From both sides now: crossover effects influence navigation in patients with unilateral neglect.

Unilateral neglect is a challenging disorder that pervades a range of behaviours following stroke and hampers recovery. Although a preponderance of clinical studies measure performance on a range of bedside assessments, including line bisection and cancellation tasks, there have been calls for studies to embrace more relevant functional measures. Here, for the first time, we present data from two separate tasks that characterise the performance of seven patients with unilateral neglect when navigating a power wheelchair. The tasks involved negotiating an obstacle course and steering a central path between gaps of different sizes. Results from the obstacle course confirmed the clinical observation and predicted bias of contralesional errors. However, the second task revealed a robust "crossover" effect. Patients deviated to the ipsilesional side for large gaps but deviated increasingly contralesionally when steering through small gaps in behaviour that was analogous to that previously shown on line bisection tasks. Contrary to being seen as an unintuitive finding, further analysis of these errors suggests that patients are giving disproportionate weight to the location of the ipsilesional object when plotting a midline course between two objects. Our results provide a platform for further studies to investigate the modulation and rehabilitation of this important skill.

Detection by action: neuropsychological evidence for action-defined templates in search.

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.

Preliminary validation study of the Russian Birmingham Cognitive Screen.

INTRODUCTION: The Birmingham Cognitive Screen (BCoS) is designed for use with individuals who have acquired language impairment following stroke. Our goal was to develop a Russian version of the BCoS (Rus-BCoS) by translating the battery following cultural and linguistic adaptations and establishing preliminary data on its psychometric properties. METHOD: Fifty patients with left-hemisphere stroke were recruited, of whom 98% were diagnosed with mild to moderate aphasia. To check whether the Rus-BCoS provides stable and consistent scores, internal consistency, test-retest, and interrater types of reliability were determined. Eight participants with stroke and 20 neurologically intact participants were assessed twice. To inspect the discriminative power of the battery, 63 participants without brain impairment were tested with the Rus-BCoS. Additionally, the Russian version of the Montreal Cognitive Assessment (MoCA), Quantitative Assessment of Speech in Aphasia, and Luria's Neuropsychological Assessment Battery were used to examine convergent validity, sensitivity, and specificity of the Rus-BCoS. RESULTS: The internal consistency as well as test-retest and interrater reliability of the Rus-BCoS satisfied criteria for the research use. Performance on a majority of tasks in the battery correlated significantly with independently validated tests that putatively measure similar cognitive processes. Critically, all patients with aphasia returned nonzero scores in at least one task in all the Rus-BCoS sections, with the exception of the Controlled Attention section where two patients with severe executive control deficits could not perform. CONCLUSIONS: The Rus-BCoS shows promise as a comprehensive cognitive screening tool that can be used by clinicians working with Russian-speaking persons experiencing poststroke aphasia after much further validation and development of reliable normative standards. Given a lack of quantitative neuropsychological assessment tools in Russia, however, we contend the Rus-BCoS offers potential benefits to clinicians and patients. However, data from research studies with a broader sample of Russian speakers are needed.

Domain-specific versus generalized cognitive screening in acute stroke.

Cognitive assessments after stroke are typically short form tests developed for dementia that generates pass/fail classifications (e.g. the MoCA). The Oxford Cognitive Screen (OCS) provides a domain-specific cognitive profile designed for stroke survivors. This study compared the use of the MoCA and the OCS in acute stroke with respect to symptom specificity and aspects of clinical utility. A cross-sectional study with a consecutive sample of 200 stroke patients within 3 weeks of stroke completing MoCA and OCS. Demographic data, lesion side and Barthel scores were recorded. Inclusivity was assessed in terms of completion rates and reasons for non-completion were evaluated. The incidence of cognitive impairments on both the MoCA and OCS sub-domains was calculated and differences in stroke specificity, cognitive profiles and independence of the measures were addressed. The incidence of acute cognitive impairment was high: 76% of patients were impaired on MoCA, and 86% demonstrated at least one impairment on the cognitive domains assessed in the OCS. OCS was more sensitive than MoCA overall (87 vs 78% sensitivity) and OCS alone provided domain-specific information on prevalent post-stroke cognitive impairments (neglect, apraxia and reading/writing ability). Unlike the MOCA, the OCS was not dominated by left hemisphere impairments but gave differentiated profiles across the contrasting domains. The OCS detects important cognitive deficits after stroke not assessed in the MoCA, it is inclusive for patients with aphasia and neglect and it is less confounded by co-occurring difficulties in these domains.

Don't think twice, it's all right--contralesional dependency for bimanual prehension movements.

