Unilateral Neglect Research Articles

Streams of conscious visual experience

Consciousness, a cornerstone of human cognition, is believed to arise from complex neural interactions. Traditional views have focused on localized fronto-parietal networks or broader inter-regional dynamics. In our study, we leverage advanced fMRI techniques, including the novel Functionnectome framework, to unravel the intricate relationship between brain circuits and functional activity shaping visual consciousness. Our findings underscore the importance of the superior longitudinal fasciculus within the fronto-parietal fibers, linking conscious perception with spatial neglect. Additionally, our data reveal the critical contribution of the temporo-parietal fibers and the splenium of the corpus callosum in connecting visual information with conscious representation and their verbalization. Central to these networks is the thalamus, posited as a conductor in synchronizing these interactive processes. Contrasting traditional fMRI analyses with the Functionnectome approach, our results emphasize the important explanatory power of interactive mechanisms over localized activations for visual consciousness. This research paves the way for a comprehensive understanding of consciousness, highlighting the complex network of neural connections that lead to awareness.

Quantifying the Use of Space in the Clock Drawing Test: Validity in Hemispatial Neglect.

The Clock Drawing Test (CDT) is a widely used test for cognitive screening as its execution taps into a large number of cognitive functions. Because of the involvement of visuospatial abilities, the CDT is also commonly used to assess hemispatial neglect. In the present study, we introduce a new quantitative scoring method for the CDT that aims to measure the use of space for each half of the clock face and asymmetries of space use. Two measures are introduced: the explored space (ES) and used space (US) for each half of the clock, as well as two derived asymmetry indices. Such new measures were applied to CDTs of four groups of participants: right brain-damaged patients without visuospatial neglect, two groups of right brain-damaged patients with varying degrees of visuospatial neglect, and a group of neurologically healthy participants. Analyses showed that only neglect patients explored and used the left clock half significantly less than the right one. This result was also confirmed by the asymmetry indices, where neglect patients showed a stronger rightward bias. For neglect patients, the US asymmetry index correlated with the patients' scores on the neuropsychological tests. The analyses of receiver operating characteristic curves showed that left US and left ES scores had good accuracy in categorizing neglect patients. The present work provides new quantitative indices of CDT space usage in hemispatial neglect. Cutoffs are provided for clinical practice.

Validation of the interdisciplinary Norwegian vision assessment tool KROSS in stroke patients admitted to hospital or rehabilitation services

IntroductionIdentifying vision problems after stroke is important for providing appropriate referral and vision rehabilitation in healthcare services. In Norway, vision assessment is not a standard routine or integrated in stroke care, due to lack of knowledge, guidelines and validated Norwegian assessment tools for healthcare professionals (HCPs) without formal vision competence. This study aimed to validate and assess the reliability of the KROSS (Competence, Rehabilitation of Sight after Stroke) tool for identifying vision problems in stroke patients.MethodsThe KROSS tool has 21 items, including symptoms, observations, and assessment of visual acuity, visual field, eye movements and visual inattention. The primary outcome is to identify if a vision problem is present. Sixty-seven stroke survivors (69.8 years, 28 females) were assessed twice. The first KROSS assessment was by an HCP without formal vision competence and compared to a reference assessment by an optometrist/KROSS specialist within 2 days. Sensitivity, specificity, positive and negative predictive values (PPV/NPV) and inter-rater reliability (Gwet’s AC1/Cohen’s Kappa) were calculated with 95% confidence intervals.ResultsThe KROSS tool demonstrated high sensitivity (98%) and specificity (83%), with excellent reliability (AC1 > 0.86/Kappa > 0.83) and observer agreement (93%) for the primary outcome. A vision problem was identified in 64% of patients, where 44% reported a vision symptom. The PPV and NPV for identifying a vision problem were 0.91 and 0.95 respectively. Sensitivity scores for visual acuity, reading, and visual inattention assessments were all excellent (> 80%) and specificity scores were high for all items (> 70%). Most items showed excellent or substantial agreement (AC1 > 0.7/kappa > 0.6). The lowest agreements were for motility (AC1 > 0.8/kappa > 0.4) and peripheral visual fields (AC1 > 0.8/kappa > 0.5).ConclusionsThis study shows that the KROSS tool shows promise as a valuable tool for integrating vision assessment into stroke health services. It has high sensitivity and specificity, and excellent reliability, indicating high accuracy for identifying a vision problem. This indicates that the KROSS tool can reliably be used by HCPs without formal vision competence to identify a vision problem. The fact that many stroke survivors were identified with vision problems using the KROSS tool, even if they did not complain of visual symptoms, supports the significance of including structured vision assessment in stroke care.

