Left Spatial Neglect Research Articles

Effectiveness of Cognitive Rehabilitation for Left Unilateral Spatial Neglect

Effectiveness of Cognitive Rehabilitation for Left Unilateral Spatial Neglect

Bilateral impairment of concurrent saccade programming in hemispatial neglect

When healthy observers make a saccade that is erroneously directed toward a distracter stimulus, they often produce a corrective saccade within 100ms after the end of the primary saccade. Such short inter-saccadic intervals indicate that programming of the secondary saccade has been initiated prior to the execution of the primary saccade and hence that the two saccades have been programmed concurrently. Here we show that concurrent saccade programming is bilaterally impaired in left spatial neglect, a strongly lateralized disorder of visual attention resulting from extensive right cerebral damage. Neglect patients were asked to make saccades to targets presented left or right of fixation while disregarding a distracter presented in the opposite hemifield. We examined those experimental trials on which participants first made a saccade to the distracter, followed by a secondary (corrective) saccade to the target. Compared to healthy and right-hemisphere damaged control participants the proportion of secondary saccades directing gaze to the target instead of bringing it even closer to the distracter was bilaterally reduced in neglect patients. In addition, the characteristic reduction of secondary saccade latency observed in both control groups was absent in neglect patients, whether the secondary saccade was directed to the left or right hemifield. This pattern is consistent with a severe, bilateral impairment of concurrent saccade programming in left spatial neglect.

The spatial encoding of body parts in patients with neglect and neurologically unimpaired participants

Body parts are represented in the brain in a very specific fashion, as compared to other three-dimensional objects, with reference to their prototypic shape and multisensory coding. However, evidence is lacking about the spatial representation of body parts. To address this issue, in Experiment 1 we first compared the metric representation of body parts and of non-bodily objects in 14 right-brain-damaged patients with left unilateral spatial neglect (USN), and in 14 neurologically unimpaired control participants. Participants bisected, by manual pointing, a three-dimensional object, or their own left forearm. Patients showed the well-known ipsilesional rightward displacement of the subjective midpoint, in both forearm and solid bisection. Both USN patients and control participants were overall more accurate in the bisection of their own forearm, relative to the extracorporeal object. In four patients this advantage of the forearm was significant in a single-case analysis, while two patients showed the opposite dissociation, being more accurate with the solid object. In Experiment 2 neurologically unimpaired participants were more accurate in the bisection of a fake forearm, as well as of their own forearm, as compared to the extrapersonal object. Overall, the results indicate that the representation of the metric of the body is more reliable than that of extrapersonal objects, and also more resistant to the disruption of spatial representations brought about by USN, possibly due to the prototypical shape of body parts. Furthermore, the double dissociation found in USN patients suggests that the metrics of body parts and of extrapersonal objects are supported by independent spatial processes.

PO04-MO-21 Transcortical motor aphasia, left spatial neglect, and limb and magnetic apraxia due to right anterior cerebral artery infarction: a case report

PO04-MO-21 Transcortical motor aphasia, left spatial neglect, and limb and magnetic apraxia due to right anterior cerebral artery infarction: a case report

Parietal versus temporal lobe components in spatial cognition: Setting the mid‐point of a horizontal line

Recent anatomo-clinical correlation studies have extended to the superior temporal gyrus, the right hemisphere lesion sites associated with the left unilateral spatial neglect, in addition to the traditional posterior-inferior-parietal localization of the responsible lesion (supramarginal gyrus, at the temporo-parietal junction). The study aimed at teasing apart, by means of repetitive transcranial magnetic stimulation (rTMS), the contribution of the inferior parietal lobule (angular gyrus versus supramarginal gyrus) and of the superior temporal gyrus of the right hemisphere, in making judgments about the mid-point of a horizontal line, a widely used task for detecting and investigating spatial neglect. rTMS trains at 25 Hz frequency were delivered over the inferior parietal lobule (angular gyrus and supramarginal gyrus), the superior temporal gyrus and the anterior parietal lobe of the right hemisphere, in 10 neurologically unimpaired participants, performing a line bisection judgment task. rTMS of the inferior parietal lobule at the level of the supramarginal gyrus brought about a rightward error in the bisection judgment, ipsilateral to the side of the rTMS, with stimulation over the other sites being ineffective. The neural correlates of computing the mid-point of a horizontal segment include the right supramarginal gyrus in the inferior parietal lobule and do not extend to the angular gyrus and the superior temporal gyrus. These rTMS data in unimpaired subjects constrain the evidence from lesion studies in brain-damaged patients, emphasizing the major role of a subset of relevant regions.

