend) and subsequently had to identify a brief target presented within a colored shape. The cue could be re-presented in the display, where it surrounded either the target (on valid trials) or a distractor (on invalid trials). Perceptual identification of the target, as indexed by A', was enhanced on valid relative to invalid trials but only when the cue was kept in WM. There was minimal effect of the cue when it was merely attended and not kept in WM. Verbal cues were as effective as visual cues at modulating perceptual identification, and the effects were independent of the effects of target saliency. Matches to the contents of WM influenced perceptual sensitivity even under conditions that minimized competition for selecting the target. WM cues were also effective when targets were less likely to fall in a repeated WM stimulus than in other stimuli in the search display. There were no effects of WM on decisional criteria, in contrast to sensitivity. The findings suggest that reentrant feedback from WM can affect early stages of perceptual processing. Keywords: working memory, perception, attention, signal detection DOI: 10.1037/a0018686

The authors present neuropsychological evidence distinguishing binding between form, color, and size (cross-domain binding) and binding between form elements. They contrasted conjunctive search with difficult feature search using control participants and patients with unilateral parietal or fronto/temporal lesions. To rule out effects of task difficulty or loss of top-down guidance of search, the authors made conjunction search easier than feature search. Despite this, parietal patients were selectively impaired at detecting conjunction targets in their contralateral field. In contrast, the parietal patients performed like the other participants with form conjunctions, with form conjunctions being easier to detect than difficult feature targets. These data indicate a qualitative difference between binding in the form domain and binding across form, color, and size, consistent with theories that propose distinct binding processes in vision. Keywords: visual binding, parietal lesions, conjunction and feature search

During the past 20 years there has been much research into the factors that modulate awareness of contralesional information in neurological patients with visual neglect or extinction. However, the potential role of the individual's emotional state in modulating awareness has been largely overlooked. In the current study, we induced a pleasant and positive affective response in patients with chronic visual neglect by allowing them to listen to their pleasant preferred music. We report that the patients showed enhanced visual awareness when tasks were performed under preferred music conditions relative to when tasks were performed either with unpreferred music or in silence. These results were also replicated when positive affect was induced before neglect was tested. Functional MRI data showed enhanced activity in the orbitofrontal cortex and the cingulate gyrus associated with emotional responses when tasks were performed with preferred music relative to unpreferred music. Improved awareness of contralesional (left) targets with preferred music was also associated with a strong functional coupling between emotional areas and attentional brain regions in spared areas of the parietal cortex and early visual areas of the right hemisphere. These findings suggest that positive affect, generated by preferred music, can decrease visual neglect by increasing attentional resources. We discuss the possible roles of arousal and mood in generating these effects. attention | brain damage | neuropsychology | positive affect | vision

We examined the contributions of the human pulvinar to goal directed selection of visual targets in 3 patients with chronic, unilateral lesions involving topographic maps in the ventral pulvinar. Observers completed 2 psychophysical tasks in which they discriminated the orientation of a lateralized target grating in the presence of vertically-aligned distracters. In experiment 1, where distracter contrast was varied while target contrast remained constant, the patients' contralesional contrast thresholds for discriminating the orientation of grating stimuli were elevated only when the task required selection of a visual target in the face of competition from a salient distracter. Attentional selectivity was restored in the patients in experiment 2 where target contrast was varied while distracter contrast remained constant. These observations provide the first evidence that the human pulvinar plays a necessary role in modulating physical saliency in attentional selection, and supports a homology in global puivinar structure between humans and monkey. salience | visual attention

There is strong evidence that developments in children's theory of mind (TOM) at 3-4 years are related to developments in language and executive function. However, these relationships might exist for 2 reasons. First, language and executive function might be necessary for the mature ToM abilities that children are in the process of developing. Second, language and executive function may be necessary for developing ToM but have no necessary role in mature ToM. It is difficult to distinguish between these possibilities if researchers only study young children. Studies of adults can provide direct evidence about the role of language and executive function in mature ToM. Recent work suggests that impaired executive function has multiple roles in adult ToM but that severely impaired grammar can leave ToM structurally intact. While studies of children report that ToM correlates with both language and executive function, findings from adults suggest that these relationships should be interpreted in importantly different ways. Keywords: theory of mind, executive function, adults, false belief, language

The essential issue rose by Kingstone and collegue's contribution that emphasizes the trade off between experimental control and naturalness in cognitive psychology and cognitive neuroscience is discussed.