Diagnosis of spatial neglect and rehabilitation access for stroke survivors.

Spatial neglect in stroke survivors is associated with a decrease in quality of life. This disorder occurs in 20-80% of stroke survivors and up to 1/3 of stroke survivors will continue to experience chronic impairment. Occupational therapists are uniquely qualified to treat stroke survivors with spatial neglect due to their holistic approach but access to therapy is limited. Diagnostic coding is used to help determine appropriate reimbursement and continuation of care including rehabilitation services. The objectives of this study were to 1) identify the prevalence of diagnostic coding for spatial neglect in stroke survivors, and 2) identify the prevalence and types of rehabilitation for patients with diagnostic coding for spatial neglect. We completed a retrospective cohort analysis using 2018 and 2019 5% Medicare Limited Data Sets from the Centers for Medicare and Medicaid Services. We extracted all ischemic stroke survivors and stratified them by the presence of a secondary diagnostic code indicating spatial neglect. Rehabilitation Current Procedural Terminology codes were used to identify stroke survivors who received rehabilitation. Despite recommendations from clinical practice, only 4.9% had a diagnostic code for spatial neglect. Of those formally diagnosed, only 2.3% received outpatient occupational therapy after being discharged from acute care.

A prospective multi-center study quantifying visual inattention in delirium using generative models of the visual processing stream

The visual attentional deficits in delirium are poorly characterized. Studies have highlighted neuro-anatomical abnormalities in the visual processing stream but fail at quantifying these abnormalities at a functional level. To identify these deficits, we undertook a multi-center eye-tracking study where we recorded 210 sessions from 42 patients using a novel eye-tracking system that was made specifically for free-viewing in the (ICU); each session lasted 10 min and was labeled with the delirium status of the patient using the Confusion Assessment Method in ICU (CAM-ICU). To analyze this data, we formulate the task of visual attention as a hierarchical generative process that yields a probabilistic distribution of the location of the next fixation. This distribution can then be compared to the measured patient fixation producing a correctness score which is tallied compared across delirium status. This analysis demonstrated that the visual processing system of patients suffering from delirium is functionally restricted to a statistically significant degree. This is the first study to explore the potential mechanisms underpinning visual inattention in delirium and suggests a new target of future research into a disease process that affects one in four hospitalized patients with severe short and long-term consequences.

The engagement of temporal attention in left spatial neglect

Previous literature showed how left spatial neglect arises from an asymmetrical distribution of spatial attention. However, it was also suggested that left spatial neglect might be partially caused or at least worsened by non-spatial attention disorders of the right-lateralized stimulus-driven attentional fronto-parietal network. Here, we psychophysically tested the efficiency of temporal attentional engagement of foveal perception through meta-contrast (Experiment 1) and “attentional” masking (Experiment 2) tasks in patients with right-hemisphere stroke with left neglect (N+), without left neglect (N-) and matched healthy controls (C). In both experiments, N+ patients showed higher thresholds, not only than Cs, but also than N- patients. Temporal engagement was clinically impaired in all N+ patients and highly correlated with their typical inability to direct spatial attention towards stimuli on the left side. Our findings suggest that a temporal impairment of attentional engagement is a relevant deficit of left spatial neglect.

Gaze and attention: mechanisms underlying the therapeutic effect of optokinetic stimulation in spatial neglect

Left smooth pursuit eye movement training in response to large-field visual motion (optokinetic stimulation) has become a promising rehabilitation method in left spatial inattention or neglect. The mechanisms underlying the therapeutic effect, however, remain unknown. During optokinetic stimulation, there is an error in visual localization ahead of the line of sight. This could indicate a change in the brain’s estimate of one’s own direction of gaze. We hypothesized that optokinetic stimulation changes the brain’s estimate of gaze. Because this estimate is critical for coding the locus of attention in the visual space relative to the body and across sensory modalities, its change might underlie the change in spatial attention. Here, we report that in healthy participants optokinetic stimulation causes not only a directional bias in the proprioceptive signal from the extraocular muscles, but also a corresponding shift of the locus of attention. Both changes outlasted the period of stimulation. This result forms a step in investigating a causal link between the adaptation in the sensorimotor gaze signals and the recovery in spatial neglect.

