Right spatial neglect after left hemisphere stroke: qualitative and quantitative study

Underdiagnosis of Unilateral Spatial Neglect in stroke unit

OBJECTIVES

Unilateral spatial neglect (USN) is the incapacity to respond to stimuli presented opposite to a dysfunctional cerebral hemisphere. It is usually caused by non-dominant hemisphere lesions, leads to poorer prognosis and might be underdiagnosed. The objectives of the study were to ascertain the presence of USN in acute stroke patients and analyze the possible degree of underdiagnosis in a Stroke Unit.

MATERIALS AND METHODS

Prospective study of consecutive non-dominant hemisphere stroke patients within a period of 21 months. "Line Bisection" and "Triangles Cancellation" tests were used for USN screening and "Circle Gap Detection Task" to confirm the USN. The results were compared with routine Stroke Unit assessment using the NIHSS to determine the possible degree of underdiagnosis.

RESULTS

A total of 62 subjects, 38 women (61.29%), mean age of 74.05 (SD 10.5) years, were included. USN was diagnosed in 25 cases (40.3%) but 56% of them were not detected in routine evaluation using the NIHSS.

CONCLUSIONS

Unilateral spatial neglect, a common cognitive deficit after acute stroke, is greatly underdiagnosed in routine Stroke Unit assessment. The use of simple USN-specific screening tools would improve diagnosis and therefore the possibility of implementing appropriate rehabilitation strategies.

Conventional and functional assessment of spatial neglect: Clinical practice suggestions

OBJECTIVE

Spatial neglect (SN) constitutes a substantial barrier to functional recovery after acquired brain injury. However, because of its multimodal nature, no single test can capture all the signs of SN. To provide a clinically feasible solution, we used conventional neuropsychological tests as well as the Catherine Bergego Scale (CBS) via the Kessler Foundation Neglect Assessment Process (KF-NAP). The goal was to add evidence that a global approach should detect better even subtle signs of SN.

METHOD

Fourteen individuals with lesions located in the right cerebral hemisphere participated in the study. Participants were assessed with a comprehensive battery of neuropsychological tests, comprising a set of visuospatial tests to evaluate several spatial domains. In addition, patients underwent functional assessment with the Barthel Index, the Functional Independence Measure (FIM), and the CBS via KF-NAP.

RESULTS

The CBS via KF-NAP was associated with the visuospatial paper-based tests (p = .004) as well as the Motor FIM (p = .003), and was more sensitive than the Behavioral Inattention Test-Conventional in detecting SN (p = .014).

CONCLUSIONS

We showed that the CBS via KF-NAP was able: (a) to detect functional impairment, especially motor, related to SN; (b) to selectively measures spatial rather than nonspatial dysfunctions; and (c) to be highly sensitive in detecting SN signs especially in those patients with mild severity, covering several aspects of SN manifestations. The patient's SN diagnosis based on the CBS via KF-NAP is clinically important and directly relevant to care planning and goal setting. (PsycINFO Database Record (c) 2018 APA, all rights reserved).

High-speed widefield photoacoustic microscopy of small-animal hemodynamics

Optical-resolution photoacoustic microscopy (OR-PAM) has become a popular tool in small-animal hemodynamic studies. However, previous OR-PAM techniques variously lacked a high imaging speed and/or a large field of view, impeding the study of highly dynamic physiologic and pathophysiologic processes over a large region of interest. Here we report a high-speed OR-PAM system with an ultra-wide field of view, enabled by an innovative water-immersible hexagon-mirror scanner. By driving the hexagon-mirror scanner with a high-precision DC motor, the new OR-PAM has achieved a cross-sectional frame rate of 900 Hz over a 12-mm scanning range, which is 3900 times faster than our previous motor-scanner-based system and 10 times faster than the MEMS-scanner-based system. Using this hexagon-scanner-based OR-PAM system, we have imaged epinephrine-induced vasoconstriction in the whole mouse ear and vascular reperfusion after ischemic stroke in the mouse cortex in vivo, with a high spatial resolution and high volumetric imaging speed. We expect that the hexagon-scanner-based OR-PAM system will become a powerful tool for small animal imaging where the hemodynamic responses over a large field of view are of interest.