Two experiments were conducted with younger and older speakers. In Experiment 1, participants named single objects that were intact or visually degraded, while hearing distractor words that were phonologically related or unrelated to the object name. In both younger and older participants naming latencies were shorter for intact than for degraded objects and shorter when related than when unrelated distractors were presented. In Experiment 2, the single objects were replaced by object triplets, with the distractors being phonologically related to the first object's name. Naming latencies and gaze durations for the first object showed degradation and relatedness effects that were similar to those in single-object naming. Older participants were slower than younger participants when naming single objects and dower and less fluent on the second but not the first object when naming object triplets. The results of these experiments indicate that both younger and older speakers plan object names sequentially, but that older speakers use this planning strategy less efficiently.

To purchase or authenticate to the full-text of this article, please visit this link: http://dx.doi.org/10.1111/j.1467-9280.2008.02132.x Byline: Suzanne Higgs (1), Amy C. Williamson (1), Pia Rotshtein (1), Glyn W. Humphreys (1) Abstract: ABSTRACT What is the relationship between memory and appetite? We explored this question by examining preferences for recently consumed food in patients with amnesia. Although the patients were unable to remember having eaten, and were inclined to eat multiple meals, we found that sensory-specific satiety was intact in these patients. The data suggest that sensory-specific satiety can occur in the absence of explicit memory for having eaten and that impaired sensory-specific satiety does not underlie the phenomenon of multiple-meal eating in amnesia. Overeating in amnesia may be due to disruption of learned control by physiological aftereffects of a recent meal or to problems utilizing internal cues relating to nutritional state. Author Affiliation: (1)University of Birmingham Article History: (R eceived 6/4/07; R evision accepted 12/21/07) Article note: Address correspondence to Suzanne Higgs, University of Birmingham, Edgbaston, Birmingham, B15 2TT, England, e-mail: s.higgs.1@bham.ac.uk.

The ability to report the temporal order of 2 tactile stimuli (1 applied to each hand) has been shown to decline when the arms are crossed over compared with when they are uncrossed. However, these effects have only been measured when temporal order was reported by stimulus location. It is unknown whether this spatial manipulation of the body affects all tactile temporal order judgments (TOJs) or only those judgments that are spatially defined. The authors examined the effect of crossing the arms on tactile TOJs when stimuli were identified by either spatial (location) or nonspatial (frequency or duration) attributes. Spatial TOJs were significantly impaired when the arms were in crossed compared with uncrossed postures, but there was no effect of posture when order was judged by nonspatial attributes. Taskdependent modulation of the effects of posture was also evident when response complexity was reduced to go/no-go responses. These results suggest that crossing the arms impairs tactile localization and thus spatial TOJs. However, the data also suggest that localization is not a necessary precursor when temporal order can be computed by nonspatial means. Keywords: tactile, temporal order, spatial, posture

The ability to attend to relevant events and to ignore irrelevant stimuli is crucial to survival. Theories disagree on whether this ability is dependent solely on increased neural activation for relevant items or whether active ignoring can also play a role. The authors examined the active ignoring of stimuli using a preview search procedure, where irrelevant faces appeared prior to relevant house stimuli. They found increased activation in brain regions associated with spatial memory and in content-specific faceprocessing areas when participants ignored the irrelevant faces. Differences arose even on trials when only previewed faces appeared, and the magnitude of these differences predicted how well faces were ignored in search. Activation associated with active ignoring decreased when a secondary task was imposed during the preview. The data reveal a neural marker for the process of actively ignoring the content and locations of irrelevant stimuli. Keywords: preview search, fMRI, marking, inattention

