Search

In this review, we discuss how neuropsychological impairments in visual selection can inform us about how selection normally operates. Using neuroanatomical and behavioral evidence on the disorders of neglect, extinction, and simultanagnosia, we propose functional and anatomical links between different aspects of visual selection and distinct sites in the posterior parietal cortex (PPC). This includes linking: (i) bottom-up attentional capture and the right temporo-parietal junction (TPJ); (ii) top-down segmentation of displays and the medial PPC; (iii) grouping, individuation and identification, and the inferior intra-parietal sulcus (IPS) bilaterally; and (iv) the suppression of saliency and the left IPS. In addition, when neuropsychological studies are combined with fMRI, there is evidence that these regions of the PPC interact with striate and extra-striate cortical areas, which respond to specific properties of stimuli. Selection should be viewed as an emergent property of a network of areas involving both ventral and dorsal cortex.

The ability to represent desires and intentions as two distinct mental states was investigated in patients with parietal (N = 8) and frontal (N = 6) lesions and in age-matched controls (N = 7). A task was used where the satisfaction of the desire and the fulfilment of the intention did not co-vary and were manipulated in a 2 x 2 set. In two experiments we show that lesions to the frontal lobe may impair the ability to deal with desires when their outcome is not congruent with that of the intention, and that parietal damage--especially if it encompasses the left temporo-parietal junction--may cause severe difficulties in the processing of both desires and intentions. The implications of the results for the neuropsychological and the developmental literature are discussed. (Contains 3 tables and 4 figures.)

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.

Multiple accounts have been proposed to explain category-specific recognition impairments. Some suggest that category-specific deficits may be caused by a deficit in recurrent processing between the levels of a hierarchically organized visual object recognition system. Here, we tested predictions of interactive processing theories on the emergence of category-selective naming deficits in neurologically intact observers and in patient GA, a single case showing a category-specific impairment for natural objects after a herpes simplex encephalitis infection. Fragmented object outlines were repeatedly presented until correct naming occurred (maximum 10 times), and the fragments increased in length with every repetition. We studied how shape complexity, object category, and fragment curvature influence the timing of correct object identification. The results of a survival analysis are consistent with the idea that deficits in recurrent processing between low- and high-level visual object representations can cause category-selective impairments. [ABSTRACT FROM AUTHOR]

The Treisman Bartlett lecture, reported in theQuarterly Journal of Experimental Psychologyin 1988, provided a major overview of the feature integration theory of attention. This has continued to be a dominant account of human visual attention to this day. The current paper provides a summary of the work reported in the lecture and an update on critical aspects of the theory as applied to visual object perception. The paper highlights the emergence of findings that pose significant challenges to the theory and which suggest that revisions are required that allow for (a) several rather than a single form of feature integration, (b) some forms of feature integration to operate preattentively, (c) stored knowledge about single objects and interactions between objects to modulate perceptual integration, (d) the application of feature-based inhibition to object files where visual features are specified, which generates feature-based spreading suppression and scene segmentation, and (e) a role for attention infeature confirmationrather thanfeature integrationin visual selection. Afeature confirmationaccount of attention in object perception is outlined. [ABSTRACT FROM PUBLISHER]

The ability to search efficiently for visual targets among distractors can break down after a variety of brain lesions, but the specific processes affected by the lesions are unclear. We examined search over space (conjunction search) and over time plus space (preview search) in a consecutive series of patients with acquired brain lesions. We also assessed performance on standard neuropsychological measures of visuospatial short-term memory (Corsi Block), sustained attention and memory updating (the contrast between forward and backward digit span), and visual neglect. Voxel-based morphometry analyses revealed regions in the occipital (middle occipital gyrus), posterior parietal (angular gyrus), and temporal cortices (superior and middle temporal gyri extending to the insula), along with underlying white matter pathways, associated with poor search. Going beyond standard voxel-based morphometry analyses, we then report correlation measures of structural damage in these regions and the independent neuropsychological measures of other cognitive functions. We find distinct patterns of correlation in areas linked to poor search, suggesting that the areas play functionally different roles in search. We conclude that neuropsychological disorders of search can be linked to necessary and distinct cognitive functions, according to the site of lesion. [ABSTRACT FROM AUTHOR]

