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The current study uses an RT distribution analysis approach to examine the self-bias in face categorization. In two experiments we systematically manipulated the decision boundaries between the self, familiar, and unfamiliar others in face categorization tasks. For the first time in studies of self-categorization we estimated parameters from ex-Gaussian fits of reaction time distributions in order to capture the influence of different boundaries on the latency distribution of the categorization responses. The results showed that the distribution of responses to self faces was stable regardless of the face context and the task demands, and changes in context only shifted the response distribution in time. In contrast, varying the decisions with familiar and unfamiliar faces changed the shape of the RT distributions in addition to shifting RTs in time. The results indicate that, in contrast to our perception of familiar and unfamiliar faces of other people, self face perception forms a unique perceptual category unaffected by shifts in context and task demands. [ABSTRACT FROM PUBLISHER]

Assessing the implicit attitudes and beliefs of offenders has proved difficult over decades of work and research with offender samples. The purpose of this paper is to outline the research related to the use of the emotional Stroop task and to encourage researchers and practitioners to use it as a measure to assess the implicit attitudes of offenders within their assessments. We consider the factors that may influence Stroop results along with the research considerations that need to be taken into account when using an emotional Stroop paradigm. Currently, a significant limitation of the emotional Stroop task is a lack of standard word stimulus sets that are able to distinguish between offender types. This limitation could seriously impede further development of this tool. Suggestions for future research are proposed. [ABSTRACT FROM AUTHOR]

We investigated spatial and temporal deficits following brain injury using the temporal order judgement (TOJ) task. Patients judged the order in which two letters appeared to the left and right of fixation. We measured the extent of any spatial bias and the temporal resolution of the decision. Temporal and spatial deficits on the TOJ task were significantly correlated. The spatial bias on the TOJ task was also correlated with the spatial bias on a neglect task and with unilateral deficits on an extinction task, but not with extinction itself. These spatial deficits were all associated with damage to contralateral temporoparietal cortex. In contrast, the temporal resolution of TOJs was linked specifically to deficits in processing multiple stimuli on the neglect and extinction tasks and to damage to the right parietal lobe and the cerebellum. These data suggest that spatial and temporal deficits on the TOJ task reflect different underlying processes. [ABSTRACT FROM PUBLISHER]

When people search a display for a target defined by a unique feature, fast saccades are predominantly stimulus-driven whereas slower saccades are primarily goal-driven. Here we use this dissociative pattern to assess whether feature-based selection in patients with lateralized spatial attention deficits is impaired in stimulus-driven processing, goal-driven processing, or both. A group of patients suffering from extinction or neglect after parietal damage, and a group of healthy, age-matched controls, were instructed to make a saccade to a uniquely oriented target line which was presented simultaneously with a differently oriented distractor line. We systematically varied the salience of the target and distractor by changing the orientation of background elements, and used a time-based model to extract stimulus-driven (salience) and goal-driven (target set) components of selection. The results show that the patients exhibited reduced stimulus-driven processing only in the contralesional hemifield, while goal-driven processing was reduced across both hemifields. [ABSTRACT FROM PUBLISHER]

A single case study of a patient (FK) with utilization disorder following bilateral damage to medial frontal and anterior temporal cortices is reported. FK had to localize a search target following presentation of an earlier verbal or visual cue. Search was strongly affected by semantic/visual associations between the cue and search items. Although FK was unable to name the hue of an incongruent Stroop word, his attention was drawn to a color in the display matching the hue of the cue word. FK's ability to inhibit a response activated by the cueing of attention was impaired. There is dissociation between top-down attention cueing and response inhibition. [ABSTRACT FROM PUBLISHER]

We examined the effects of cue luminance on visual orienting. Experiment 1 established that the commonly-found early facilitation and late inhibition of return (IOR) effects were independent of cue luminance with single cues in terms of their amplitude, although IOR was delayed in the low compared to the high luminance cue condition. In contrast, Experiment 2 revealed that, with dual cues of mixed luminance, both facilitation and IOR effects were found only with bright cues. When cues had equal luminance, however, there were cueing effects for two cued locations but only when the cues were bright. The data were accommodated in a neural network model of biased competition in which cueing effects emerge at more than one location provided input activation is sufficient to overcome competitive damping of the selection system. [ABSTRACT FROM PUBLISHER]