In 2 experiments, the authors explored age of acquisition (AoA) and word frequency (WF) effects in picture naming using the psychological refractory period paradigm. In Experiment 1, participants named a picture and then, a short time later, categorized 1 of 3 possible auditory tones as high, medium, or low. Both AoA (Experiment IA) and WF (Experiment 1B) effects propagated onto tone discrimination reaction times (RTs), with the effects of AoA being stronger. In Experiment 2, the to-be-named picture followed the auditory tone by a varying interval. As the interval decreased, picture naming RTs increased. The relationship between the interval and AoA (Experiment 2A) was reliably underadditive; AoA effects were eliminated at the shortest interval. In contrast, WF (Experiment 2B) was additive with the effects of the interval. These results demonstrate an empirical dissociation between AoA and WF effects. AoA affects processing stages that precede those that are sensitive to WF. The implications for theories of picture naming are discussed. Keywords: age of acquisition, frequency, psychological refractory period, picture naming

To purchase or authenticate to the full-text of this article, please visit this link: http://dx.doi.org/10.1111/j.1467-9280.2008.02044.x Byline: Sara Forti (1,2), Glyn W. Humphreys (1) Abstract: ABSTRACT We contrasted visual search for targets presented in prototypical views and targets presented in nonprototypical views, when targets were defined by their names and when they were defined by the action that would normally be performed on them. The likelihood of the first fixation falling on the target was increased for prototypical-view targets falling in the lower visual field. When targets were defined by actions, the durations of fixations were reduced for targets in the lower field. The results are consistent with eye movements in search being affected by representations within the dorsal visual stream, where there is strong representation of the lower visual field. These representations are sensitive to the familiarity or the affordance offered by objects in prototypical views, and they are influenced by action-based templates for targets. Author Affiliation: (1)Behavioural Brain Sciences Centre, School of Psychology, University of Birmingham (2)Neuropsychology Unit, IRCCS 'Eugenio Medea,' Bosisio Parini, Italy Article History: (R eceived 4/24/07; R evision accepted 6/3/07) Article note: Address correspondence to Glyn W. Humphreys, Behavioural Brain Sciences Centre, School of Psychology, University of Birmingham, Birmingham B15 2TT, United Kingdom, e-mail: g.w.humphreys@bham.ac.uk.

Visual selection is influenced by items in working memory (WM) and priming from implicit memory when a stimulus is repeated across time. WM effects are typically held to be top-down in nature [Soto D, Heinke D, Humphreys GW, Blanco MJ (2005) J Exp Psychol Hum Percept Perform 31:248-261], whereas implicit priming may operate in a bottom-up manner [Theeuwes J, Reimann B, Mortier K (2006) Vis Cogn 14: 466-489]. How WM and implicit priming affects influence visual selection remains poorly understood, however. Here, we report functional MRI evidence that dissociates the neural mechanisms involved in these memory-based effects on selection. The reappearance of a stimulus held in WM enhanced activity in superior frontal gyrus, midtemporal, and occipital areas that are known to encode the prior occurrence of stimuli. In contrast, mere stimulus repetition elicited a suppressive response in the same regions. An additional finding was that a frontothalamic network was sensitive to the behavioral relevance of a match between the contents of WM and the visual search array, enhancing activity when the contents of WM matched the critical target of selection. Items held in WM influence selection by using neural coding distinct to effects of mere repetition. repetition priming | working memory | fMRI | anterior prefrontal cortex: BA10 | thalamus

Evidence is presented for 2 modes of attention operating in simultanagnosia. The authors examined visual enumeration in a patient, GK, who has severe impairments in serially scanning across a scene and is unable to count the numbers of items in visual displays. However, GK's ability to judge the relative magnitude of 2 displays was consistently above chance, even when overall luminosity did not vary with the number of items present. In addition, several variables had a differential impact on GK's counting and magnitude estimation. Magnitude estimation but not counting was facilitated by using elements that grouped more easily and by presenting the elements in regular configurations. In contrast, counting was facilitated by placing the elements in different colors while magnitude estimation was disrupted. Also GK's performance on magnitude estimation tasks was disrupted by asking him to count the elements present. The data suggest that GK can process visual stimuli in either a focused or distributed attention mode. When in a focused attention mode, performance is limited by poor serial scanning of attention due to an impaired explicit representation of visual space. Keywords: counting, estimating, numerosity, neuropsychology, distributed attention