Monocular patching affects inattention but not perseveration in spatial neglect

Monocular patching might improve perceptual-attentional, not motor-intentional deficits in a patient with chronic post-stroke left spatial neglect. Performing a line-cancellation task, his omission errors were associated with a perceptual-attentional ‘where’ deficit, while perseverative errors were associated with ‘aiming’ motor-intentional bias. Contralesional patching had no effect on the omissions (p = .871), whereas ipsilesional patching reduced left-sided omissions compared with the unpatched condition (p = .016). Neither patching condition altered perseverative errors. Further research is needed to examine whether targeting treatments to spatial neglect symptoms (omissions, perseveration) results in improved outcomes.

Acute hemianopic patients do not show a contralesional deviation in the line bisection task

JO N 3148 control subjects. Our objectives were twofold: (i) if adaptive attentional mechanisms are responsible for the LBE in hemianopic patients it may be absent in their acute stage, and if so (ii) is the line bisection task a reliable bedside tool to distinguish hemianopia from hemineglect in the acute stage of stroke? All participants (n = 21) gave their informed written consent according to the Declaration of Helsinki. Mean age (years/±SD) did not differ significantly between healthy control subjects (controls, n = 8, 56.6 ± 18.9), left hemianopic patients (LH, n = 5, 61.0 ± 10.4), right hemianopic patients (RH, n = 4, 58.0 ± 20.1) and patients with left spatial neglect (n = 4, 60.5 ± 11.3). Acute (< 1 month) unilateral stroke was confirmed by MRI. The hemianopic visual field defects, complete and incomplete, respectively, were assessed using the manual Goldmann perimeter (Table 1). Ophthalmological examination revealed corrected visual Bjorn Machner Andreas Sprenger Urban Hansen Wolfgang Heide Christoph Helmchen

P02-176 A case report of Asperger Syndrom with associated visuo-attentional disorders

In Pervasive Developmental Disorders, visual perception deficits, such as impaired face and object recognition, have been previously described. More particularly, Kracke (1994) as well as Pietz and colleagues (2003) reported prosopagnosia in individuals fulfilling criteria for Asperger Syndrome (AS). Moreover, anatomical or functional anomalies in the temporo-occipital areas have been observed in neuroimaging studies in autistic patients. Besides, this region is known to underlie visuo-attentional functions. Yet, the examination of such cognitive functions in autistic disorders is scarce, even in clinical practice.This poster presents the case study of a teenager (male, 14 years) diagnosed with AS on the basis of his developmental history and current presentation: marked social abnormalities, lack of ocular contact, good language although with verbal and non-verbal communication difficulties, circumscribed special interests and motor impairments.A neuropsychological and neuroophtalmological assessment of visuo-attentional cognitive functions revealed a visual field concentric reduction, signs of left unilateral spatial neglect, impaired visual pursuit, visuo-constructive apraxia and visual extinction. The anatomical MRI showed a mild enlargement of the left posterior ventricular horn (facing the occipital lobe), probably consecutive to a cortical atrophy (in the occipito-parietal parenchyma).This case study emphasizes that visuo-attentional cognitive difficulties such as visual recognition deficit, visual field defect and attentional bias may be associated to behavioural signs of AS. In addition to previous descriptions in the literature, our case study leads us to consider that neuropsychological assessments of visuo-attentional functions in children with autistic symptoms may provide invaluable clinical and theoretical information.