We report data examining the relations between endogenous allocation of visual attention and effects of motor-preparation on attention. We tested a patient with a spatial bias in perceptual report following damage to the left inferior parietal lobe and superior temporal gyrus. Previously we have shown that the spatial bias in report can be reduced when a movement is planned to where a target falls in the contralesional field, while the bias is exacerbated when a movement is planned to the ipsilesional side (Kitadono & Humphreys, 2007, Cognitive Neuropsychology, 24). Here we pitted the effects of planning a movement to the contra- or ipsilesional side against the effects of endogenous visual attention, manipulated by varying the probability of where a target would fall. In a no-movement baseline, there was better identification of contralesional targets when there was a good likelihood of targets appearing on the contralesional side (the 20-80 and 50-50 conditions) compared with when targets had a low probability of occurring there (the 80-20 condition). This sensitivity to target probability interacted with the effects of planning a movement to the contra- or ipsilesional side. When the target had a good probability of falling in the contralesional field (the 20-80 and 50-50 conditions), planning a movement to the ipsilesional side disrupted contralesional report. When there was a high probability of an ipsilesional target (the 80-20 condition), planning a movement to a congruent side improved contralesional report. The results indicate that effects of endogenous attention and of motor-based attention influence a common system controlling visual orienting. [ABSTRACT FROM AUTHOR]

The attentional blink, a measure of the temporal dynamics of visual processing, has been documented to be more pronounced following brain lesions that are associated with visual neglect. This suggests that, in addition to their spatial bias in attention, neglect patients may have a prolonged dwell time for attention. Here the attentional dwell time was examined in patients with damage focused on either posterior parietal or frontal cortices. In three experiments, we show that there is an abnormally pronounced attentional dwell time, which does not differ in patients with posterior parietal and with frontal lobe lesions, and this is associated with a measure of selective attention but not with measures of spatial bias in selection. These data occurred both when we attempted to match patients and controls for overall differences in performance and when a single set stimulus exposure was used across participants. In Experiments 1 and 2, requiring report of colour–form conjunctions, there was evidence that the patients were also impaired at temporal binding, showing errors in feature combination across stimuli and in reporting in the correct temporal order. In Experiment 3, requiring only the report of features but introducing task switching led to similar results. The data suggest that damage to a frontoparietal network can compromise temporal selection of visual stimuli; however, this is not necessarily related to a deficit in hemispatial visual attention but it is to impaired target selection. We discuss the implications for understanding visual selection. [ABSTRACT FROM PUBLISHER]

Patients who have had a stroke resulting in the deficit of visuo-spatial neglect are normally not provided with a powered wheelchair, as they are either considered or found to be unsafe navigating about their environment. As these patients are relatively unlikely to regain functional mobility by walking, the denial of alternative forms of mobility is of particular concern. Modest progress has been made over the past two decades with regards to the rehabilitation of neglect but there have been calls for further research which addresses 'real world' measures of independence such as wheelchair navigation. In this study, we investigated the ability of patients with neglect to improve their performance when navigating a powered wheelchair by using theoretically-driven strategies that have shown promise in previous studies (spatial cueing and limb activation). Strategies were applied and tested in the most realistic and practical manner for each individual, based on their abilities and concurrent deficits. Performance was improved by the experimental strategies. The data suggest it is possible to apply theoretically-driven strategies to improve wheelchair navigation in patients with neglect and are supportive of further studies that could lead to improved access to powered mobility by this population in the future. [ABSTRACT FROM AUTHOR]

Participants held the size of a cue in working memory and looked for a target letter across local and global levels of hierarchical, compound letters. There was no effect of whether the cue size matched the size of the local or global letter, even when the size memory task was made difficult. The null effect of cue size was also found under priming conditions, when size had to be identified but not held in memory. Although cue size did not affect subsequent selection in these experiments, cue identity did. There were effects of size, however, on the magnitude of cueing effects, irrespective of whether targets were at the local or global level. The data are discussed in terms of the effects of overlap between the contents of WM and the attentional set for targets, and the role of focused and distributed attention on selection. Critically, the data run counter to the idea that local and global stimuli are selected by opening an 'attentional window' of a particular size in working memory and matching this to the target letter. [ABSTRACT FROM AUTHOR]

Two experiments examined extinction to stimuli presented either with contracting or expanding motion. Experiment 1 used solid shapes which either increased or decreased in size rapidly, consistent with looming motion. Experiment 2 employed random dots so that stimulus size was not confounded with type of motion. In both experiments extinction was modulated by the type of motion presented, with extinction most evident when a contracting object was in the weaker visual field. In addition, in Experiment 2 there was evidence for grouping modulating extinction, when there were looming stimuli in both fields. The results suggest that looming motion is a powerful determinant of stimulus salience in selective attention. [ABSTRACT FROM AUTHOR]