Previous studies have shown that visual attention can be captured by stimuli matching the contents of working memory (WM). Here, the authors assessed the nature of the representation that mediates the guidance of visual attention from WM. Observers were presented with either verbal or visual primes (to hold in memory, Experiment 1; to verbalize, Experiment 2; or merely to attend, Experiment 3) and subsequently were required to search for a target among different distractors, each embedded within a colored shape. In half of the trials, an object in the search array matched the prime, but this object never contained the target. Despite this, search was impaired relative to a neutral baseline in which the prime and search displays did not match. An interesting finding is that verbal primes were effective in generating the effects, and verbalization of visual primes elicited similar effects to those elicited when primes were held in WM. However, the effects were absent when primes were only attended. The data suggest that there is automatic encoding into WM when items are verbalized and that verbal as well as visual WM can guide visual attention. Keywords: working memory, visual attention, visual search, top-down processing

The authors report 4 experiments that examined color grouping and negative carryover effects in preview search via a probe detection task (J. J. Braithwaite, G. W. Humphreys, & J. Hodsoll, 2003). In Experiment 1, there was evidence of a negative color carryover from the preview to new items, using both search and probe detection measures. There was also a negative bias against probes on old items that carried the majority color in the preview. With a short preview duration (150 ms) carryover effects to new items were greatly reduced, but probe detection remained biased against the majority color in the old item. Experiments 2 and 4 showed that the color bias effects on old items could be reduced when these items had to be prioritized relative to being ignored. Experiment 3 tested and rejected the idea that variations in the probability of whether minority or majority colors were probed were crucial. These results show that the time course of color carryover effects can be separated from effects of early color grouping in the preview display: Color grouping is fast, and inhibitory color carryover effects are slow. Keywords: visual selective attention, attentional guidance, color grouping, inhibition, time effects

A central bias in spatial selection has been proposed to explain the decreasing search efficiency with increasing target eccentricity that results when distractors can occur closer to fixation than the target (J. M. Wolfe, P. O'Neill, & S. C. Bennett, 1998). The authors found evidence for such a bias using an odd-man-out variant of conjunction search. However, the bias was absent for the same displays when the identity of the odd-man-out target was known in advance. The authors propose that (a) top-down knowledge of a target feature supports grouping on this feature and (b) grouping links a peripheral target to central distractors expressing the same feature, increasing the attentional weighting afforded to the target and, consequently, facilitating its detection. The effects are independent of bottom-up priming effects occurring across trials. Thus, feature-based grouping can be driven top-down and can overrule the central bias in spatial selection. Keywords: attention, grouping, eccentricity, search, top-down

This article reports evidence that two variables--object viewpoint and semantic priming--differentially affect action and semantic decisions to objects. Changing the viewing angle of an object, so that its graspable parts are oriented away from observers, disrupted action decisions hut had little effect on semantic categorization. In contrast, semantic priming influenced semantic categorization and object naming, but not action decisions. Action priming, however, did not affect performance. These selective effects are consistent with the existence of separate semantic and direct (nonsemantic) routes to action from vision.

Visual search in a conjunction task can be facilitated if half the distractor items are previewed prior to the other half of the distractors and the target item. Here, we investigate the nature of this preview by using a top-up procedure, which presents an initial preview followed by a secondary preview after a period of time (the offset period). In Experiment 1, we demonstrate that increasing the time of the offset period decreases search efficiency. If the offset period is increased to 2 sec, the previewed items are searched to a greater extent than when the offset period is 450 msec. This holds even when the old items remain in the same positions across presentations and when they differ in color from new search stimuli. However, when the offset intervals are reduced, the preview can be discounted from search even when the old items change locations between exposures (Experiment 2) and when they are not distinguished from search displays by their color (Experiment 3). The last result occurs only as long as the preview items can be grouped in terms of form. When the preview stimuli are heterogeneous, they are no longer discounted from search if their locations change across the offset period (Experiment 4). We interpret the data in terms of object-based priming, which enables the repeated form of the old distractors to be filtered more easily from search.