The current research examined the influence of ingroup/outgroup categorization on brain event-related potentials measured during perceptual processing of own- and other-race faces. White participants performed a sequential matching task with upright and inverted faces belonging either to their own race (White) or to another race (Black) and affiliated with either their own university or another university by a preceding visual prime. Results demonstrated that the right-lateralized N170 component evoked by test faces was modulated by race and by social category: the N170 to own-race faces showed a larger inversion effect (i.e., latency delay for inverted faces) when the faces were categorized as other-university rather than own-university members; the N170 to other-race faces showed no modulation of its inversion effect by university affiliation. These results suggest that neural correlates of structural face encoding (as evidenced by the N170 inversion effects) can be modulated by both visual (racial) and nonvisual (social) ingroup/outgroup status. [ABSTRACT FROM PUBLISHER]

Hierarchical models of visual processing assume that global pattern recognition is contingent on the progressive integration of local elements across larger spatial regions, operating from early through intermediate to higher-level cortical regions. Here, we present results from neuropsychological fMRI that refute such models. We report two patients, one with lesions to intermediate ventral regions and the other with damage around the intraparietal sulcus (IPS). The patient with ventral damage showed normal behavioral and BOLD responses to global Glass patterns. The patient with IPS damage was impaired in discriminating global patterns and showed a lack of significant responses to these patterns in intermediate visual regions spared by the lesion. However, this patient did show BOLD activity to translational patterns, where local element relations are important. These results suggest that activation of intermediate ventral regions is not necessary to code global patterns; instead global patterns are coded in a heterarchical fashion. High-level regions of dorsal cortex are necessary to generate global pattern coding in intermediate ventral regions; in contrast, local integration processes are not sufficient. [ABSTRACT FROM AUTHOR]

Patients with Balint's syndrome are typically impaired at perceiving multiple objects simultaneously, and at evaluating the relationship between multiple objects in a scene (simultanagnosia). These deficits may not only be observed in complex scenes, but also when local elements of individual objects must be integrated into a perceptual global whole. Thus, unlike normal observers, patients with simultanagnosia typically show a bias towards the local forms, even to the extent that they cannot identify the global stimuli. However, we have previously shown that global processing is still attainable in Balint patients in certain scenarios (e.g., when local elements are unfamiliar). This suggests that in addition to a possible perceptual deficit that favors the local elements in these patients, impaired attentional control may be at the core of their unique performance. To test this hypothesis we manipulated the perceptual saliency of the local and global elements in a compound letter task so that it included global-more-salient or local-more-salient displays. We show that a Balint patient was able to accurately identify both global and local targets as long as they were the salient aspect of the compound letter. However, substantial impairment was evident when either the global or local elements were the less salient aspect of the compound letter. We conclude that in Balint's syndrome there is a failure of flexible top-down attention both in biasing attention away from salient irrelevant aspects of the display (salience-based-selection) and in impaired disengagement from irrelevant but salient items once they have been selected. [ABSTRACT FROM AUTHOR]

We review neuropsychological evidence for visual selection operating in different reference frames. There is general agreement that there may be a separation of coding space near to and farther from the body, and that deficits in selecting stimuli within each form of spatial representation may be impaired in patients with unilateral neglect. However, there remains a lack of consensus about whether all forms of spatial representation relate to the body or whether there are spatial representations based on reference frames abstracted from the body (allocentric and object-centered spatial codes). Here we will review the evidence for spatial coding in these more abstracted reference frames (allocentric and object-centered but also environmental) and argue for the psychological reality of (at least) allocentric spatial coding. We discuss computational accounts of how such codes may be created as objects are selected. [ABSTRACT FROM AUTHOR]

Abstract: Previous studies show that positioning familiar pairs of objects for action ameliorates visual extinction in neuropsychological patients (Riddoch, Humphreys, Edwards, Baker, & Willson, 2003). This effect is stronger when objects are viewed from a self-perspective and are placed in locations congruent with the patient''s premorbid handedness (Humphreys, Wulff, Yoon, & Riddoch, 2010a), consistent with it being modulated by a motor response to the stimuli. There is also some evidence that extinction can be reduced with unfamiliar object pairs positioned for action (Riddoch et al. 2006), but the effects of reference frame and hand-object congruence have not been examined with such items. This was investigated in the present experiment. There was greater recovery from extinction when objects were action-related compared to when they were not, in line with previous studies. In addition, patients benefited more when they saw action-related pairs from a third-person than from a first-person perspective. Interestingly, on trials where extinction occurred, there was a bias reporting the ‘active’ object on the extinguished side—a reversal of the standard pattern of extinction—but only when objects were seen from a self-perspective. The data show that several factors contribute to the effects of action relations on attention, depending upon the familiarity of the object pairs and the reference frame that stimuli have been seenin. [Copyright &y& Elsevier]