Patients with extinction show a characteristic impairment in the identification of objects when two items are presented simultaneously, typically reporting the ipsilesional item only. The effect is thought to be due to a spatial bias advantaging the ipsilesional item under conditions of competing concurrent stimulation. Action relations between objects can result in recovery from extinction as the object pair may be perceived as a single group rather than competing perceptual units. However, objects interacting together can also have implied motion. Here we test whether implied motion is necessary to generate recovery from extinction. We varied orthogonally whether animate and inanimate objects were paired together in positions related or unrelated to action. Implied motion was greater when an animate object was present than when both stimuli were inanimate. Despite this, recovery from extinction was greater when actions were shown between inanimate objects. We suggest that actions between inanimate objects are perceived more easily due to the surfaces of these stimuli being designed for functional goals (e.g., the flat surface of a hammer head is designed to hit the flattened head of a nail). Attention is sensitive to the fit between potential action and the functional properties of objects, and not just to implied motion between stimuli. [ABSTRACT FROM AUTHOR]

Using a cued conjunction search task, Anderson, Heinke, and Humphreys (2010) demonstrated larger effects from cueing target colour than from cueing target orientation. In this study, we separated the implicit (nonexpectation-dependent) and explicit (expectation-dependent) effects of orientation and colour visual cues. In Experiment 1, we replicated the original findings for short cue durations (100-200 ms), demonstrating that cues matching the physical property of the target on 80% of trials exert a rapid effect on search. These early cueing effects on reaction times were supported by evidence of guidance from cues on early eye movements. Experiment 2 introduced a feature to the cue that randomly matched the colour or orientation of the target. When cue orientation was predictive, there were strong implicit effects based on whether the colour of the cue and target matched. When cue colour was predictive, there were only weak effects from the cue's orientation. Implicit effects from cue colour remained when orientation-predictive cues were used and colour was unlikely to predict the target (Experiment 3). The data suggest that strong effects of colour cueing result from a combination of implicit and explicit processes, whereas effects from orientation cues are largely limited to the explicit guidance of visual search. [ABSTRACT FROM AUTHOR]

Patients with Balint's syndrome are known to make abnormal numbers of illusory conjunctions (ICs) when presented with multiple stimuli and asked to report the features of one. We used two converging procedures to assess the time course of these errors. In Experiments 1 and 2 the errors produced by a patient with Balint's syndrome, GK, were examined as a function of when he responded. We find that ICs were present even in GK's fastest responses, but that they also increased when GK responded slowly. In Experiment 3 we varied the exposure duration of the stimuli. With short stimulus exposures GK made ICs that he was certain were correct. With longer exposures there was an increase in the number of ICs where GK expressed uncertainty. In contrast to these “uncertain” ICs, feature errors decreased as the exposure duration increased. We propose that the ICs present in GK's fastest responses, and that arise with short stimulus exposures, reflect impairments at a first stage of binding. In addition to this, “uncertain” ICs arise on trials with slow responses, and with long exposures, due to performance then being affected by impairments to a second process dependent on bound features being consolidated into a more stable representation. The role of this consolidation process is limited when responses are made rapidly and exposure durations limited. This two-stage account is discussed in relation to other accounts of feature binding. [ABSTRACT FROM AUTHOR]

There is a long and ongoing debate about whether subitizing and counting are separable processes. In the present paper we report a single case, MH, who presents with a dissociation in subitizing and counting. MH was spared in his ability to enumerate small numbers accurately along with a marked inability to count larger numbers. We show that non-visual counting was intact and visual counting improved when a motor record of counting could be maintained. Moreover, when larger numbers of items were spatially grouped into 2 subitizable units, performance dramatically improved. However, color grouping did not aid MH's performance, despite his being sensitive to color segmentation. In addition, MH made more re-visits of inspected locations than controls, and he was less aware of a re-visitation being made. The data cannot be explained in terms of general working memory problems (verbal working memory was relatively spared), or general number comprehension problems (e.g., simple sums and counting of auditory items was intact); but they can parsimoniously be accounted for in terms of impaired visuo-spatial memory. The findings support the argument that at least some processes are specific to counting and are not required for subitization - in particular spatial coding and memory for previously inspected locations. [ABSTRACT FROM AUTHOR]