Implicit Selective Attention: The Role of the Mesencephalic-basal Ganglia System.

The ability of the brain to recognize and orient attention to relevant stimuli appearing in the visual field is highlighted by a tuning process, which involves modulating the early visual system by both cortical and subcortical brain areas. Selective attention is coordinated not only by the output of stimulus-based saliency maps but is also influenced by top-down cognitive factors, such as internal states, goals, or previous experiences. The basal ganglia system plays a key role in implicitly modulating the underlying mechanisms of selective attention, favouring the formation and maintenance of implicit sensory-motor memories that are capable of automatically modifying the output of priority maps in sensory-motor structures of the midbrain, such as the superior colliculus. The article presents an overview of the recent literature outlining the crucial contribution of several subcortical structures to the processing of different sources of salient stimuli. In detail, we will focus on how the mesencephalic- basal ganglia closed loops contribute to implicitly addressing and modulating selective attention to prioritized stimuli. We conclude by discussing implicit behavioural responses observed in clinical populations in which awareness is compromised at some level. Implicit (emergent) awareness in clinical conditions that can be accompanied by manifest anosognosic symptomatology (i.e., hemiplegia) or involving abnormal conscious processing of visual information (i.e., unilateral spatial neglect and blindsight) represents interesting neurocognitive "test cases" for inferences about mesencephalicbasal ganglia closed-loops involvement in the formation of implicit sensory-motor memories.

Enhancing poststroke hand movement recovery: Efficacy of RehabSwift, a personalized brain-computer interface system.

This study explores the efficacy of our novel and personalized brain-computer interface (BCI) therapy, in enhancing hand movement recovery among stroke survivors. Stroke often results in impaired motor function, posing significant challenges in daily activities and leading to considerable societal and economic burdens. Traditional physical and occupational therapies have shown limitations in facilitating satisfactory recovery for many patients. In response, our study investigates the potential of motor imagery-based BCIs (MI-BCIs) as an alternative intervention. In this study, MI-BCIs translate imagined hand movements into actions using a combination of scalp-recorded electrical brain activity and signal processing algorithms. Our prior research on MI-BCIs, which emphasizes the benefits of proprioceptive feedback over traditional visual feedback and the importance of customizing the delay between brain activation and passive hand movement, led to the development of RehabSwift therapy. In this study, we recruited 12 chronic-stage stroke survivors to assess the effectiveness of our solution. The primary outcome measure was the Fugl-Meyer upper extremity (FMA-UE) assessment, complemented by secondary measures including the action research arm test, reaction time, unilateral neglect, spasticity, grip and pinch strength, goal attainment scale, and FMA-UE sensation. Our findings indicate a remarkable improvement in hand movement and a clinically significant reduction in poststroke arm and hand impairment following 18 sessions of neurofeedback training. The effects persisted for at least 4 weeks posttreatment. These results underscore the potential of MI-BCIs, particularly our solution, as a prospective tool in stroke rehabilitation, offering a personalized and adaptable approach to neurofeedback training.

The Contestation of Islamic Boarding School Womens's View of Wifes' Rights in Poligamy

This study examines the contention around Islamic boarding school women's view of wives' rights in polygamous marriages. It aims to answer academic questions, specifically how and why there is contention among Islamic boarding school women over the rights of wives in polygamy. Furthermore, it also aims to answer what consequences this contestation has for the practice of polygamy, which is common in Islamic boarding schools. This paper is an empirical research that takes a sociological perspective. The analysis is based on Pierre Bourdieu's Cultural Sociology theory. Data were gathered through an interview study with research subjects from five traditional Islamic boarding schools in Lampung Province. The findings of this study show that the contestation of wives' rights in polygamy is influenced by the level of understanding of religious texts and norms, social and economic realities, and the strength of the patriarchal traditions and systems that surround it. Most women are denied the opportunity to fight for their bodily and spiritual rights, both before and after polygamous marriage occurs. Women in Islamic boarding schools recognize that men's supremacy influences the neglect of women's rights in polygamy because their understanding of religious texts is conservative. Women have no bargaining power when their husbands seek to practice polygamy. Conservatives believe that polygamy is a fate and consequence that women who want to marry a caregiver or an Islamic boarding school leader (Kyai) must accept. A moderate perspective necessitates that polygamy be practiced with proportional rights between husband and wife. The repercussions of this contestation have resulted in a better appreciation of the importance of men's and women's rights being proportionate, as well as mutual protection.