Structure of corona radiata and tapetum fibers in ventricular surgery

In this study the three-dimensional anatomy of the corona radiata and tapetum via the fiber dissection and diffusion tensor imaging of the brain for ventricular surgery was demonstrated. Ten formalin-fixed cerebral hemispheres were dissected for corona radiata and tapetum via Klingler's fiber dissection method under an operating microscope. The corona radiata and tapetum were dissected through lateral and medial surfaces of the cerebral hemisphere, respectively. All surgical routes for ventricular lesions were evaluated for white matter fibers during and after dissections. Corona radiata and tapetum fibers were demonstrated by dissecting hemispheres through lateral and medial aspects of the brain. The internal capsule contains all fibers that extend from thalamus to cortex and cortex to thalamus, brainstem, and spinal cord. These fan-shaped fibers extending from cortex to internal capsule were named the corona radiata. The corona radiata is not a specific pathway, and it is composed of several different fiber pathways. The tapetum contains splenium and body fibers of the corpus callosum. Tapetum is located immediately medial to the ependymal line of the ventricular wall and forms a fiber layer in the medial optical radiation on the coronal and axial sections. Surgical planning for ventricular lesions requires detailed information regarding white matter fibers that can be obtained by the fiber dissection and diffusion tensor imaging of the brain to decrease surgical complications.

Adaptation to Leftward Shifting Prisms Alters Motor Interhemispheric Inhibition

Adaptation to rightward shifting prisms (rightward prism adaptation, RPA) ameliorates neglect symptoms in patients while adaptation to leftward shifting prisms (leftward prism adaptation, LPA) induces neglect-like behaviors in healthy subjects. It has been hypothesized that prism adaptation (PA) modulates interhemispheric balance between the parietal cortices by inhibiting the posterior parietal cortex (PPC) contralateral to the prismatic deviation, but PA's effects on interhemispheric inhibition (IHI) have not been directly investigated. Since there are hyper-excitable connections between the PPC and primary motor cortex (M1) in the left hemisphere of neglect patients, we reasoned that LPA might mimic right hemisphere lesions by reducing parietal IHI, hyper-exciting the left PPC and PPC-M1 connections, and in turn altering IHI at the motor level. Namely, we hypothesized that LPA would increase IHI from the left to the right M1. We examined changes in left-to-right and right-to-left IHI between the 2 M1s using the ipsilateral silent period (iSP) (Meyer et al. 1995) before and after either LPA or RPA. The iSP was significantly longer after LPA but only from left-to-right and it did not change at all after RPA. This is the first physiological demonstration that LPA alters IHI in the healthy brain.

The Mobility Assessment Course for the Diagnosis of Spatial Neglect: Taking a Step Forward?

Spatial neglect after stroke can be a challenging syndrome to diagnose under standard neuropsychological assessment. There is now sufficient evidence that those affected might demonstrate neglect behavior in everyday settings despite showing no signs of neglect during common neglect tasks. This discrepancy is attributed to the simplified and unrealistic nature of common pen and paper based tasks that do not match the demanding, novel, and complex environment of everyday life. As such, increasing task demands under more ecologically valid scenarios has become an important method of increasing test sensitivity. The main aim of the current study was to evaluate the diagnostic utility of the Mobility Assessment Course (MAC), an ecological task, for the assessment of neglect. If neglect becomes more apparent under more challenging task demands the MAC could prove to be more diagnostically accurate at detecting neglect than conventional methods, particularly as the time from initial brain damage increases. Data collected by Guide Dogs of SA/NT were retrospectively analyzed. The Receiver Operating Characteristic (ROC) curve, a measure of sensitivity and specificity, was used to investigate the diagnostic utility of the MAC and a series of paper and pencil tests in 67 right hemisphere stroke survivors. While the MAC proved to be a more sensitive neglect test (74.2%) when compared to the Star Cancellation (43.3%) and Line Bisection (35.7%) tests, this was at the expense of relatively low specificity. As a result, the ROC curve analysis showed no statistically discernable differences between tasks (p > 0.12), or between subacute and chronic groups for individual tasks (p > 0.45). It is concluded that, while the MAC is an ecologically valid alternative for assessing neglect, regarding its diagnostic accuracy, there is currently not enough evidence to suggest that it is a big step forward in comparison to the accuracy of conventional tests.

Do Neglect Assessments Detect Neglect Differently?

OBJECTIVE

We determined whether various assessment tools detect neglect differently by administering a battery of assessments to people with stroke.

METHOD

We conducted a case series study and administered five neglect assessments (paper-and-pencil, functional, virtual reality) to participants poststroke.

RESULTS

Twelve participants (6 men, 6 women) with stroke completed the assessment battery, which required approximately 2 hr to administer (over one to two sessions). All participants demonstrated neglect on three or more assessments. Functional assessments and the virtual reality assessment detected neglect more frequently than the paper-and-pencil assessments. Participants performed differently on the paper-and-pencil assessments and functional assessments.