Effectiveness of Training for 54 Patients with Left Unilateral Spatial Neglect

Effectiveness of Training for 54 Patients with Left Unilateral Spatial Neglect

Abnormal Attentional Modulation of Retinotopic Cortex in Parietal Patients with Spatial Neglect

Brain regions beyond visual cortex are thought to be responsible for attention-related modulation of visual processing [1, 2], but most evidence is indirect. Here, we applied functional magnetic resonance imaging (fMRI), including retinotopic mapping of visual areas, to patients with focal right-parietal lesions and left spatial neglect [3, 4]. When attentional load at fixation was minimal, retinotopic areas in right visual cortex showed preserved responses to task-irrelevant checkerboards in the contralateral left hemifield, analogously to left visual cortex for right-hemifield checkerboards, indicating a "symmetric" pattern in both hemispheres with respect to contralateral stimulation under these conditions. But when attentional load at fixation was increased, a functional asymmetry emerged for visual cortex, with contralateral responses in right visual areas being pathologically reduced (even eliminated for right V4/TEO), whereas left visual areas showed no such reduction in their contralateral response. These results reveal attention-dependent abnormalities in visual cortex after lesions in distant (parietal) regions. This may explain otherwise puzzling aspects of neglect [5, 6], as confirmed here by additional behavioral testing.

3D left hyperschematia after right brain damage

A quantitative assessment of a distortion involving the left side of space, both in two-dimensional (drawing), and three-dimensional (modeling), visuo-constructional tasks is reported in a patient with a right temporoparieto-occipital lesion, and left hemianopia, without visuospatial neglect. In drawing and clay modeling of objects the patient exhibited a disproportionate enlargement of the left-hand side of objects. Matching perceptually two rectangles, the patient underestimated the left side of the stimulus. In a visuomotor task requiring the reproduction of horizontal extent, the patient exhibited a leftward overextension. Observations in two right-brain-damaged patients by Rode, Michel, Rossetti, Boisson, and Vallar (2006, Neurology, 67, 1801) are confirmed and extended. The patient's impairment may involve a disordered representation of extrapersonal space, with a leftward disproportionate expansion of the spatial medium (‘hyperschematia’). Accordingly, symmetrical productions are compensatorily expanded leftwards, and the left sides of objects are perceived as smaller in horizontal extent. The disorder is largely independent of left spatial neglect.

When the whole is more than the sum of the parts: Evidence from visuospatial neglect

One possible pathological mechanism underlying the rightward bisection error of right-brain-damaged patients with left spatial neglect is a leftward relaxation of the spatial representational medium. This view was originally based on the finding that patients with left neglect, required to extend horizontal segments, in order to double their original length, may exhibit a relative left overextension of the drawn lines (Bisiach et al., 1994). We investigated this putative distortion of representational space using a 16 cm 'line segmentation' task (Experiment I). Were the representation of space relaxed contralesionally, a progressive increase from right to left of the size of the drawn segments would be expected. Right-brain-damaged patients with left unilateral neglect (N=12) performed the segmentation task with no left versus right differences, as right-brain-damaged patients without neglect (N=8), and neurologically unimpaired control subjects (N=10), did. Experiments 2 and 3 explored the effects of sample length (1, 2, 4, and 8cm), by which the 16cm lines had to be segmented. Neglect patients produced longer left-sided segments only for the 8 cm sample (i.e. half of the length of the segment). This set of experiments suggests an impairment in the segmentation task only with the larger (8 cm) sample, when a more global level of processing may be involved. Experiment 4 assessed this hypothesis by a 'part/whole' bisection task, using 8 cm lines, presented either embedded in a longer 16 cm line or in isolation. Neglect patients made a larger rightward bisection error when the segment was not embedded. The suggestion is made that the lateral distortion of the representation of space in neglect patients (i.e., a leftward relaxation of the spatial medium) concerns tasks where a more 'global' representation of the visual stimulus has to be set up. The different demands of the segmentation and bisection tasks are discussed.