Insights into the functional nature and neuroanatomy of spatial attention have come from research in neglect patients but to date many conflicting results have been reported. The novelty of the current study is that we used voxel-wise analyses based on information from segmented grey and white matter tissue combined with diffusion tensor imaging to decompose neural substrates of different neglect symptoms. Allocentric neglect was associated with damage to posterior cortical regions (posterior superior temporal sulcus, angular, middle temporal and middle occipital gyri). In contrast, egocentric neglect was associated with more anterior cortical damage (middle frontal, postcentral, supramarginal, and superior temporal gyri) and damage within subcortical structures. Damage to intraparietal sulcus (IPS) and the temporo-parietal junction (TPJ) was associated with both forms of neglect. Importantly, we showed that both disorders were associated with white matter lesions suggesting damage within long association and projection pathways such as the superior longitudinal, superior fronto-occipital, inferior longitudinal, and inferior fronto-occipital fascicule, thalamic radiation, and corona radiata. We conclude that distinct cortical regions control attention (a) across space (using an egocentric frame of reference) and (b) within objects (using an allocentric frame of reference), while common cortical regions (TPJ, IPS) and common white matter pathways support interactions across the different cortical regions. [ABSTRACT FROM AUTHOR]

It has been argued that area hMT+/V5 in humans acts as a motion filter, enabling targets defined by a conjunction of motion and form to be efficiently selected. We present data indicating that (a) damage to parietal cortex leads to a selective problem in processing motion-form conjunctions, and (b) that the presence of a structurally and functional intact hMT+/V5 is not sufficient for efficient search for motion-form conjunctions. We suggest that, in addition to motion-processing areas (e.g., hMT+/V5), the posterior parietal cortex is necessary for efficient search with motion-form conjunctions, so that damage to either brain region may bring about deficits in search. We discuss the results in terms of the involvement of the posterior parietal cortex in the top-down guidance of search or in the binding of motion and form information. [ABSTRACT FROM AUTHOR]

What factors determine stimulus-driven responses in patients with utilization behaviour? We examined this question by assessing the influence of an irrelevant cue on visual search in a patient showing evidence of utilization behaviour (F.K.), following bilateral damage to the medial frontal and temporal lobes. Despite being able to repeat the instructions, F.K. often responded to an item in the search display that matched the cue rather than the target. This effect was reduced under certain conditions: (a) when the cue-search interval increased, (b) when F.K. paid less attention to the cue, and (c) when the target discrimination task was made more difficult. On the other hand, the effect arose even when the cue was always invalid. We suggest that information from the cue competed with the top-down set to determine search. F.K.'s lesion makes it difficult for him to impose top-down knowledge rapidly, leading to responses automatically being based on attended, but irrelevant, cues under short cue-display intervals. [ABSTRACT FROM AUTHOR]

The search over time and space (sSoTS) model attempts to simulate both the spatial and the temporal aspects of human visual search using spiking level neurons, which incorporate some biologically plausible aspects of neuronal firing. The model contains pools of units that (a) code basic features of objects, presumed to reside in the ventral visual stream, and (b) respond in a feature-independent way to stimulation at their location, presumed to operate in the posterior parietal cortex. We examined the effects of selective lesioning neurons responding to one side of the location map. Unilateral damage introduced spatial biases into selection that affected conjunction more than single-feature search. In addition, there was an impaired ability to segment stimuli over time as well as space (e.g., in preview search). These results match previously reported data on patients with posterior parietal lesions. In addition we show that spatial biases in selection increase under conditions in which there is decreased activity from excitatory neurotransmitters, mimicking effects of reduced arousal. Further simulations explored the effects of time and of visual grouping on extinction, generating predictions that were then tested empirically. The model provides a framework for linking behavioural data from patients with neural-level determinants of visual attention. [ABSTRACT FROM AUTHOR]

In the present paper we show that, in patients with poor semantic representations, the naming of real objects can improve when naming takes place after patients have been asked to use the objects, compared with when they name the objects either from vision or from touch alone, or together. In addition, the patients were strongly affected by action when required to name objects that were used correctly or incorrectly by the examiner. The data suggest that actions can be cued directly from sensory-motor associations, and that patients can then name on the basis of the evoked action. [ABSTRACT FROM AUTHOR]

Prader-Willi syndrome (PWS) and Fragile X syndrome (FraX) are associated with distinctive cognitive and behavioural profiles. We examined whether repetitive behaviours in the two syndromes were associated with deficits in specific executive functions. PWS, FraX, and typically developing (TD) children were assessed for executive functioning using the Test of Everyday Attention for Children and an adapted Simon spatial interference task. Relative to the TD children, children with PWS and FraX showed greater costs of attention switching on the Simon task, but after controlling for intellectual ability, these switching deficits were only significant in the PWS group. Children with PWS and FraX also showed significantly increased preference for routine and differing profiles of other specific types of repetitive behaviours. A measure of switch cost from the Simon task was positively correlated to scores on preference for routine questionnaire items and was strongly associated with scores on other items relating to a preference for predictability. It is proposed that a deficit in attention switching is a component of the endophenotypes of both PWS and FraX and is associated with specific behaviours. This proposal is discussed in the context of neurocognitive pathways between genes and behaviour. [ABSTRACT FROM AUTHOR]