CONCLUSION

Because neglect is complex, detection may depend largely on the assessment administered.

Assessment of behavioural deficits following ischaemic stroke in the marmoset

Stroke is a common and devastating disease worldwide. Over the last two decades, many therapeutic approaches to ameliorate ischaemic stroke have been promising in animal studies but failed when transferred to the clinical situation. One of the possible explanations for these failures is the widespread use of animal models of cerebral ischemia that do not mimic the pathology encountered in the clinic. Accordingly, many expert committees recommended the integration of higher order species such as non-human primates in pre-clinical stroke studies. The common marmoset (Callithrix jacchus), a small New World monkey, start to stand out in the neuroscience field as a good compromise between larger primates and rodents. In this review, we discuss the relevance of the use of the marmoset in stroke studies. We will focus on behavioural tests developed in this species to assess sensorimotor deficits and their recovery during acute and chronic stages of brain ischaemia. The aim of this appraisal is to provide a comprehensive overview of the existing approaches to induce stroke in the marmoset as well as the paradigms for behavioural testing in this species. The data summarized in this review should contribute to the improvement of future stoke studies in the marmoset and accordingly improve the translation of the results from bench to bed.

Leftward Deviation and Asymmetric Speed of Egocentric Judgment between Left and Right Visual Fields

The egocentric reference frame is essential for body orientation and spatial localization of external objects. Recent neuroimaging and lesion studies have revealed that the right hemisphere of humans may play a more dominant role in processing egocentric information than the left hemisphere. However, previous studies of egocentric discrimination mainly focused on assessing the accuracy of egocentric judgment, leaving its timing unexplored. In addition, most previous studies never monitored the subjects' eye position during the experiments, so the influence of eye position on egocentric judgment could not be excluded. In the present study, we systematically assessed the processing of egocentric information in healthy human subjects by measuring the location of their visual subjective straight ahead (SSA) and their manual reaction time (RT) during fixation (monitored by eye tracker). In an egocentric discrimination task, subjects were required to judge the position of a visual cue relative to the subjective mid-sagittal plane and respond as quickly as possible. We found that the SSA of all subjects deviated to the left side of the body mid-sagittal plane. In addition, all subjects but one showed the longest RT at the location closest to the SSA; and in population, the RTs in the left visual field (VF) were longer than that in the right VF. These results might be due to the right hemisphere's dominant role in processing egocentric information, and its more prominent representation of the ipsilateral VF than that of the left hemisphere.

Distinct white matter alterations following severe stroke

Objective:

To distinguish white matter remodeling directly induced by stroke lesion from that evoked by remote network dysfunction, using spatial neglect as a model.

Methods:

We examined 24 visual neglect/extinction patients and 17 control patients combining comprehensive analyses of diffusion tensor metrics and global fiber tracking with neuropsychological testing in the acute (6.3 ± 0.5 days poststroke) and chronic (134 ± 7 days poststroke) stroke phases.

Results:

Compared to stroke controls, patients with spatial neglect/extinction displayed longitudinal white matter alterations with 2 defining signatures: (1) perilesional degenerative changes characterized by congruently reduced fractional anisotropy and increased radial diffusivity (RD), axial diffusivity, and mean diffusivity, all suggestive of direct axonal damage by lesion and therefore nonspecific for impaired attention network and (2) transneuronal changes characterized by an increased RD in contralesional frontoparietal and bilateral occipital connections, suggestive of primary periaxonal involvement; these changes were distinctly related to the degree of unrecovered neglect symptoms in chronic stroke, hence emerging as network-specific alterations.

Conclusions:

The present data show how stroke entails global alterations of lesion-spared network architecture over time. Sufficiently large lesions of widely interconnected association cortex induce distinct, large-scale structural reorganization in domain-specific network connections. Besides their relevance to unrecovered domain-specific symptoms, these effects might also explain mechanisms of domain-general deficits in stroke patients, pointing to potential targets for therapeutic intervention.

Rehabilitation of unilateral neglect: Evidence-based medicine

BACKGROUND

In the last decades, several rehabilitation methods have been developed to improve spatial neglect. These can be classified according to their theoretical basis: (i) enhance awareness of neglect behaviour through a top-down mechanism; (ii) low-level bottom-up sensory stimulation; (iii) modulation of inhibitory processes; (iv) increase arousal.

OBJECTIVE

The purpose of this study was to provide an overview of the evidence on the effectiveness of rehabilitation procedures for unilateral neglect.

METHOD

A systematic search was performed to look for all randomised controlled trials aimed at reducing left spatial neglect that included a functional assessment. In addition, recent review papers and meta-analyses were analysed.