Decrease in blood pressure after intravenous administration of urapidil during recombinant tissue plasminogen activator thrombolysis for acute ischemic stroke

Background: In patients who are candidates for IV recombinant tissue plasminogen activator (rtPA) thrombolysis for the treatment of acute ischemic stroke, blood pressure (BP)-lowering therapy is sometimes needed for systolic BP >185 mm Hg or diastolic BP >110 mm Hg. However, there is vast uncertainty regarding the appropriate choice of an antihypertensive agent. Case summary: A 68-year-old Algerian woman (height, 161 cm; weight, 68 kg; body mass index, 26 kg/m 2) was admitted to the Cardiology Unit of Amiens University Hospital, Amiens, France, for the assessment of nonvalvular atrial fibrillation. She was prescribed furosemide 40 mg/d to treat a slight left cardiac insufficiency. On day 10 of admission, the patient developed left-sided weakness. Neurologic examination revealed left hemiparesis. A computed tomography scan of the head showed no abnormality. Approximately 90 minutes after onset of the neurologic deficit, the patient had a BP of 180/100 mm Hg in both arms, an irregular pulse >75 bpm, and normal heart sounds. The patient was transferred to the Neurovascular Unit. There were no cervical or femoral bruits in this patient. During neurologic examination, the patient was alert and showed no signs of major cognitive deficit. The neurologic examination did reveal, however, minor hemisphere syndrome with left spatial neglect. There was a left lower-facial paresis. Motor examination revealed normal bulk with diminished tone in the patient's left arm and leg. Although there were no physical signs of dehydration, laboratory results revealed moderate signs of dehydration (total protein, 91 g/L [indicating proteinemia]; sodium, 147 mmol [indicating hypernatremia]; and elevated hematocrit, 42.0%). Considering the diagnosis of ischemic stroke and the duration of the symptoms (<3 hours), IV rtPA was administered. Approximately 10 minutes after intravenous rtPA administration, the patient's BP was 210/110 mm Hg, and an IV bolus of urapidil (20 mg) was administered. Approximately 2 minutes following urapidil administration, the patient developed neurologic worsening indicated by left-sided hemiplegia. Her BP was 105/60 mm Hg. The IV rtPA was immediately discontinued and volume replacement was started for 20 minutes. IV rtPA was restarted after the patient remained hemodynamically stable (15 minutes after rtPA was restarted). Following intensive physiotherapy, the patient was discharged on anticoagulation with a favorable outcome. At her 6-month follow-up, the patient had fully recovered. Conclusion: We report a probable case of hypotension associated with IV bolus of urapidil administration during rtPA thrombolysis for acute ischemic stroke in an elderly patient also treated with diuretics.

Perseveration in left spatial neglect: Drawing and cancellation tasks

Perseveration in target cancellation tasks and in drawing by copy and from memory was investigated in 21 right-brain-damaged patients, seven with no evidence of left visuo-spatial neglect, and 14 with neglect. Eight such neglect patients showed perseveration in both cancellation and drawing tasks, although no correlation was found with the severity of neglect. Patients with perseveration were not disproportionately impaired in tasks assessing executive (fluency, Stroop colour–word interference, and Weigl's sorting test), and visuo-spatial short-term memory function. In the context of a two-component hypothesis, graphic perseveration (the first component) is a specific disorder that manifests in a variety of tasks, particularly those requiring serial graphic production. Unilateral spatial neglect (the second component) may trigger and facilitate the production of perseveration errors, with a contra-ipsilateral gradient of increasing severity.

Are drawing perseverations part of the neglect syndrome?

Unilateral neglect patients typically omit to cancel contralesional targets. Moreover, they can repeatedly cancel ipsilesional stimuli exhibiting what is termed ‘perseverative behavior’. Two alternative accounts of this behavior have been proposed. According to one of them, it is considered as integral to neglect and due either to a perceptual (allochiria), or a premotor (directional hypokinesia) pathological mechanism leading to the ipsilesional displacement of contralesional responses. According to the other one, perseverations are interpreted as the consequence of motor–control–disinhibition co-occurring with, although independent of, spatial neglect. We compared some crucial predictions of these two hypotheses on a group of 10 right-brain-damaged patients, eight with neglect and two without neglect, showing a perseverative behavior in both conventional and experimental cancellation tasks. In our experiment, the spatial location and the numerosity of targets were manipulated to obtain different degrees of horizontal alignment between targets on the left and on the right of the central vertical axis of the sheet. We found that ipsilesional perseverations were not influenced by left neglected targets and were not correlated to neglect severity. Additionally, perseverative errors were associated with right basal ganglia lesions rather than with presence of neglect. These findings support the view that two different pathological mechanisms might be involved in left spatial neglect and ipsilesional perseverative behavior.