We report data on illusory conjunctions (ICs) in a colour/letter identification task from a patient with simultanagnosia following bilateral parietal lesions and from a study using transcranial magnetic stimulation (TMS) with normal participants. We show that, even though target conjunctions were reported well above chance across a range of exposure durations, ICs were only generated at longer display exposures while feature errors decreased across time. With normal participants we found that TMS to the right posterior parietal cortex but not to occipital cortex increased the number of ICs. Moreover, ICs tended to occur after delayed stimulation, with the critical time window for stimulation being later for ICs than for feature errors. The data provide support for the critical role of posterior parietal cortex in a late process of feature binding. [ABSTRACT FROM AUTHOR]

In order to explore parietal patients' difficulties in the processing of orientation information, we asked parietal patients (N = 8) and healthy and brain-damaged controls to imitate multicomponent actions where object orientation was one component. In Experiment 1 orientation was not the most relevant aspect of the action to be imitated, and the parietal group showed significant difficulties in processing object orientation. However, in Experiment 2, where orientation was placed at the top end of the goal hierarchy, the parietal group were able to process stimulus orientation sufficiently to place it within the goal hierarchy of the action and to reproduce it accurately. We conclude that patients with parietal lesions might be able to include object orientation in a goal hierarchy, but if their processing of orientation information is impaired they might be disproportionately prone to errors when object orientation is lower in the goal hierarchy and so not prioritized for processing resources. [ABSTRACT FROM AUTHOR]

Background: Remediation techniques for dysgraphia have focused on targeting different components of the theoretical models for spelling. Studies have revealed that targeting lexically oriented strategies can prove beneficial for patients with deep dysgraphia. Studies on short-term memory have also demonstrated a role of semantic knowledge in short-term retention Aims: Two variants of lexically oriented strategies were applied to remediate a deep dysgraphic patient, PH, and the role of imagery in supporting the learning was examined. Methods & Procedures: Retraining was explored using a visual-kinaesthetic learning technique, contrasting performance with high- and low-imagery words. Outcomes & Results: Positive effects of learning were demonstrated. There was effective initial learning of blocks of both high-imagery and low-imagery target words, but high-imagery words had a clear advantage in terms of longer-term maintenance. Conclusions: The data demonstrate that semantic knowledge may play a role in strengthening graphemic representations of words, helping in the maintenance of the orthography of target words over time. [ABSTRACT FROM AUTHOR]

For the first time, we report a spatial bias in visual short-term memory (VSTM) after left medial and inferior occipito-temporal damage. Our patient D.M. showed a spatial bias in report from VSTM, being more accurate at reporting stimuli presented in her left than her right visual field (Experiment 1). This spatial bias could not be attributed to a visual field deficit (Experiment 2) and was based on the relative rather than the absolute locations of the stimuli (Experiment 3). It was reduced when the transfer of items to VSTM was facilitated—for example, by grouping stimuli (Experiment 4) or by reducing the number of items to be remembered (Experiment 5). The spatial bias was attenuated when items moved from right to centre or left to centre, and D.M. was cued to report the item that would have been on the right or left, had the movement continued (Experiment 6). We conclude that posterior ventral damage can impair both the consolidation of new information in VSTM and the explicit report of consolidated information from VSTM. [ABSTRACT FROM AUTHOR]

Spatial information processing with respect to an egocentric reference frame has been shown to recruit a fronto-parietal network along the dorsal stream. The present study investigates how brain lesions in the relevant areas affect the ability to navigate through computer-simulated tunnels shown from a first person perspective. Our results suggest that parietal, but not frontal, patients are impaired in this task. They confused the direction of tunnel turns more frequently and made less accurate judgments about the location of the end position. Errors in map drawing suggest that the impairment may be linked to deficits in updating cognitive heading in the absence of corresponding perceptual information from the virtual environment. [ABSTRACT FROM AUTHOR]