RESULTS

Thirty-seven randomized controlled trials were found (12 bottom-up; 12 top-down; 1 interhemispheric competition; 12 combination of approaches) that included 1027 patients with neglect. Although there are some encouraging results, overall, the level of evidence remains low. Poor methodological quality and small sample sizes are major limitations in many published trials.

CONCLUSION

There is a need for well-conducted, large-scale randomised controlled trials that incorporate blinded assessments, evaluation of the generalization to activities of daily living and long-term follow-up.

Not Just Language: Persisting Lateralized Visuospatial Impairment after Left Hemisphere Stroke

OBJECTIVES

Imbalances in spatial attention are most often associated with right hemisphere brain injury. This report assessed 25 chronic left hemisphere stroke patients for attentional bias.

METHODS

Participants were evaluated with a computerized visual search task and a standardized neuropsychological assessment known as the Behavioral Inattention Test (BITC). Twenty age-matched controls were also tested.

RESULTS

Although little to no attentional impairment was observed on the BITC, the computerized visual search task revealed statistically significant contralesional attentional impairment in the left hemisphere stroke group. Specifically, these participants required 208 ms more viewing time, on average, to reliably detect visual targets on the right side of the display compared to detection on the left side, while controls showed a difference of only 8 ms between the two sides.

CONCLUSIONS

The observation of significant leftward visuospatial bias in this chronic stroke group provides further evidence that the left hemisphere also plays a role in the balance of visual attention across space. These results have implications for left hemisphere patients who are often not screened for visuospatial problems, as well as for theories of visual attention which have primarily emphasized the role of the right hemisphere. (JINS, 2016, 22, 695-704).

Neurobiology of Unilateral Spatial Neglect

Hemispatial neglect is a common and disabling consequence of stroke. Earlier studies aimed to identify a single area of the brain where damage caused neglect and sought a single disrupted process that could account for the symptoms. Recent studies have shifted toward identifying component processes and representations underlying spatial attention required for various tasks and identifying areas of the brain responsible for each component that together constitute the network of regions responsible for neglect. This review focuses on recent insights into the mechanisms of neglect, regions of neural dysfunction that cause disruption of particular components or forms of neglect, and potential means of ameliorating neglect. Converging evidence supporting these insights comes from new imaging modalities in acute stroke, functional imaging, transcranial magnetic stimulation, electrophysiological studies in humans, and single-cell recording studies in nonhuman primates.

Assessing chronic stroke survivors with aphasia sheds light on prevalence of spatial neglect

BACKGROUND

Stroke is a chronic disease. Standardized assessment is essential in order to determine areas for treatment. Individuals with aphasia are often excluded from research, because it is believed that their language impairments may impact their ability to provide informed consent. Thus, right spatial neglect could be under-diagnosed.

OBJECTIVE

This study was developed to (1) determine the frequency of spatial neglect in chronic left-brain stroke survivors with aphasia, (2) determine the clinical utility of an aphasia-friendly consent form, and (3) determine any differences between neglect and no-neglect groups regarding activities of daily living (ADL) performance and community independence.

METHODS

Forty-six people were consented at community center. Three were screen failures secondary to the exclusion criteria. A novel, aphasia-friendly consent form was developed to facilitate participation of individuals with aphasia. This enabled 93% or 40 out of the 43 recruited participants to be included in this study. The Behavioral Inattention Test-conventional and the Catherine Bergego Scale via Kessler Foundation Neglect Assessment Process (CBS via KF-NAP) were utilized to determine neglect. The Life Space Questionnaire was used to determine community mobility and independence. The Barthel Index (BI) was used for objective clarification of performance in ADL.

RESULTS

Successful use of the consent form resulted in determination that five out of 40 (12.5%) met criteria for spatial neglect; (on the CBS via KF-NAP). The neglect group had lower scores on the Life Space, suggesting less community mobility and independence, however, it was not statistically significant (p = 0.16). Differences in BI scores were also not significant (p = .013) but the neglect group did have reduced independence.

CONCLUSIONS

This study demonstrates the need to administer functional neglect assessments in left-brain stroke and to include individuals with aphasia in research.