In the present study, we demonstrate that parietal patients with visual extinction show enhanced awareness when there is a match between the current contents of their working memory and the stimuli presented in the visual field. This effect cannot be attributed to automatic bottom-up priming from the presentation of a memory cue, because extinction was reduced only when patients committed the cue to memory, and not when primes were viewed passively or merely identified. The results suggest that reentrant processes, from working memory, modulate awareness. top-down processing | parietal damage | attention

We investigated the effect of contextual cuing (M. M. Chun & Y. Jiang, 1998) within the preview paradigm (D. G. Watson & G. W. Humphreys, 1997). Contextual cuing was shown with a 10-item letter search but not with more crowded 20-item displays. However, contextual learning did occur in a preview procedure in which 10 preview items were followed by 10 new items. Repeating the new items alone did not generate contextual learning, but repeating the preview items alone did, as long as they had a consistent spatial relation with the target. This was not merely due to the onset of the preview items being associated with the target location. No learning effect took place with a preview of homogeneous items that competed less for selection with new stimuli. The results provide evidence for old items being processed in preview search and providing a context for subsequent search of new items. Keywords: visual search, preview search, contextual cuing

We report three experiments in which name verification responses to either objects (Experiments 1 and 2) or hand movements (Experiment 3) were compared with action decisions, where participants verified whether an object is typically used in the way described by a verbal label. In Experiments 1 and 2, we report that action decisions show more consistent and larger effects of the congruency of either a handgrip or a type of movement than do name verification responses, although there was some effect of the congruency of the handgrip on name verification. In Experiment 3, we demonstrate that the congruency of the object being moved affects both action and name verification responses to hand movements. We discuss the data relative to accounts of how actions and names are accessed by visually presented objects and in relation to work on the information called upon in classification tasks.

Previous studies have shown that spatial attention can shift in three-dimensional (3-D) space determined by binocular disparity: Using Posner's precueing paradigm, the current work examined whether attentional selection occurs in perceived 3-D space defined by occlusion. Experiment 1 showed that shifts of spatial attention induced by central cues between two surfaces in the left and right visual fields did not differ between the conditions when the two surfaces were located at the same or different perceptual depth. In contrast, Experiment 2 found that peripheral cues generated a stronger cue validity effect when the two surfaces were perceived at a different rather than at the same perceptual depth. The results suggest that exogenous but not endogenous attention operates in perceived 3-D space.

Four experiments explored the interrelations between working memory, attention, and eye movements. Observers had to identify a tilted line amongst vertical distractors. Each line was surrounded by a colored shape that could be precued by a matching item held in memory. Relative to a neutral baseline, in which no shapes matched the memory item, search was more efficient when the memory cue matched the shape containing the target, and it was less efficient when the cued stimulus contained a distractor. Cuing affected the shortest reaction times and the first saccade in search. The effect occurred even when the memory cue was always invalid but not when the cue did not have to be held in memory. There was also no evidence for priming effects between consecutive trials. The results suggest that there can be early, involuntary top-down directing of attention to a stimulus matching the contents of working memory.

The authors studied the influence of canonical orientation on visual search for object orientation. Displays consisted of pictures of animals whose axis of elongation was either vertical or tilted in their canonical orientation. Target orientation could be either congruent or incongruent with the object's canonical orientation. In Experiment 1, vertical canonical targets were detected faster when they were tilted (incongruent) than when they were vertical (congruent). This search asymmetry was reversed for tilted canonical targets. The effect of canonical orientation was partially preserved when objects were high-pass filtered, but it was eliminated when they were low-pass filtered, rendering them as unfamiliar shapes (Experiment 2). The effect of canonical orientation was also eliminated by inverting the objects (Experiment 3) and in a patient with visual agnosia (Experiment 4). These results indicate that orientation search with familiar objects can be modulated by canonical orientation, and they indicate a top-down influence on orientation processing.