The performance of two patients with visual agnosia was compared across a number of tests examining visual processing. The patients were distinguished by having dorsal and medial ventral extrastriate lesions. While inanimate objects were disadvantaged for the patient with a dorsal extrastriate lesion, animate items are disadvantaged for the patient with the medial ventral extrastriate lesion. The patients also showed contrasting patterns of performance on the Navon Test: The patient with a dorsal extrastriate lesion demonstrated a local bias while the patient with a medial ventral extrastriate lesion had a global bias. We propose that the dorsal and medial ventral visual pathways may be characterized at an extrastriate level by differences in local relative to more global visual processing and that this can link to visually based category-specific deficits in processing. [ABSTRACT FROM AUTHOR]

The ability to recognize individual faces is of crucial social importance for humans and evolutionarily necessary for survival. Consequently, faces may be "special" stimuli, for which we have developed unique modular perceptual and recognition processes. Some of the strongest evidence for face processing being modular comes from cases of prosopagnosia, where patients are unable to recognize faces whilst retaining the ability to recognize other objects. Here we present the case of an acquired prosopagnosic whose poor recognition was linked to a perceptual impairment in face processing. Despite this, she had intact object recognition, even at a subordinate level. She also showed a normal ability to learn and to generalize learning of nonfacial exemplars differing in the nature and arrangement of their parts, along with impaired learning and generalization of facial exemplars. The case provides evidence for modular perceptual processes for faces. [ABSTRACT FROM AUTHOR]

We report a series of 7 experiments examining the interaction between visual perception and action programming, contrasting 2 neuropsychological cases: a case of visual extinction and a case with extinction and optic ataxia. The patients had to make pointing responses to left and right locations, whilst identifying briefly presented shapes. Different patterns of performance emerged with the two cases. The patient with "pure" extinction (i.e., extinction without optic ataxia) showed dramatic effects of action programming on perceptual report. Programming an action to the ipsilesional side increased extinction (on 2-item trials) and tended to induce neglect (on 1-item trials); this was ameliorated when the action was programmed to the contralesional side. Separable effects of using the contralesional hand and pointing to the contralesional side were apparent. In contrast, the optic ataxic patient showed few effects of congruency between the visual stimulus and the action, but extinction when an action was programmed. This effect was particularly marked when actions had to be made to peripheral locations, suggesting that it reflected reduced resources to stimuli. These effects all occurred using stimulus exposures that were completed well before actions were effected. The data demonstrate interactions between action programming and visual perception. Programming an action to the affected side with the contralesional limb reduces "pure" extinction because attention is coupled to the end point of the action. However, in a patient with deficient visuo-motor coupling (optic ataxia), programming an action can increase a spatial deficit by recruiting resources away from perceptual processing. The implications for models of perception and action are discussed. [ABSTRACT FROM AUTHOR]

We provide evidence for long-term priming based on view-specific representations of neglected stimuli. A patient with visual neglect, M.P., was asked to search for a target presented amongst other objects on a table. Subsequently recognition memory was tested for items that were identified and for items missed in search. Items that were missed were rejected more slowly than novel items in the recognition memory task, providing evidence for implicit processing (Experiment 1). Implicit memory for missed items was both item-specific (Experiment 2) and view-specific (Experiment 3), and it was eliminated when there were intervening activities lasting about 1 hour (Experiment 4). There was also an implicit memory for distractors in the search task, which was item- but not view-specific (Experiments 2 and 3) and it lasted for at least an hour, even with other intervening activities (Experiment 4). The data suggest that the representations of neglected stimuli may differ qualitatively from those of nonneglected items, with representations of neglected objects being both view-specific and vulnerable across extended retention intervals. The results support the argument that attention is needed in order to encode object representations that are robust to view transformations and temporal decay or interference. [ABSTRACT FROM AUTHOR]

The 'rubber hand' illusion was induced in a patient showing unilateral visual neglect, with the patient experiencing a shift in the felt position of his right hand towards a contralesional rubber hand. Immediately following the illusion, there were short-lasting reductions in neglect for bisecting about the midline and for cancelling multiple stimuli. No effects were found on the ability to encode briefly presented visual stimuli on the contralesional side. The data demonstrate that the illusion can temporarily alter some aspects of neglect, without altering basic visual encoding. The underlying mechanisms, and the relations to other rehabilitation procedures, are discussed. [ABSTRACT FROM AUTHOR]

We examined the role of the fronto-parietal cortex in top-down modulation of perceptual grouping by proximity, collinearity, and similarity, by recording event related brain potentials from two patients with fronto-parietal lesions and eight controls. We found that grouping by proximity and collinearity in the controls was indexed by short-latency activities over the medial occipital cortex and long-latency activities over the occipito-parietal areas. For the patients, however, both the short- and long-latency activities were eliminated or weakened. The results suggest that the fronto-parietal network is involved in facilitation of both the early and late grouping processes in the human brain. [ABSTRACT FROM AUTHOR]