The white matter tracts of the cerebrum in ventricular surgery and hydrocephalus

OBJECTIVE The relationship of the white matter tracts to the lateral ventricles is important when planning surgical approaches to the ventricles and in understanding the symptoms of hydrocephalus. The authors' aim was to explore the relationship of the white matter tracts of the cerebrum to the lateral ventricles using fiber dissection technique and MR tractography and to discuss these findings in relation to approaches to ventricular lesions. METHODS Forty adult human formalin-fixed cadaveric hemispheres (20 brains) and 3 whole heads were examined using fiber dissection technique. The dissections were performed from lateral to medial, medial to lateral, superior to inferior, and inferior to superior. MR tractography showing the lateral ventricles aided in the understanding of the 3D relationships of the white matter tracts with the lateral ventricles. RESULTS The relationship between the lateral ventricles and the superior longitudinal I, II, and III, arcuate, vertical occipital, middle longitudinal, inferior longitudinal, inferior frontooccipital, uncinate, sledge runner, and lingular amygdaloidal fasciculi; and the anterior commissure fibers, optic radiations, internal capsule, corona radiata, thalamic radiations, cingulum, corpus callosum, fornix, caudate nucleus, thalamus, stria terminalis, and stria medullaris thalami were defined anatomically and radiologically. These fibers and structures have a consistent relationship to the lateral ventricles. CONCLUSIONS Knowledge of the relationship of the white matter tracts of the cerebrum to the lateral ventricles should aid in planning more accurate surgery for lesions within the lateral ventricles.

Fiber Tracts of the Medial and Inferior Surfaces of the Cerebrum

OBJECTIVE

Fiber dissection studies of the cerebrum have focused on the lateral surface. No comparable detailed studies have been done on the medial and inferior surfaces. The object of this study was to examine the fiber tracts, cortical, and subcortical structures of the medial and inferior aspects of the brain important in planning operative approaches along the interhemispheric fissure, parafalcine area, and basal surfaces of the cerebrum.

METHODS

Twenty formalin-fixed human hemispheres (10 brains) were examined by fiber dissection technique under ×6-×40 magnifications.

RESULTS

The superior longitudinal fasciculus I, cingulum, inferior longitudinal fasciculus, uncinate fasciculus, optic radiations, tapetum, and callosal fibers were dissected step by step from medial to lateral, exposing the nucleus accumbens, subthalamic nucleus, red nucleus, and central midline structures (fornix, stria medullaris, and stria terminalis). Finally, the central core structures were dissected from medial to lateral.

CONCLUSIONS

Understanding the fiber network underlying the medial and inferior aspects of the brain is important in surgical planning for approaches along the interhemispheric fissure, parafalcine area, and basal surfaces of the cerebrum.

Spatial neglect in a patient with logopenic progressive aphasia

Spatial neglect and extinction are induced by posterior superior temporal and inferior parietal dysfunction. In patients with logopenic progressive aphasia (LPA) these structures are often degenerated, but there are no reports of these disorders being associated. A 53-year-old man with the signs of LPA revealed right-sided spatial neglect on line bisection and drawing tests as well as multimodal extinction. MRI showed left hemispheric posterior temporoparietal atrophy. Since injury to the core structures for these aphasic and attentional syndromes overlaps, patients with LPA should be screened for spatial neglect and extinction.

Sustained attention training reduces spatial bias in Parkinson's disease: a pilot case series

Individuals with Parkinson's disease (PD) commonly demonstrate lateralized spatial biases, which affect daily functioning. Those with PD with initial motor symptoms on the left body side (LPD) have reduced leftward attention, whereas PD with initial motor symptoms on the right side (RPD) may display reduced rightward attention. We investigated whether a sustained attention training program could help reduce these spatial biases. Four non-demented individuals with PD (2 LPD, 2 RPD) performed a visual search task before and after 1 month of computer training. Before training, all participants showed a significant spatial bias and after training, all participants' spatial bias was eliminated.

Cerebral Asymmetry of fMRI-BOLD Responses to Visual Stimulation

Hemispheric asymmetry of a wide range of functions is a hallmark of the human brain. The visual system has traditionally been thought of as symmetrically distributed in the brain, but a growing body of evidence has challenged this view. Some highly specific visual tasks have been shown to depend on hemispheric specialization. However, the possible lateralization of cerebral responses to a simple checkerboard visual stimulation has not been a focus of previous studies. To investigate this, we performed two sessions of blood-oxygenation level dependent (BOLD) functional magnetic resonance imaging (fMRI) in 54 healthy subjects during stimulation with a black and white checkerboard visual stimulus. While carefully excluding possible non-physiological causes of left-to-right bias, we compared the activation of the left and the right cerebral hemispheres and related this to grey matter volume, handedness, age, gender, ocular dominance, interocular difference in visual acuity, as well as line-bisection performance. We found a general lateralization of cerebral activation towards the right hemisphere of early visual cortical areas and areas of higher-level visual processing, involved in visuospatial attention, especially in top-down (i.e., goal-oriented) attentional processing. This right hemisphere lateralization was partly, but not completely, explained by an increased grey matter volume in the right hemisphere of the early visual areas. Difference in activation of the superior parietal lobule was correlated with subject age, suggesting a shift towards the left hemisphere with increasing age. Our findings suggest a right-hemispheric dominance of these areas, which could lend support to the generally observed leftward visual attentional bias and to the left hemifield advantage for some visual perception tasks.