In bimanual coordination when moving the hands to two separate objects, subjects tend to initiate and terminate the movements together, even when the targets are at different distances or are of a different size. Additionally, each hand tends to scale its grasp independently to the object to be grasped. Here, we report the performance of a patient, who had previously shown signs of motor neglect, on two experiments investigating coupling and independence in bimanual coordination. The patient showed relatively normal bimanual behaviour for the transport phase of prehension when objects were placed at different distances (Experiment 1), but abnormal behaviour for the grasp component when objects were of different sizes (Experiment 2). Moreover, the contralesional limb demonstrated a dependency of grasp that was related to the object grasped by the ipsilesional limb. We discuss the possible underlying mechanisms of this dependency in relation to competitive motor programming and attentional bias. The results also reinforce the view that the transport and grasp components of prehension are distinct processes.

The effect of cueing on unilateral neglect.

Heilman and Valenstein recently failed to reduce unilateral neglect, assessed by a line bisection task, by cueing patients to attend to their neglected field. Cueing was accomplished by placing letters at both ends of the line and instructing subjects to identify either the right or left hand letter prior to bisecting the line. The present experiments tested whether this failure to improve neglect occurred because patients were presented with competing stimuli in their neglected and non-neglected fields. Five patients with unilateral neglect and hemianopia took part in two experiments. The results showed a marked decrease in neglect when subjects were cued and forced to report stimuli in their neglected field. This occurred even when there was a competing stimulus in the non-neglected field. However, in the absence of forced report requirements, patients oriented to stimuli in the non-neglected field. The results are interpreted as a failure of patients with unilateral neglect to orient automatically to the side of space contralateral to the lesion, though processes governing the conscious orienting of attention are intact.

Expression is computed separately from facial identity, and it is computed separately for moving and static faces: neuropsychological evidence.

We report data contrasting the processing of facial identity from static photographs, and facial expression from static and moving images, in two patients with face processing impairments. One patient is markedly impaired at perceiving facial identity and he is poor at discriminating facial expression and gender from static photographs of faces. In contrast, he performs normally when required to make judgements of facial expression and gender to faces depicted by sets of moving light dots. The second patient is relatively good at perceiving facial identity, but poor at judging emotional expression from both static and moving faces. The data are consistent with the existence of separate processes for encoding face identity and facial expression, and, furthermore, indicate the separate encoding of expression from moving and static images.

An experimental analysis of unintentional lower limb action.

We provide an experimental analysis of the factors that determine unintentional lower limb action in a patient with cortico-basal degeneration. We show a dissociation between lower limb movements in a novel task and the ability to remember task instructions. In addition, there were effects of the pre-potency of the learned response to the stimulus, with different effects emerging with familiar and unfamiliar stimuli.

Recognition impairments and face imagery.

We investigated face imagery for H.J.A. and P.H., who experience profound difficulties in recognising familiar faces. H.J.A.'s problems involve a perceptual impairment that compromises the integration of features into a coherent representation, and he does not show covert recognition of faces in indirect tests. In contrast, P.H. has shown extensive covert recognition effects, leading to the suggestion that his deficit occurs at a higher level of visual processing than H.J.A.'s. H.J.A. and P.H. were given tasks intended to explore their ability to answer questions that depended on imaging single faces, and on configuration-based or feature-based comparisons of imaged sets of three faces. For all of these face imagery tasks, P.H.'s overall performance was severely impaired. H.J.A., though, showed preserved face imagery when imaging single faces and when making feature-based comparisons between imaged faces. However, when configuration-based comparisons were demanded H.J.A. also showed a severe and stable impairment of face imagery. These observations are inconsistent with the idea that face recognition impairments have a unitary underlying cause and vary only in severity. Instead, they imply multi-stage causation, with the nature of consequent impairments of face imagery being determined by the level at which the recognition deficit arises.

Neuropsychometric outcome following aortic arch surgery: a prospective randomized trial of retrograde cerebral perfusion.

BACKGROUND: Aortic surgery requiring hypothermic circulatory arrest is associated with a high incidence of brain injury. However, knowledge of neuropsychometric outcome is limited. Retrograde cerebral perfusion has become a popular adjunctive technique to hypothermic circulatory arrest. The aim of this study was to assess neuropsychometric outcome and compare the 2 techniques. METHODS: In a prospective randomized trial, 38 patients requiring elective aortic arch surgery were allocated to either hypothermic circulatory arrest plus retrograde cerebral perfusion or hypothermic circulatory arrest alone. Neuropsychometric testing was performed preoperatively, and at 6 weeks and 12 to 24 weeks postoperatively. Deficit was defined as a 20% decline in 2 tests or more. Standardized Z scores were calculated for each patient and test. Eighteen patients underwent hypothermic circulatory arrest and 20 patients underwent hypothermic circulatory arrest plus retrograde cerebral perfusion. The mean cardiopulmonary bypass, hypothermic circulatory arrest, and retrograde cerebral perfusion durations were 169, 30, and 25 minutes, respectively. RESULTS: There were 2 deaths and 2 neurological deficits. At 6 weeks postoperatively, 77% of the hypothermic circulatory arrest group and 93% of the hypothermic circulatory arrest plus retrograde cerebral perfusion group had a deficit (P =.22). At 12 weeks this was reduced to 55% and 56%, respectively (P =.93). There was a worse total Z test score in the hypothermic circulatory arrest plus retrograde cerebral perfusion group at 12 weeks (P =.05). Neuropsychometric change did not correlate with hypothermic circulatory arrest duration, presence of aortic atheroma, cannulation technique, or procedure. CONCLUSIONS: Hypothermic circulatory arrest plus/minus retrograde cerebral perfusion is associated with a high incidence of neuropsychometric change despite ostensibly normal clinical outcomes and apparently safe arrest duration. Retrograde cerebral perfusion did not improve outcome in this small study.