This study is the first to assess lesion-symptom relations for subitizing and counting impairments in a large sample of neuropsychological patients (41 patients) using an observer-independent voxel-based approach. We tested for differential effects of enumerating small versus large numbers of items while controlling for hemianopia and visual attention deficits. Overall impairments in the enumeration of any numbers (small or large) were associated with an extended network, including bilateral occipital and fronto-parietal regions. Within this network, severe impairments in accuracy when enumerating small sets of items (in the subitizing range) were associated with damage to the left posterior occipital cortex, bilateral lateral occipital and right superior frontal cortices. Lesions to the right calcarine extending to the precuneus led to patients serially counting even small numbers of items (indicated by a steep response slope), again demonstrating an impaired subitizing ability. In contrast, impairments in counting large numerosities were associated with damage to the left intraparietal sulcus. The data support the argument for some distinctive processes and neural areas necessary to support subitization and counting with subitizing relying on processes of posterior occipital cortex and with counting associated with processing in the parietal cortex. [ABSTRACT FROM AUTHOR]

Because of our limited processing capacity, different elements of the visual scene compete for the allocation of processing resources. One of the most striking deficits in visual selection is simultanagnosia, a rare neuropsychological condition characterized by impaired spatial awareness of more than one object at time. To decompose the neuroanatomical substrates of the syndrome and to gain insights into the structural and functional organization of visuospatial attention, we performed a systematic evaluation of lesion patterns in a group of simultanagnosic patients compared with patients with either (i) unilateral visuospatial deficits (neglect and/or extinction) or (ii) bilateral posterior lesions without visuospatial deficits, using overlap/subtraction analyses, estimation of lesion volume, and a lesion laterality index. We next used voxel-based morphometry to assess the link between different visuospatial deficits and gray matter and white matter (WM) damage. Lesion overlap/subtraction analyses, lesion laterality index, and voxel-based morphometry measures converged to indicate that bilateral parieto-occipital WM disconnections are both distinctive and necessary to create symptoms associated with simultanagnosia. We also found that bilateral gray matter damage within the middle frontal area (BA 46), cuneus, calacarine, and parieto-occipital fissure as well as right hemisphere parietal lesions within intraparietal and postcentral gyri were associated with simultanagnosia. Further analysis of the WM based on tractography revealed associations with bilateral damage to major pathways within the visuospatial attention network, including the superior longitudinal fasciculus, the inferior fronto-occipital fasciculus, and the inferior longitudinal fasciculus. We conclude that damage to the parieto-occipital regions and the intraparietal sulcus, together, with bilateral WM disconnections within the visuosptial attention network, contribute to poor visual processing of multiple objects and the loss of processing speed characteristic of simultanagnosia. [ABSTRACT FROM AUTHOR]

Summary: The human occipito-temporal cortex is preferentially activated by images of objects as opposed to scrambled images . Touching objects (versus textures) also activates this region . We used neuropsychological fMRI to probe whether dorsal regions of the lateral occipital cortex (LO) are activated in tactile recognition without mediation through visual recognition. We tested a patient (HJA) with visual agnosia due to bilateral lesions of the ventral occipito-temporal cortex but spared dorsal LO. HJA''s recognition of visual objects was impaired . Nevertheless, his tactile recognition was preserved. We measured brain activity while participants viewed and touched objects and textures. There was overlapping activity in regions including LO and cerebellum for both stimuli for control participants, including new regions not before considered bimodal. For HJA, there were overlapping regions in the intact dorsal LO. Within a subset of the regions found in control participants, HJA showed activity only for tactile objects, suggesting that these regions are specifically involved in successful multimodal recognition. Activation of dorsal LO by tactile input is not secondary to visual recognition but can operate directly through tactile input. [Copyright &y& Elsevier]

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. [ABSTRACT FROM AUTHOR]