The hybrid model of attentional control: New insights into hemispheric asymmetries inferred from TMS research

Several competing theories on the mechanisms underlying attentional control have emerged over the years that, despite their substantial differences, all emphasize the importance of hemispheric asymmetries. Transcranial magnetic stimulation (TMS) has proven particularly successful in teasing them apart by selective perturbation of the dorsal and ventral fronto-parietal network. We here critically review the TMS literature and show that hemispheric asymmetries within the dorsal attention network differ between parietal and frontal cortex. Specifically, posterior parietal cortex seems to be characterized by a contralateral bias of each hemisphere and competition between them. In contrast, the right frontal eye field seems to be involved in shifting attention toward both hemifields, whereas left frontal eye field is only involved on shifting attention toward the contralateral hemifield. In the light of presented evidence, we propose to revise the functional-anatomical model originally proposed by Corbetta and Shulman (2011, 2002) and introduce a hybrid model of hemispheric asymmetries in attentional control.

Neglect following stroke: the role of sensory sensitivity in visuo-spatial performance

Both proprioceptive and visual manipulations have led to some improvement of the spatial neglect syndrome. Until now, their effects on visuo-spatial behaviour have never been compared simultaneously. The objective of this study was to determine their influence, as a function of the presence of neglect and the side of the brain damage. 19 stroke patients with right and 14 with left brain damage, without or with neglect; realized the Bells test in 5 conditions: a reference condition and 4 sensory conditions, defined according to the side of application (contralesional vs ipsilesional) and the type of perturbation (visual vs proprioceptive). The visuo-spatial behaviour was analyzed for global and spatial aspects and for individual extreme performances. For the neglect group, the restriction of the visual field to the ipsilesional hemi-field significantly diverted the centre of exploration towards the ipsilesional side compared to all other conditions. The weighting of visual cues from the ipsilesional hemi-field seems to be increased in sensory-motor integration processes in neglect patients. In all the groups, although some improvements in performance did occur with sensory manipulation, they were dependent on the individual, particularly for neglect patients. A same performance can be achieved through the use of different sensory-motor strategies, which are individual-related. It is thus important to consider the sensory sensitivity and the responsiveness of each patient before beginning any sensory therapies.

Anosognosia for hemiparesis after left-sided stroke

In patients with left-sided lesions, anosognosia for hemiparesis (AHP) seems to be a rare phenomenon. It has been discussed whether this rareness might be due to an inevitable bias due to language dysfunction and whether the left hemisphere's role for our self-awareness of motor actions thus is underestimated. By applying functional magnetic resonance imaging (fMRI) we examined whether patients with AHP following a left hemisphere stroke show a regular, left-sided or a reversed, right-sided lateralization of language functions. Only the former observation would argue for an original role of the left hemisphere in self-awareness about limb function. In a consecutive series of 44 acute left-sided stroke patients, only one patient (=2%) was identified showing AHP. In this case, we could verify by using fMRI that lateralization of AHP and spatial neglect on the one hand and of language functions on the other hand were reversed. The present single case observation thus argues against an original role of the left hemisphere in self-awareness about limb function. We discuss the data in the context of previous observations in the literature.

Assessment of neglect dyslexia with functional reading materials

BACKGROUND

Spatial neglect is a neurocognitive disorder that affects perception, representation, and/or motor planning. Neglect dyslexia in spatial neglect after right hemisphere damage may co-occur with, or be dissociated from, other spatial neglect signs. Previous neglect dyslexia research focused on word-level stimuli and reading errors. Using single words for assessment may leave some people with neglect dyslexia undiagnosed, and assessment materials that are closer to texts read in real life may better capture neglect dyslexia.

METHOD

The authors tested reading in 67 right hemisphere stroke survivors with 4 types of text materials: words, phrases, an article, and a menu.

RESULTS

Accuracy on reading the menu and article texts was significantly poorer than reading the words and phrases. The hypothesis that assessment materials with ecological validity such as reading a menu and reading an article may be more challenging than reading single words and phrases was supported.