In neuropsychological research, it is frequently necessary to compare the performance of a single case with that of a control sample. Recently, there has been a discussion about whether existing methods are adequate in preventing Type 1 errors due to increased variability in the single-case data (Crawford, Garthwaite, Howell, & Gray, 2004; Mitchell, Mycroft, & Kay, 2004; Mycroft, Mitchell, & Kay, 2002) and about the power of any comparisons. In this paper, we propose an extension of the modified t test introduced by Crawford and Howell (1998). We provide Monte Carlo simulations that show that it is possible to increase the power of the modified t test by retesting the single case. We also make available a computer program that implements the method introduced in this paper and that can be used by neuropsychologists to test for a difference between a single case and a control group. We apply our procedure to an example of a patient examined on the "Pyramids and Palm Trees" test. [ABSTRACT FROM AUTHOR]

We assessed the factors contributing to local capture in G.K., a patient with Balint's syndrome. G.K. found it difficult to identify the global shape of a compound stimulus, and his poor identification of the global shape was not resolved by introducing familiar local stimuli that were either from the same category as the global target but not tied to a response (Experiment 1) or that belonged to a different category to the target (Experiment 2). Effects of item familiarity were tested by examining local capture from Hebrew letters on compound English letters. Prior to training with the Hebrew letters, G.K. was able to identify the global compounds (Experiment 3a). In contrast, after training with the letters, there was a significant increase in local capture (Experiment 3b). Two additional experiments examined effects of local grouping. Local capture was reduced when the local elements were rectangles or ellipses and grouped by closure of local elements (Experiment 4). Global discrimination also improved when local items were unfamiliar rectangular figure eights (Experiment 5a). However, these grouping effects were counteracted by effects of familiarity when the local elements were changed slightly to become familiar number eights (Experiment 5b). The data suggest that familiar local items are likely to capture spatial attention, whilst grouping by closure between local elements can help global shapes compete for spatial attention with local elements in such patients. The impairment in global perception in Balint's syndrome is not all-or-none but graded according to the factors influencing local capture. [ABSTRACT FROM AUTHOR]

Stankiewicz, Hummel, and Cooper (1998) proposed that detailed coding of part–whole relations for objects is contingent on objects being attended. We report a neuropsychological test of this assertion. We examined the effects of left–right reflection on object matching in a group of patients with parietal damage and impaired attention to the contralesional side of space (Experiment 1). The patients were poor at matching objects subject to left–right reflection, relative to identical stimuli (Experiment 2). This was not due to a lack of sensitivity to information on the contralesional side. In a subsequent study, the patients were better at matching identical whole objects at fixation than when they just received half the object in their ipsilesional field (Experiment 3). However, unlike both nonlesioned controls and control patients with frontal lesions, the parietal patients were unaffected by altering the relative spatial locations of object features in their contralesional field (Experiment 4). The basic result, of poor performance with left–right-reflected items, was also replicated using a priming rather than an explicit matching procedure (Experiment 5). These results provide confirmation that visual attention, mediated by the posterior parietal cortex, is important for generating part–whole codes that facilitate the matching of mirror-reflected objects. [ABSTRACT FROM AUTHOR]

The study of the performance of patients with neurological disorders has been fruitful in revealing the nature and neural basis of inhibition of return (IOR). Thus, in recent years, studies have reported abnormal IOR in patients with Alzheimer's disease, patients diagnosed with schizophrenia, and brain-damaged patients. In the present study, we investigated the hypothesis that a spatial “disengagement deficit” (DD; Posner, Walker, Friedrich, & Rafal, 1984) contributed to the pattern of impaired IOR in the ipsilesional field of parietal patients, found in a previous work (Vivas, Humphreys, & Fuentes, 2003). In a first experiment, we replicated the attenuation of IOR for ipsilesional targets on those trials with a lateralized IOR procedure. With stimuli vertically aligned about fixation, we found intact IOR for both up and down targets. Most important, when we ameliorated the potential impact of a spatial DD by presenting both cues and target in the same hemifield, still we found impaired IOR in the ipsilesional field. We interpret these findings in terms of unilateral parietal damage leading to an imbalance of the relative salience of signals represented in a spatial map for directing attention. [ABSTRACT FROM AUTHOR]