Abstract: Interactions between perception and action were examined by assessing the effects of action programming on extinction and neglect. In an extension of prior work, effects of sequential motor programming were assessed under conditions in which attention was first directed to an ipsilesional stimulus. Despite pointing and reporting a stimulus on the ipsilesional side first, programming a second action to the contralesional side reduced the spatial deficit on report, improving the report of contralesional stimuli (relative to when the patient just pointed to the ipsilesional side) while decreasing the report of ipsilesional items. The data suggest that perception and action interact through motor feedback to early visual coding, helping a patient overcome a lack of visual awareness to contralesional stimuli. This is effective even when attention has to be disengaged from the ipsilesional side suggesting that motor programming decreases ipsilesional capture and exerts a sustained influence on perception. [Copyright &y& Elsevier]

Abstract: We report data on the processing of facial emotion in a prosopagnosic patient (H.J.A.). H.J.A. was relatively accurate at discriminating happy from angry upright faces, but he performed at chance when the faces were inverted. Furthermore, with upright faces there was no configural interference effect on emotion judgements, when face parts expressing different emotions were aligned to express a new emergent emotion. We propose that H.J.A.''s emotion judgements relied on local rather than on configural information, and this local information was disrupted by inversion. A compensatory strategy, based on processing local face parts, can be sufficient to process at least some facial emotions. [Copyright &y& Elsevier]

We report data on the rehabilitation of action disorganisation syndrome (ADS). Although prior attempts to rehabilitate everyday actions in our patient, FK, had proved unsuccessful, we report positive results from using a verbalisation strategy. FK was taught a poem based on the steps involved in making a cup of tea. Following training, the everyday action was performed more successfully than prior to training, with the order of the actions in particular being improved when the poem was applied. In addition, there was evidence of error monitoring being carried out contingent on the verbalisation strategy. Across training sessions FK also became more likely to apply the poem and to perform the actions without prompting. However, there was relatively weak training effects across sessions, and the beneficial effects did not transfer to new tasks or to the same task with a different key object. The utility of the approach for severe cases of ADS is discussed. [ABSTRACT FROM AUTHOR]

We report data on patient FK, who presented with a marked deficit in accessing semantic knowledge about objects when tested across a range of input and output modalities. FK also showed a high degree of item-specific consistency in object identification, over and above effects due to object familiarity. We show that, despite being better at naming some objects than others, FK was equally poor at discriminating the superordinate categories of the stimuli. Also, he tended to be better at matching nameable items to a base-level label than to a superordinate-level label. We discuss the implications of the data for models of semantic memory. [ABSTRACT FROM AUTHOR]

We present neuropsychological evidence indicating that action influences spatial perception. First, we review evidence indicating that actions using a tool can modulate unilateral visual neglect and extinction, where patients are unaware of stimuli presented on one side of space. We show that, at least for some patients, modulation comes about through a combination of visual and motor cueing of attention to the affected side (Experiment 1). Subsequently, we review evidence that action-relations between stimuli reduce visual extinction; there is less extinction when stimuli fall in the correct colocations for action relative to when they fall in the incorrect relations for action and relative to when stimuli are just associatively related. Finally, we demonstrate that action relations between stimuli can also influence the binding of objects to space, in a patient with Balint's syndrome (Experiment 2). These neuropsychological data indicate that perception-action couplings can be crucial to our conscious representation of space. [ABSTRACT FROM AUTHOR]

Provides a means of understanding normal behavior and a wide spectrum of neuropsychological disorders. Discussion of neuropsychological evidence for a direct route to action; Actions and semantic decisions to words and pictures; Nature of the direct route.

We examined the relations between selection for perception and selection for action in a patient FK, with bilateral damage to his temporal and medial frontal cortices. The task required a simple grasp response to a common object (a cup) in the presence of a distractor (another cup). The target was cued by colour or location, and FK made manual responses. We examined the effects on performance of cued and uncued dimensions of both the target and the distractor. FK was impaired at perceptually selecting the target when cued by colour, when the target colour but not its location changed on successive trials. The effect was sensitive to the relative orientations of targets and distractors, indicating an effect of action selection on perceptual selection, when perceptual selection was weakly instantiated. The dimension-specific carry-over effect on reaching was enhanced when there was a temporal delay between a cue and the response, and it disappeared when there was a between-trial delay. The results indicate that perceptual and action selection systems interact to determine the efficiency with which actions are selected to particular objects. [ABSTRACT FROM AUTHOR]