CONCLUSION

Results suggest that neglect dyslexia assessment after stroke should include text materials comparable to those read in everyday life. Increasing the spatial extent of training materials in future research might also yield better functional generalization after right brain stroke.

Effects of age, sex and arm on the precision of arm position sense-left-arm superiority in healthy right-handers

Position sense is an important proprioceptive ability. Disorders of arm position sense (APS) often occur after unilateral stroke, and are associated with a negative functional outcome. In the present study we assessed horizontal APS by measuring angular deviations from a visually defined target separately for each arm in a large group of healthy subjects. We analyzed the accuracy and instability of horizontal APS as a function of age, sex and arm. Subjects were required to specify verbally the position of their unseen arm on a 0-90° circuit by comparing the current position with the target position indicated by a LED lamp, while the arm was passively moved by the examiner. Eighty-seven healthy subjects participated in the study, ranging from 20 to 77 years, subdivided into three age groups. The results revealed that APS was not a function of age or sex, but was significantly better in the non-dominant (left) arm in absolute errors (AE) but not in constant errors (CE) across all age groups of right-handed healthy subjects. This indicates a right-hemisphere superiority for left APS in right-handers and neatly fits to the more frequent and more severe left-sided body-related deficits in patients with unilateral stroke (i.e. impaired APS in left spatial neglect, somatoparaphrenia) or in individuals with abnormalities of the right cerebral hemisphere. These clinical issues will be discussed.

Patients With Left Spatial Neglect Also Neglect the “Left Side” of Time

Previous research suggests that people construct mental time lines to represent and reason about time. However, is the ability to represent space truly necessary for representing events along a mental time line? Our results are the first to demonstrate that deficits in spatial representation (as a function of left hemispatial neglect) also result in deficits in representing events along the mental time line. Specifically, we show that patients with left hemispatial neglect have difficulty representing events that are associated with the past and, thus, fall to the left on the mental time line. These results demonstrate that representations of space and time share neural underpinnings and that representations of time have specific spatial properties (e.g., a left and a right side). Furthermore, it appears that intact spatial representations are necessary for at least some types of temporal representation.

Spatial attention: differential shifts in pseudoneglect direction with time-on-task and initial bias support the idea of observer subtypes

Asymmetry in human spatial attention has long been documented. In the general population the majority of individuals tend to misbisect horizontal lines to the left of veridical centre. Nonetheless in virtually all previously reported studies on healthy participants, there have been subsets of people displaying rightward biases. In this study, we report differential time-on task effects depending on participants' initial pseudoneglect bias: participants with an initial left bias in a landmark task (in which they had to judge whether a transection mark appeared closer to the right or left end of a line) showed a significant rightward shift over the course of the experimental session, whereas participants with an initial right bias shifted leftwards. We argue that these differences in initial biases as well as the differential shifts with time-on task reflect genuine observer subtypes displaying diverging behavioural patterns. These observer subtypes could be driven by differences in brain organisation and/or lateralisation such as varying anatomical pathway asymmetries (Thiebaut de Schotten et al., 2011).

The Predictive Nature of Pseudoneglect for Visual Neglect: Evidence from Parietal Theta Burst Stimulation

Following parietal damage most patients with visual neglect bisect horizontal lines significantly away from the true centre. Neurologically intact individuals also misbisect lines; a phenomenon referred to as ‘pseudoneglect’. In this study we examined the relationship between neglect and pseudoneglect by testing how patterns of pre-existing visuospatial asymmetry predict asymmetry caused by parietal interference. Twenty-four participants completed line bisection and Landmark tasks before receiving continuous theta burst stimulation to the left or right angular gyrus. Results showed that a pre-existing pattern of left pseudoneglect (i.e. right bias), but not right pseudoneglect, predicts left neglect-like behaviour during line bisection following right parietal cTBS. This correlation is consistent with the view that neglect and pseudoneglect arise via a common or linked neural mechanism.

Fiber pathways connecting cortical areas relevant for spatial orienting and exploration

By implementing a task that closely resembled a clinical test for diagnosing spatial neglect in stroke patients, Himmelbach et al. (: Neuroimage 32:1747-1759) found significantly increased activation during active exploration in those cortical areas in healthy subjects that are known to induce spatial neglect in case of a lesion. The present study investigated whether direct intra-hemispheric cortico-cortical connections could be found between these activated clusters using a probabilistic fiber-tracking approach in 52 healthy subjects. We found that parts of the extreme capsule (EmC) and the middle longitudinal fascicle (MdLF) connected the functional cluster in the prefrontal cortex with the superior temporal cortex and the temporo-parietal junction (TPJ) area in both hemispheres. The activation peak in the TPJ was additionally connected to the inferior frontal cortex by parts of the arcuate fascicle and the superior longitudinal fascicle (SLF II) in the right hemisphere. Our study elucidates the connections constituting the perisylvian network for spatial orienting and attention. Hence, we complement the knowledge from patients suffering from spatial neglect by giving first empirical evidence for the complete postulated network in healthy subjects.