The disengagement deficit after right-hemisphere damage: Distinct roles of lateral frontal and parietal damage

An influential model of spatial attention postulates three main attention-orienting mechanisms: disengagement, shifting, and engagement. Early research linked disengagement deficits with superior parietal damage, regardless of hemisphere or presence of spatial neglect. Subsequent studies supported the involvement of more ventral parietal regions, especially in the right hemisphere, and linked spatial neglect to deficient disengagement from ipsilateral cues. However, previous lesion studies faced serious limitations, such as small sample sizes and the lack of brain-injured controls without neglect. Additionally, some studies employed symbolic cues or used long cue-target intervals, which may fail to reveal impaired disengagement. We here used a machine-learning approach to conduct lesion-symptom mapping (LSM) on 89 patients with focal cerebral lesions to the left (LH) or right (RH) cerebral hemisphere. A group of 54 healthy participants served as controls. The paradigm used to uncover disengagement deficits employed non-predictive cues presented in the visual periphery and at short cue-target intervals, targeting exogenous attention. The main factors of interest were group (healthy participants, LH, RH), target position (left, right hemifield) and cue validity (valid, invalid). LSM-analyses were performed on two indices: the validity effect, computed as the absolute difference between reaction times (RTs) following invalid compared to valid cues, and the disengagement deficit, determined by the difference between contralesional and ipsilesional validity effects. While LH patients showed general slowing of RTs to contralesional targets, only RH patients exhibited a disengagement deficit from ipsilesional cues. LSM associated the validity effect with a right lateral frontal cluster, which additionally affected subcortical white matter of the right arcuate fasciculus, the corticothalamic pathway, and the superior longitudinal fasciculus. In contrast, the disengagement deficit was related to damage involving the right temporoparietal junction. Thus, our results support the crucial role of right inferior parietal and posterior temporal regions for attentional disengagement, but also emphasize the importance of lateral frontal regions, for the reorienting of attention.

Dorsal pulvinar inactivation leads to spatial selection bias without perceptual deficit

The dorsal pulvinar has been implicated in visuospatial attentional and perceptual confidence processing. Pulvinar lesions in humans and monkeys lead to spatial neglect symptoms, including an overt spatial saccade bias during free choices. However, it remains unclear whether disrupting the dorsal pulvinar during target selection that relies on a perceptual decision leads to a perceptual impairment or a more general spatial orienting and choice deficit. To address this question, we reversibly inactivated the unilateral dorsal pulvinar by injecting GABA-A agonist THIP while two macaque monkeys performed a color discrimination saccade task with varying perceptual difficulty. We used Signal Detection Theory and simulations to dissociate perceptual sensitivity (d-prime) and spatial selection bias (response criterion) effects. We expected a decrease in d-prime if dorsal pulvinar affects perceptual discrimination and a shift in response criterion if dorsal pulvinar is mainly involved in spatial orienting. After the inactivation, we observed response criterion shifts away from contralesional stimuli, especially when two competing stimuli in opposite hemifields were present. Notably, the d-prime and overall accuracy remained largely unaffected. Our results underline the critical contribution of the dorsal pulvinar to spatial orienting and action selection while showing it to be less important for visual perceptual discrimination.

Sustained bias of spatial attention in a 3 T MRI scanner

When lying inside a MRI scanner and even in the absence of any motion, the static magnetic field of MRI scanners induces a magneto-hydrodynamic stimulation of subjects’ vestibular organ (MVS). MVS thereby not only causes a horizontal vestibular nystagmus but also induces a horizontal bias in spatial attention. In this study, we aimed to determine the time course of MVS-induced biases in both VOR and spatial attention inside a 3 T MRI-scanner as well as their respective aftereffects after participants left the scanner. Eye movements and overt spatial attention in a visual search task were assessed in healthy volunteers before, during, and after a one-hour MVS period. All participants exhibited a VOR inside the scanner, which declined over time but never vanished completely. Importantly, there was also an MVS-induced horizontal bias in spatial attention and exploration, which persisted throughout the entire hour within the scanner. Upon exiting the scanner, we observed aftereffects in the opposite direction manifested in both the VOR and in spatial attention, which were statistically no longer detectable after 7 min. Sustained MVS effects on spatial attention have important implications for the design and interpretation of fMRI-studies and for the development of therapeutic interventions counteracting spatial neglect.