We report data on the visual localisation ability of a patient with Balint's syndrome, GK. We show that, with relatively long exposures of displays, GK is better able to judge the spatial relations between separate objects (a "between-object judgement") than the spatial relations between a part and a whole object (a "within-object judgement") (Experiments 1–3). This dissociation occurred even when the same stimulus was used for both judgements, and the task instructions biased GK to parse the stimulus as either a single or as two separate objects (Experiments 2 and 6). However, when he could use a stored representation to make a within-object judgement, then performance was better than on a comparable spatial judgement of the relations between two separate objects (Experiments 4–7). The data demonstrate that stored representations of objects can support the spatial coding of parts to perceptual wholes. In the absence of stored representations, part-whole relations must be explicitly coded by attention, a process that is impaired in this patient. [ABSTRACT FROM AUTHOR]

We report a case study of a patient, FL, who shows symptoms of attentional dyslexia. He performs better at reading aloud single words than pairs of words, where he tends to make letter migration errors. These letter migrations are particularly prevalent from the word presented on the right into FL’s response to the word presented on the left. Performance on the word pair reading task is improved if the two words are presented in different cases or the space between them is increased. Further, FL performs better at reading a target word if he is only required to name the initial letter of a distractor word rather than read the whole word. However, single letter distractors then produce more interference than whole words. These findings are consistent with FL having poor letter location coding when attention is diffuse [Cognitive Neuropsychol. 18 (2001) 551; Cognitive Neuropsychol. 13 (1996) 205]. In addition, representations on the left side of his attentional space are particularly weak, and so vulnerable to stimuli on the right when FL adopts a wide spatial window for the task. The data point to a pre-categorical deficit in reading in this case. [Copyright &y& Elsevier]

We have presented a computational model called selective attention for identification model (SAIM), that can account for a broad range of psychological and neuropsychological phenomena on attention [1]. In this paper we report on work that extends SAIM to model data from visual search tasks. The results show that SAIM can capture important aspects of findings in visual search experiments, including variations of search slopes with the similarity between targets and distractors. SAIM is also capable of simulating experimental findings for redundant targets, including the violation of the Miller inequality. SAIM explains these experimental findings as the consequence of competitive processes involved in object identification. [Copyright &y& Elsevier]

Anti-extinction occurs when there is poor report of a single stimulus presented on the contralesional side of space, but better report of the same item when it occurs concurrently with a stimulus on the ipsilesional side (Goodrich & Ward, 1997). We report a series of experiments that examine the factors that lead to anti-extinction in a patient GK, who has bilateral parietal lesions but more impaired identification of left-side stimuli. We show a pattern of anti-extinction when stimuli are briefly presented, which is followed by an extinction effect when stimuli are left for longer in the visual field. In Experiments 1 and 2 we present evidence that the anti-extinction effects are determined by stimuli onsetting together, and it is not apparent when stimuli are defined by offsets. In Experiments 3 and 4 we report that performance is not strongly affected by whether the same or different tasks are performed on the ipsi- and contralesional stimuli, and the anti-extinction effect also survives trials where eye movements are made to right-side stimuli. Experiment 5 provides evidence that anti-extinction is due to temporal grouping between stimuli, rather than to increased arousal or cueing attention to the contralesional side. Experiment 6 demonstrates that anti-extinction dissociates from GK's conscious perception of when contra- and ipsilesional stimuli occur together. We interpret the data as indicating that there is unconscious and transient temporal binding in vision. [ABSTRACT FROM AUTHOR]

How do we detect a target in a cluttered environment? Here we present neuropsychological evidence that detection can be based on the action afforded by a target. A patient showing symptoms of unilateral neglect following damage to the right fronto-temporal-parietal region was slow and sometimes unable to find targets when they were defined by their name or even by a salient visual property (such as their color). In contrast, he was relatively efficient at finding a target defined by the action it afforded. Two other patients with neglect showed an opposite pattern; they were better at finding a target defined by its name. The data suggest that affordances can be effective even when a brain lesion limits the use of other properties in search tasks. The findings give evidence for a direct pragmatic route from vision to action in the brain. [ABSTRACT FROM AUTHOR]

We report two sets of data on object and action selection in a patient, ES, with an impaired ability to make task-based actions to objects. In simple action tasks, ES often made familiar actions to objects rather than the action appropriate to the task rule. We show that, despite having impaired selection of action, ES was able to select the target for action (based on salient perceptual differences). Relatively good object selection occurred even when the distractor had a stronger learned response than the target. In addition we show that distractors close to the path of action to a target can compete for, but are rejected from, selection along with any concurrently activated response. Suppression of an activated response improved performance, when the response would have been inappropriate to the task. [ABSTRACT FROM AUTHOR]