The mechanisms underlying segmentation and selection of visual stimuli over time were investigated in patients with posterior parietal damage. In a modified visual search task, a preview of old objects preceded search of a new set for a target while the old items remained. In Experiment 1, control participants ignored old and prioritized new items, but patients had severe difficulties finding the target (especially on the contralesional side). In Experiment 2, simplified displays yielded analogous results, ruling out search ease as a crucial factor in poor preview search. In Experiment 3, outlines around distractor groups (to aid segmentation) improved conjunction but not preview search, suggesting a specific deficit in spatiotemporal segmentation. Experiment 4 ruled out spatial disengagement problems as a factor. The data emphasize the role of spatiotemporal segmentation cues in preview search and the parietal lobe in the role of these cues to prioritize search of new stimuli.

Search for a colour-form conjunction target can be facilitated by presenting one set of distractors prior to the second set of distractors and the target: the preview benefit (Watson & Humphreys, 1997). The early presentation of one set of distractors enables them to be efficiently filtered from search. We report two studies investigating the time course of the preview benefit. In Experiment 1 we use a standard reaction time analysis to show that the benefit has a relatively slow time course; old items need to precede the new set by 600 ms or more in order to be fully filtered from search. Furthermore, the reductions in reaction time across time in the preview condition varied nonlinearly with the display size, suggesting that old items were discounted from search in parallel. In Experiment 2 we examined the neural locus of this filtering effect over time, using positron emission tomography (PET). We show that regions of parieto-occipital cortex are selectively activated in a preview search condition relative to a detection baseline. These regions also increase in activation as the preview interval increases (and search then becomes easier), consistent with them modulating the parallel filtering of distractors from targets in spatial search. Interestingly, the same areas as those activated in preview search were also active in conjunction search relative to its own detection baseline. Thus these regions either modulate parallel filtering in conjunction search too, or they modulate different behavioural functions according to task constraints.

It has previously been shown that when picture pairs are repeated across blocks in a post-cue naming task, former distractors are named faster than former targets: the 'negative repetition effect' (Mayall,Humphreys, & Kotsanis, 2002). In the present study the time course of this effect was examined. Experiment 1 demonstrated that the effect became apparent after a lag of only two intervening trials, with former targets being named faster than former distractors after a lag of zero trials. Experiment 2 used a new baseline condition with repeated picture pairs for which no response was required on the first presentation. Comparisons with this baseline indicated that the negative repetition effect is the result of suppression of former targets as opposed to facilitation of former distractors. The results support the proposal of Mayall et al. that the negative repetition effect reflects a form of speech monitoring that is applied when there is competition in the process of mapping from semantics to name representations.

Three experiments examined nonspatial extinction in G.K., a patient with bilateral parietal damage. Experiment 1 demonstrated nonspatial extinction (poor detection of a weak relative to a stronger perceptual group), even when the stronger group was less complex than the weaker group. Experiment 2 showed improved report of a letter falling at the location of the stronger group, but explicit judgments of the location of the letter were at chance. Experiment 3 replicated the object-cuing benefit, though G.K. could not discriminate whether a letter fell at the same location as the stronger perceptual group. The data indicate coupling between object- and space-based attention, so that spatial attention is drawn to the location occupied by the winner of object-based competition for selection. In this case, what cues where. This coupling operates implicitly, even when explicit location judgments are impaired.

Preview search with moving stimuli was investigated. The stimuli moved in multiple directions, and preview items could change either their color or their shape before onset of the new (search) displays. In Experiments 1 and 2, the authors found that (a) a preview benefit occurred even when more than 5 moving items had to be ignored, and (b) color change, but not shape change, disrupted preview search in moving stimuli. In contrast, shape change, but not color change, disrupted preview search in static stimuli (Experiments 3 and 4). Results suggest that preview search with moving displays is influenced by inhibition of a color map, whereas preview search with static displays is influenced by inhibition of locations of old distractors.