We present a revised version of the Selective Attention for Identification Model (SAIM), using an initial feature detection process to code edge orientations. We show that the revised SAIM can simulate both efficient and inefficient human search, that it shows search asymmetries, and that top-down expectancies for targets play a major role in the model's selection. Predictions of the model for top-down effects are tested with human participants, and important similarities and dissimilarities are discussed. [ABSTRACT FROM AUTHOR]

A series of experiments are reviewed providing evidence for the idea that when new visual objects are prioritized, old objects are inhibited by a top-down controlled suppression mechanism—a process referred to as visual marking. Evidence for the top-down aspect of visual marking is presented, by showing that new object prioritization, as measured in the preview paradigm, depends on task settings and available attentional resources. Evidence for the inhibitory aspect is presented, by showing that selection of new items is impaired when these items share features with the old items. Such negative carryover effects occur within as well as between trials. Alternative accounts and the evidence for them is discussed. It is concluded that the various accounts are not mutually exclusive and that the data is best explained by a combination of mechanisms. [ABSTRACT FROM AUTHOR]

Deficits in task switching can be found after frontal lobe damage. Here we demonstrate an impairment in task switching specifically linked to when perceptual weights have to be moved between different dimensions of the same stimulus. A patient (DS) with left frontal lobe damage showed normal performance when he responded to the meaning (a word task) or location (a location task) of a word presented to the left or right of fixation when there was no switching between the tasks. However, when the two tasks were switched every 16 trials in a block, DS showed severe difficulty in performing both tasks (Experiment 1). There were then abnormally large switch costs and effects of stimulus–response congruency. The difficulty was not simply due to switching tasks per se: There were no costs of switching when one of the tasks was modified to have different stimulus displays from the other (Experiment 2). The deficit was also not greater when the switch had to be made from a well-practised task to an unpractised task with more arbitrary stimulus–response mappings, indicating no particular problem in disengaging from a learned task or in configuring new stimulus–response links (Experiment 4). We suggest instead that DS was impaired at shifting attentional weights across different dimensions of the same stimulus, a process required with practised and unpractised tasks alike. The results link this process of shifting attention across stimulus dimensions to the left frontal lobe. [ABSTRACT FROM AUTHOR]

We investigated the effects of long-term training using prism adaptation on a patient with chronic neglect. A positive effect of prism adaptation was apparent on tests of visuo-spatial processing (cancellation, bisection, and grasping), but there was no benefit for neglect on the detection of errors on the contralesional side of words or on the detection the left side of chimeric faces. Across training sessions, the benefit of adaptation on immediate performance decreased, but it increased across sessions and within sessions when performance was tested up to 90 minutes after adaptation. The beneficial effect was maintained up to 1 year posttraining. In later sessions there were also increased negative after-effects following prism adaptation, as training progressed. There was no improvement on tests of mathematical cognition, which comprised an independent deficit in this patient. The data suggest that prolonged prism training can induce long-term adaptive spatial realignment of visuo-motor mappings, ameliorating some aspects of neglect. We discuss the implications for the rehabilitation of neglect and for understanding the neglect syndrome more generally. [ABSTRACT FROM AUTHOR]

An inefficient visual search task can be facilitated if half the distractor items are presented as a preview prior to the presentation of the remaining distractor items and target. This benefit in search is termed the preview effect . Recent research has found that a preview effect can still occur if the previewed items disappear before reappearing again just before the search items (the “top-up” procedure). In this paper we investigate the attentional demands of processing during the preview and the top-up periods. Experiment 1 found that if attention is withdrawn from the top-up stage then no preview effect occurs. Likewise if attention is withdrawn from the initial preview period then the preview effect is reduced (Experiment 2). The data suggest that the preview effect is dependent on attention being paid both to the initial display and also to the re-presentation of the old display before the search display appears. The data counter accounts of preview search in terms of automatic attention capture by new items or by inhibition of return. We discuss alternative accounts of the results, and in particular suggest an amalgamation of a temporal grouping and a visual marking account of preview search. [ABSTRACT FROM AUTHOR]

We report a case-study of YE, a 54-year-old person who suffered multiple shell injuries that caused a right-parietal lesion and left hemianopia, almost 30 years ago. We conducted 4 experiments using a basic extinction paradigm in which YE had to report single stimuli presented on the left or right or two stimuli presented simultaneously in both visual fields. We show that extinction was selectively affected both by increasing the relative perceptual salience of the contralesional stimulus and by cueing attention to the contralesional side. The effects of perceptual salience and attentional cueing interacted, with cueing being more effective when the stimuli had relatively high perceptual salience. The data are consistent with attentional and perceptual factors interacting to determine the competition between left and right side stimuli that underlies extinction. [ABSTRACT FROM AUTHOR]