A single-case study is presented of a patient w ith a modality-specific problem in visual object recognition, w hich can be linked to impaired stored descriptions for objects. Performance was poor on tasks requiring naming, semantic decisions, and object decisions to seen objects. Performance on semantic decisions w ith w ords, however, was relatively good, demonstrating that the problem was not due solely to a general semantic impairment. Moreover, in contrast to the impairments in visual object recognition, both face recognition and on-line visual word recognition w ere within normal limits. The data indicate that im pairments of object recognition can be distinguished from impairments of face and visual w ord recognition, even when the problem can be localised within the structural description system for objects. We discuss the im plications of the results for understanding the relations between object, face, and word identification. [ABSTRACT FROM AUTHOR]

Assesses the manual interferences responses of direct action from a neuropsychological evidence. Determination of interference responses by stimulus familiarity and by spatial relations of the hand to the object; Effects of effectors and spatial uncertainty on interference responses.

Discusses the difficulty of measuring the perceptual experience of color, supporting the assertion that neuropsychological disorders of color processing. Information on within-subject analyses; Details on dissociation of color experience.

Abstract: Facial self-awareness is a basic human ability dependent on a distributed bilateral neural network and revealed through prioritized processing of our own over other faces. Using non-prosopagnosic patients we show, for the first time, that facial self-awareness can be fractionated into different component processes. Patients performed two face perception tasks. In a face orientation task, they judged whether their own or others’ faces were oriented to the left or right. In the ‘cross’ experiment, they judged which horizontal or vertical element in a cross was relatively longer while ignoring a task-irrelevant face presented as background. The data indicate that impairments to a distinct task-based prioritization process (when faces had to be attended) were present after brain damage to right superior frontal gyrus, bilateral precuneus, and left middle temporal gyrus. In contrast, impairments to automatic prioritization processes (when faces had to be ignored) were associated only with left hemisphere damage (the cingulate gyrus, superior parietal lobe, and superior temporal gyrus). In addition, both automatic and task-based self-prioritizations were affected by damage to left supramarginal and angular gyrus. The results for the gray matter analyses also extended to the adjacent white matter fiber tracts including the inferior occipital-frontal fasciculus, cingulum, and optic radiation. The data provide the first empirical evidence for separate functional roles of the left and right hemispheres in different aspects of self-face perception and suggest distinct functional processes respectively for paying attention to and for ignoring self-related information. [Copyright &y& Elsevier]

Abstract: The contribution of the left inferior prefrontal cortex in semantic processing has been widely investigated in the last decade. Converging evidence from functional imaging studies shows that this region is involved in the “executive” or “controlled” aspects of semantic processing. In this study, we report a single case study of a patient, PW, with damage to the right prefrontal and temporal cortices following stroke. PW showed a problem in executive control of semantic processing, where he could not easily override automatic but irrelevant semantic processing. This case, thus, shows the necessary role of the right inferior prefrontal cortex in executive semantic processing. Compared to tasks previously used in the literature, our tasks placed higher demands on executive semantic processing. We suggest that the right inferior prefrontal cortex is recruited when the demands on executive semantic processing are particularly high. [Copyright &y& Elsevier]

Humans'' unique aptitude for reasoning about mental states, known as Theory of Mind (ToM), can help explain the unique character of human communication and social interaction. ToM has been studied extensively in children, but there is no clear account of the cognitive basis of ToM in adults. Evidence from functional imaging and neuropsychology is beginning to address this surprising gap in our understanding, and this evidence is often thought to favour a domain-specific or modular architecture for ToM. We present a systematic approach to this issue for the paradigmatic case of belief reasoning, and argue that neuropsychological data provide no clear evidence for domain-specificity or modularity. Progress in understanding ToM requires new tasks that isolate potentially distinct components of this complex ability. [Copyright &y& Elsevier]