Five experiments addressed the role of color grouping in preview search (D. G. Watson & G. W. Humphreys, 1997). Experiment 1 used opposite color ratios of distractors in preview and second search displays, creating equal numbers of distractors in each color group in the final display. There was selective slowing for new targets carrying the majority color of the old items. This effect held when there was no bias in the preview and only the second search set had an uneven color ratio (Experiment 2). In Experiment 3, participants had foreknowledge of the target color, and effects were shown over and above those due to color biases. Experiment 4 demonstrated negative color carryover even when previews changed color. Experiment 5 showed reduced color carryover effects when previews were presented more briefly. Collectively, the results provide evidence for inhibitory carryover effects in preview search based on feature grouping.

In the 'Thatcher illusion' a face, in which the eyes and mouth are inverted relative to the rest of the face, looks grotesque when shown upright but not when inverted. In four experiments we investigated the contribution of local and global processing to this illusion in normal observers. We examined inversion effects (i.e., better performance for upright than for inverted faces) in a task requiring discrimination of whether faces were or were not 'thatcherized'. Observers made same/different judgements to isolated face parts (Experiments 1-2) and to whole faces (Experiments 3-4). Face pairs had the same or different identity, allowing for different processing strategies using feature-based or configural information, respectively. In Experiment 1, feature-based matching of same-person face parts yielded only a small inversion effect for normal face parts. However, when feature-based matching was prevented by using the face parts of different people on all trials (Experiment 2) an inversion effect occurred for normal but not for thatcherized parts. In Experiments 3 and 4, inversion effects occurred with normal but not with thatcherized whole faces, on both same- and different-person matching tasks. This suggests that a common configural strategy was used with whole (normal) faces. Face context facilitated attention to misoriented parts in same-person but not in different-person matching. The results indicate that (1) face inversion disrupts local configural processing, but not the processing of image features, and (2) thatcherization disrupts local configural processing in upright faces.

Evidence that salient feature singletons guide attention only when the target and the singleton frequently coincide has been taken to suggest that selection of singletons is under top-down control: Observers strategically use an attentional set sensitive to the singleton being a target. Changing the singleton-target (or singleton-distractor) coincidence also changes the opportunity for facilitative and disruptive intertrial effects to occur. The authors show that benefits and costs associated with certain singletons depend at least partly on the preceding trial type. Results are in line with dimensional weighting and perceptual priming accounts, which propose a (semi-) automatic transfer of dimensional activity from one trial to the next. Results also indicate that priming is set independently for each dimension.

Visual search for a conjunction target is made easier when distractor items are temporally segregated over time to produce two separate old and new groups (the new group containing the target item). The benefit of presenting half the distractors first is known as the preview effect. Recently, some researchers have argued that the preview effect occurs because new stimuli capture attention. This account was tested in the present study by using a novel 'top-up' condition that exploits the fact that when previews appear only briefly before the search display, there is minimal preview benefit. We show that effects of a brief preview can be 'topped up' by an earlier exposure of the same items, even when the preview disappears between its first and second presentations. This top-up effect demonstrates that the history of the old stimuli is important for the preview benefit, contrary to the account favoring onset capture. We discuss alternative accounts of how the preview benefit arises.

Performance in a visual search task becomes more efficient if half of the distractors are presented before the rest of the stimuli. This 'preview benefit' may partly be due to inhibition of the old (previewed) items. The preview effect is abolished, however, if the old items offset briefly before reappearing (D. G. Watson & G. W. Humphreys, 1997). The authors examined whether this offset effect still occurred if the old items undergo occlusion. Results show that a preview benefit was found when the old items were occluded but not otherwise, consistent with the idea of top-down attentional inhibition being applied to the old items. The preview benefit is attenuated, however, by movement of the irrelevant stimuli in the displays.