Grouping processes in visual search: effects with single- and combined-feature targets.

We report evidence for spatially parallel visual search for targets defined by combinations of form elements in visual search. In Section 1, we show that flat search functions occur for combined-form targets when distractor forms are homogeneous and can be grouped together, thus segmenting the target from the distractors. Introducing heterogeneous distractors lessens distractor grouping and can produce serial search. These results cannot be easily attributed to subjects' use of local feature information to discriminate targets. Instead, they suggest that grouping can operate at a level at which combined form information is represented. In Section 2 we show that these grouping effects are spatially scaled by the size of the stimuli. In Section 3 we show that heterogeneity does not prevent flat search functions when the target has a unique defining feature. The data are interpreted in terms of a hierarchical processing system involving both devoted single-feature and combined-feature (junction) maps. Grouping processes can operate at both the single-feature and the combined-form levels. Selection in visual search remains confined to one object description at a time, but this description can be at various spatial scales, including that at the level of grouped forms.

Parallel computation of primitive shape descriptions.

This article reports evidence that parallel search functions can occur when heterogeneous conjunction elements configure into a single object description. Experiment 1 demonstrates parallel search for form conjunctions presented in displays of heterogeneous nontargets when closure and good continuation between display elements are exhibited. When closure and good continuation are absent, reaction times increase linearly with set size (Experiment 2). Experiment 3 demonstrates a halfway stage between these two extremes, in which displays have closure but not good continuation. Finally, selection of object descriptions is shown to be temporally limited to one object at a time (Experiment 4). The data are incompatible with both local feature-based and distractor similarity-based accounts of visual search; however, they are compatible with there being an important role for preattentive feature combinations forming primitive object descriptions. Parallel search functions can occur when heterogeneous conjunctions configure into a single object description.

Luminance and edge information in grouping: a study using visual search.

Preattentive grouping is supported by 2 systems, a brightness system that is contrast polarity sensitive and an edge system that is relatively insensitive to contrast polarity. Search was spatially parallel for pairs of same contrast polarity vertically aligned circles, among horizontal pairs, and serial for pairs of circles that had the opposite contrast polarity (Experiments 1-3). By replacing the circles with squares, the authors investigated the effect of adding collinear edge information. When collinear edges were present, the polarity difference between paired items did not disrupt grouping (Experiments 4-6). These results support models of grouping in which brightness and edge information are processed separately (e.g., S. Grossberg & E. Mingolla, 1985) and models of visual search in which complex relations between stimuli can be computed in parallel across the display.

Knowing what you need but not what you want: affordances and action-defined templates in neglect.

We examined search for target objects in a patient, MP, showing symptoms of left unilateral neglect. The conditions varied how the target was defined, the numbers of targets and distractors, and whether search was for multiple or single targets. We found that search was substantially improved when the target was defined by a description of its action rather than its name. This advantage for action-defined targets increased with larger display sizes. For both action and name-defined targets, there were also larger effects of the number of distractors when search was for multiple rather than single targets, even when the numbers of distractors were kept constant. However, these effects were increased for name-defined targets. The differences between action- and name-defined targets decreased when objects were replaced with words. The data suggest that search could be based on action-defined templates of targets, activated by affordances from objects. The action-defined templates facilitated detection and reduced MP's tendency to re-search displays.

Mu rhythm desynchronization reveals motoric influences of hand action on object recognition.

We examined the effect of hand grip on object recognition by studying the modulation of the mu rhythm when participants made object decisions to objects and non-objects shown with congruent or incongruent hand-grip actions. Despite the grip responses being irrelevant to the task, mu rhythm activity on the scalp over motor and pre-motor cortex was sensitive to the congruency of the hand grip-in particular the event-related desynchronization of the mu rhythm was more pronounced for familiar objects grasped with an appropriate grip than for objects given an inappropriate grasp. Also the power of mu activity correlated with RTs to congruently gripped objects. The results suggest that familiar motor responses evoked by the appropriateness of a hand grip facilitate recognition responses to objects.