There are only a few studies on the brain networks involved in the ability to prepare in time, and most of them followed a correlational rather than a neuropsychological approach. The present neuropsychological study performed multiple regression analysis to address the relationship between both grey and white matter (measured by magnetic resonance imaging in patients with brain lesion) and different effects in temporal preparation (Temporal orienting, Foreperiod and Sequential effects). Two versions of a temporal preparation task were administered to a group of 23 patients with acquired brain injury. In one task, the cue presented (a red versus green square) to inform participants about the time of appearance (early versus late) of a target stimulus was blocked, while in the other task the cue was manipulated on a trial-by-trial basis. The duration of the cue-target time intervals (400 versus 1400 ms) was always manipulated within blocks in both tasks. Regression analysis were conducted between either the grey matter lesion size or the white matter tracts disconnection and the three temporal preparation effects separately. The main finding was that each temporal preparation effect was predicted by a different network of structures, depending on cue expectancy. Specifically, the Temporal orienting effect was related to both prefrontal and temporal brain areas. The Foreperiod effect was related to right and left prefrontal structures. Sequential effects were predicted by both parietal cortex and left subcortical structures. These findings show a clear dissociation of brain circuits involved in the different ways to prepare in time, showing for the first time the involvement of temporal areas in the Temporal orienting effect, as well as the parietal cortex in the Sequential effects. [ABSTRACT FROM AUTHOR]

Abstract: Recently, it has been shown that patients with visual extinction can show enhanced awareness of contralesional stimuli that match the contents of working memory [Soto, D., & Humphreys, G.W. (2006). Proceedings of the National Academy of Sciences, USA, 103, 4789–4792]. Here we investigate whether these effects extend to cases where the working memory cue is verbal rather than visual (Study 1), and we show that non-spatial cues can overcome problems in spatial disengagement in patients, and this can affect the first eye movement made in search (Study 2). We discuss the implications of the data for understanding the relations between the cueing of attention from visual and conceptual information held in working memory and the cueing of spatial attention, and for understanding the relations between non-spatial and spatial biases in selection. [Copyright &y& Elsevier]

Abstract: Memory and attention interact. Information held in working memory (WM) can bias visual selection toward matching stimuli in a subsequent search display, while a search target that is different from the memory stimulus can interfere with its subsequent recognition. In recent fMRI studies, the pulvinar has been consistently shown to have an enhanced response when an item in WM matches a search target and a reduced response when the WM item matches a distracter in search. Here we used Granger causality analysis to help understand the role of the pulvinar in resolving competition between memory and selection processes. Across three experiments the results showed increased coupling between the pulvinar and the ipsilateral superior frontal gyrus, contralateral temporal–parietal junction (TPJ) and calcarine sulcus when a visual search distracter matched the item held in memory. This connection pattern suggests that the pulvinar suppresses visual responses to the target when a contralateral distracter contains information held in working memory. We propose that this suppression acts to protect the memory item from interference arising from information associated with the search target. Consistent with this proposal we showed that the strength of the thalamus-to-visual connection predicted performance on a subsequent memory test. The data therefore suggest that the thalamus modulates bottom up processing in sensory cortex to minimize interference to WM content. [Copyright &y& Elsevier]

We present the case for a role of biologically plausible neural network modeling in bridging the gap between physiology and behavior. We argue that spiking-level networks can allow "vertical" translation between physiological properties of neural systems and emergent `whole-system" performance- enabling psychological results to be simulated from implemented networks and also inferences to be made from simulations concerning processing at a neural level. These models also emphasize particular factors (e.g. the dynamics of performance in relation to real-time neuronal processing) that are not highlighted in other approaches and that can be tested empirically. We illustrate our argument from neural-level models that select stimuli by biased competition. We show that a model with biased competition dynamics can simulate data ranging from physiological studies of single-cell activity (Study 1) to whole-system behavior in human visual search (Study 2), while also capturing effects at an intermediate level, including performance breakdown after neural lesion (Study 3) and data from brain imaging (Study 4). We also show that, at each level of analysis, novel predictions can be derived from the biologically plausible parameters adopted, which we proceed to test (Study 5). We argue that, at least for studying the dynamics of visual attention, the approach productively links single-cell to psychological data. [ABSTRACT FROM AUTHOR]

Abstract: Previous research has suggested that, when operating in a distributed attention mode, the visual system automatically represents visual displays by their overall statistics, rather than their individual properties. Recent neuropsychological work shows partly preserved distributed attention in simultanagnosic patients, who are typically defined as only perceiving one object at a time. Here we assessed whether GK, a patient with simultanagnosia, shows averaging of stimulus properties when distributing his attention across a set of items. We manipulated different stimulus properties in two experiments: color shades and size. We found that, when GK was in a distributed mode of attention, he (incorrectly) identified the mean object from two classes of exemplars more than in a control condition, when only one exemplar class was present. Overall, this study suggests that automatic statistical processing of color and size is possible in simultanagnosia. [Copyright &y& Elsevier]