Rehabilitation of spatial neglect

Spatial neglect is a frequent cause of disability associated with high costs and duration of hospital stay, increased family burden, and requirements for skilled chronic care. This condition is disproportionately more frequent with right than left hemispheric injury and it is characterized by perceptual, representational, and behavioral deficits involving or directed towards the left hemispace or the left hemibody. Spatial dysfunction is conceptualized into two major components: the perceptual/representational "where" component that results mainly from injury to posterior brain regions and the premotor/intentional "aiming" component that results mostly from damage to anterior brain regions. Additionally, deficits in arousal, vigilance, affective symptoms, and disorders of emotional communication may compound the clinical manifestations of spatial neglect. Evidence-based sources that evaluate the effectiveness of rehabilitation treatments for neglect are, unfortunately, unable to provide a unified consensus for the efficacy of a given treatment approach. The reasons for this failure are related to internal inconsistencies defining appropriate criteria for treatment success and lack of characterization of neglect mechanisms and considerations of patient characteristics related to treatment failure. In this chapter we advocate the use of visual scanning, limb activation therapy, and "general treatment" because we believe that they are appropriately supported by different sources and they may be useful for experimental trials and standardized clinical care. We advocate an integrative approach that takes advantage of the same rehabilitation strategy or task to treat different perceptual, representational, and premotor components of neglect. A variety of therapies that may be familiar to the rehabilitation team may be useful as long as they are applied in a systematized program and are based on good clinical judgment. Information regarding adjuvant pharmacological therapy is sparse but different agents with aminergic and cholinergic activity may be useful. Medication with sedative, antidopaminergic or anticholinergic properties may interfere with the rehabilitation process and should be avoided.

[Early rehabilitation for neurologic patients]

Rehabilitation improves the functional prognosis of patients after a neurologic lesion, and tendency is to begin rehabilitation as soon as possible. This review focuses on the interest and the feasibility of very early rehabilitation, initiated from critical care units. It is necessary to precisely assess patients' impairments and disabilities in order to define rehabilitation objectives. Valid and simple tools must support this evaluation. Rehabilitation will be directed to preventing decubitus complications and active rehabilitation. The sooner rehabilitation is started; the better functional prognosis seems to be.

Disengagement and inhibition of visual-spatial attention are differently impaired in children with rolandic epilepsy and Panayiotopoulos syndrome

We assessed voluntary orientation and reorientation of visuospatial attention in 313 healthy 6- to 22-year-old participants, 30 children suffering from benign epilepsy with centrotemporal spikes (BECTS) and 13 children with Panayiotopoulos syndrome (PS). The developmental section highlights the late development of reorienting skills. Only children with BECTS-R showed a strong tendency toward a rightward bias in attentional orientation. Additionally, a unilateral deficit of disengagement characterizes the patients with BECTS-R and comorbid ADHD. Right rolandic spikes seem to aggravate subclinical reorienting difficulties. Finally, children with PS failed to diffuse inhibition, except in the nearest area outside the attentional focus. This deficit could be attributed to the typical occipital-to-frontal spreading of the spikes in PS. By showing distinct attentional deficiencies according to the epileptic syndrome and the epileptic focus lateralization in BECTS, the results provide new evidence for alterations of attentional mechanisms by interictal epileptic activity, which probably contribute to learning difficulties.

Brain networks of visuospatial attention and their disruption in visual neglect

Visual neglect is a multi-component syndrome including prominent attentional disorders. Research on the functional mechanisms of neglect is now moving from the description of dissociations in patients' performance to the identification of the possible component deficits and of their interaction with compensatory strategies. In recent years, the dissection of attentional deficits in neglect has progressed in parallel with increasing comprehension of the anatomy and function of large-scale brain networks implicated in attentional processes. This review focuses on the anatomy and putative functions of attentional circuits in the brain, mainly subserved by fronto-parietal networks, with a peculiar although not yet completely elucidated role for the right hemisphere. Recent results are discussed concerning the influence of a non-spatial attentional function, phasic alertness, on conscious perception in normal participants and on conflict resolution in neglect patients. The rapid rate of expansion of our knowledge of these systems raises hopes for the development of effective strategies to improve the functioning of the attentional networks in brain-damaged patients.