Effects of action relations on the configural coding between objects.

Configural coding is known to take place between the parts of individual objects but has never been shown between separate objects. We provide novel evidence here for configural coding between separate objects through a study of the effects of action relations between objects on extinction. Patients showing visual extinction were presented with pairs of objects that were or were not co-located for action. We first confirmed the reduced extinction effect for objects co-located for action. Consistent with prior results showing that inversion disrupts configural coding, we found that inversion disrupted the benefit for action-related object pairs. This occurred both for objects with a standard canonical orientation (e.g., teapot and teacup) and those without, but where grasping and using the objects was made more difficult by inversion (e.g., spanner and nut). The data suggest that part of the affordance effect may reflect a visuo-motor response to the configural relations between stimuli. Experiment 2 showed that distorting the relative sizes of the objects also reduced the advantage for action-related pairs. We conclude that action-related pairs are processed as configurations.

I can see what you are doing: Action familiarity and affordance promote recovery from extinction.

We assessed the effects of three factors on recovery from extinction in patients with lesions including the posterior parietal lobe: (a) whether objects were frequently used together in action versus whether they could be used in action together; (b) whether there was an effect of positioning objects for action; and (c) whether the surface properties of objects mediated performance. There was greater recovery from extinction for objects used frequently together, along with effects produced by objects that could be used together. There were also positive effects of correctly positioning objects for action. There were no effects of surface information on the benefit of reporting both members of a pair, though there were some effects on error trials. The results provide positive evidence for an effect on attention of affordances based on objects falling in plausible co-locations for action. Such affordances may also be influenced by the frequency with which objects are used together and can be generated from edge-based representations of objects (surface colour and depth are not necessary). However, surface-based representations may influence the speed with which action-related properties of objects engage attention.

Bimanual coordination and perceptual grouping in a patient with motor neglect.

Motor neglect refers to the underutilisation of a limb contralateral to a brain lesion in the absence of primary motor and sensory deficits. The related problem of motor extinction refers to a contralesional motor deficit that worsens or only becomes apparent when bilateral actions are required. We present a single case (MM) of a patient with motor neglect who also demonstrates a form of motor extinction that is influenced by visual grouping between stimuli. The comparisons of unimanual and bimanual reach to grasp movements towards one or two objects in Experiment 1 showed that MM made relatively normal unimanual contralesional movements but impaired contralesional movements under bimanual action conditions. Experiment 2 demonstrated that motor extinction was improved by asking MM to make bimanual movements towards a single object. In Experiment 3, the effects of object coding on bimanual movement were replicated across conditions that varied the distance between end points for the movements. MM did not show overt visual extinction. We suggest that MM demonstrates a late-acting attentional bias that is expressed in terms of competitive motor activity. Normally, the contralesional limb "loses" the competition for action, but this can be modulated by visual grouping between targets.

Object identification in simultanagnosia: When wholes are not the sum of their parts.

We examined object identification in two simultanagnosic patients, ES and GK. We show that the patients tended to identify animate objects more accurately than inanimate objects (Experiments 1 and 4). The patients also showed relatively good identification of objects that could be recognised from their global shape, but not objects whose recognition depended on their internal detail (Experiment 2). Indeed, the presence of local segmentation cues disrupted global identification (Experiment 3). Identification was aided, though, by the presence of surface colour and texture (Experiment 4). We suggest that the patients could derive global representations of objects that served to recognise animate items. In contrast, they were impaired at coding parts-based representations for the identification of inanimate objects.

Position-matching in the upper limb: professional ballet dancers perform with outstanding accuracy.

OBJECTIVES: To investigate the accuracy in position-matching in the upper limb in two groups of subjects who were physically fit and movement aware. DESIGN: A mixed-group design was used. Objective measurement of the accuracy in position-matching at the shoulder and elbow in both dominant and nondominant arms consisted of photographic record of the position-matching test, with goniometric measurement. SETTINGS: Physiotherapy department at the Birmingham Royal Ballet and School of Health Science, University of Birmingham. SUBJECTS: Two subject groups: physiotherapy students (n = 10), professional ballet dancers (n = 10). RESULTS: A mixed design analysis of variance found significant differences between the accuracy in position-matching at both the shoulder and elbow joints in the two groups (p < 0.05), with the ballet dancers having greater accuracy then the physiotherapy students. A significant difference in the joint positions tested were demonstrated (p < 0.05) with the positions of abduction at the shoulder and extension of the elbow showing greatest accuracy in matching. There was no significant difference found between the dominant and nondominant upper limb in position-matching. CONCLUSION: Professional ballet dancers demonstrated greater accuracy in position-matching the upper limb, implying that mass and continuing practice can improve a motor sensory skill.