Translation Research for the Rehabilitation of Left Spatial Neglect and Associated Disorders of Attention in Stroke Patients

Abstract The syndrome of unilateral neglect, typified by a lateralized attention bias and neglect of contralateral space, is an important cause of morbidity and disability after a stroke. In this review, we discuss the challenges that face researchers attempting to elucidate the mechanisms and effectiveness of rehabilitation treatments. The neglect syndrome is a heterogeneous disorder, and it is not clear which of its symptoms cause ongoing disability. We review current methods of neglect assessment and propose logical approaches to selecting treatments, while acknowledging that further study is still needed before some of these approaches can be translated into routine clinical use. We conclude with systems-level suggestions for hypothesis development that would hopefully form a sound theoretical basis for future approaches to the assessment and treatment of neglect.

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

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

Effects of emotional and non-emotional cues on visual search in neglect patients: Evidence for distinct sources of attentional guidance

In normal observers, visual search is facilitated for targets with salient attributes. We compared how two different types of cue (expression and colour) may influence search for face targets, in healthy subjects (n=27) and right brain-damaged patients with left spatial neglect (n=13). The target faces were defined by their identity (singleton among a crowd of neutral faces) but could either be neutral (like other faces), or have a different emotional expression (fearful or happy), or a different colour (red-tinted). Healthy subjects were the fastest for detecting the colour-cued targets, but also showed a significant facilitation for emotionally cued targets, relative to neutral faces differing from other distracter faces by identity only. Healthy subjects were also faster overall for target faces located on the left, as compared to the right side of the display. In contrast, neglect patients were slower to detect targets on the left (contralesional) relative to the right (ipsilesional) side. However, they showed the same pattern of cueing effects as healthy subjects on both sides of space; while their best performance was also found for faces cued by colour, they showed a significant advantage for faces cued by expression, relative to the neutral condition. These results indicate that despite impaired attention towards the left hemispace, neglect patients may still show an intact influence of both low-level colour cues and emotional expression cues on attention, suggesting that neural mechanisms responsible for these effects are partly separate from fronto-parietal brain systems controlling spatial attention during search.

The effects of time-on-task and concurrent cognitive load on normal visuospatial bias.

Research suggests that the severity of left spatial neglect can be modulated by changes in general alertness. Analogous effects in healthy volunteers now suggest that this may reflect an amplified form of a normal pattern. Recent neuropsychological studies also suggest that concurrent cognitive load may exacerbate rightward bias. In this study, for the first time, the authors examined the effect of both factors on spatial bias in healthy volunteers. Participants performed a task in which as many letters as possible needed to be reported from a briefly presented visual array under three conditions (alone, with a syllable-discrimination secondary task and with a pitch-discrimination secondary task). The results confirmed a significant rightward shift associated with time-on-task across all conditions--the first demonstration of such an effect within a fixation controlled, brief presentation task. While the secondary tasks influenced overall visual performance, there was no discernable effect on bias.

Semantic processing of neglected numbers

While neglected stimuli can still be processed, few studies have directly addressed the issue of the unconscious access to semantics. In order to clarify this issue, we engaged four patients with unilateral left spatial neglect in a number comparison task. Each target number was preceded by a lateralized number prime, either in the intact or neglected hemifield (HF). Both group analyses and the intensive study of a single patient show that left (neglected) as well as right (consciously perceived) number primes affect performance: primes representing quantities that fall on the same side of the reference as the target lead to faster categorization. This congruency effect is highly suggestive of numerical semantic processing of neglected stimuli. Absence of conscious perception of neglected primes was evaluated using a combination of subjective and objective measures of performance in forced-choice tasks.