Rehabilitation for Unilateral Spatial Neglect

Unilateral spatial neglect (USN) is a symptom of unilateral brain damage resulting in failure to report sensory phenomena in the contra-lesional space. It is associated with motor impairment as well as sensory deficits. Recent research suggests that USN, may be caused by a disruption in the interhemispheric balance of the visual attention network. Based on this hypothesis, non-invasive brain stimulation (NIBS), such as repetitive transcranial magnetic stimulation (rTMS) and transcranial direct current stimulation (tDCS), is utilized in the rehabilitation of USN patients. Presently, inhibitory stimulation by continuous theta burst stimulation (cTBS) on contra-lesional parietal cortex are believed to be the most promising method. Conversely, compensation by attentional network of the non-lesioned hemisphere plays an important role in the recovery of USN. Recent imaging studies revealed that functional and structural connectivity of attentional networks within a lesioned hemisphere and between lesioned and non-lesioned hemispheres affects spontaneous recovery and effectiveness of rehabilitation approach such as prism adaptation therapy. These findings are useful in elucidating the pathophysiology of USN and predicting functional outcome. Furthermore, we hope that understanding the pathophysiology will enable the development of new rehabilitation strategies and appropriate treatment selection.

Unilteral Spatial Neglect: Clinical Manifestations and Neural Correlates

Unilateral spatial neglect is the failure of brain-damaged patients to report, respond, or orient to novel or meaningful stimuli presented to the contralateral side of the lesion. This usually involves the right cerebral hemisphere. Neglect presents with no restriction in gaze direction and results in difficulty across various aspects of daily activities, distinguishing it from simple homonymous hemianopia. The basic mechanisms underlying neglect is rightward bias of spatial attention, while non-direction-specific cognitive problems may contribute to clinical expressions of neglect.

Neural Mechanisms of Attention

Classical evidence for neural mechanisms of attention resulted from findings that attention to sensory signals modulated sensory neuronal responses in both humans and non-human animals. These findings led scientists to propose a variety of sophisticated information-processing and mathematical models of attention. Recent advances in neuroimaging and studies including hemispatial neglect and attention deficits in patients have also facilitated understanding of neural mechanisms of attention in terms of functional specialization and large-scale brain network. Here, we reviewed neural mechanisms of attention from classical literature up to recent advances.

The Effect of Ward-Based Unilateral neglect Intervention Program on the Daily Life Function of Stroke Patients

The Effect of Ward-Based Unilateral neglect Intervention Program on the Daily Life Function of Stroke Patients

The Illusion of Papuan Independence through Benny Wenda’s Transnational Advocacy Network Strategy during the #FreeWestPapua Campaign in 2020

This research reveals critically rather than using images of modern development and progress on Indigenous Papuans (OAP) who are often demanded to engage in social change by ignoring one's identity. The accumulation of OAP disillusionment that began in the history of the Act of Free Choice continued with the neglect of cultural rights as a reflection of the collective dignity that is still running. This triggered some OAP segments who called themselves independent Papuan groups to choose to garner international support in efforts to secede principles. As done by Benny Wenda as OAP through international forums to encourage the fulfillment of political rights caused by the closed access to the Papuan people's movement in fighting for the issue of Free Papua. He described the resistance of Papuan identity to expand the target domain of its supporter audience. Sporadically through the use of international civil society networks, the authors highlight the advocacy strategies undertaken Transnational Advocacy Network (TAN) through the #PapuanLivesMatter campaign that raised the existence of Benny Wenda in representing Free Papua in the midst of fragmentation that occurred. So the research questions in this study are: What is Benny Wenda's strategy in representing an independent Papua in the midst of fragmentation of separatist groups in Papua? The method for accessing the variables in the theory will be traced based on historical methods that are explained qualitatively.

Virtual reality as a method of cognitive training of processing speed, working memory, and sustained attention in persons with acquired brain injury: a protocol for a randomized controlled trial.

Acquired brain injury (ABI) often leads to persisting somatic, cognitive, and social impairments. Cognitive impairments of processing speed, sustained attention, and working memory are frequently reported and may negatively affect activities of daily living and quality of life. Rehabilitation efforts aiming to retrain these cognitive functions have often consisted of computerized training programs. However, few studies have demonstrated effects that transfer beyond the trained tasks. There is a growing optimism regarding the potential usefulness of virtual reality (VR) in cognitive rehabilitation. The research literature is sparse, and existing studies are characterized by considerable methodological weaknesses. There is also a lack of knowledge about the acceptance and tolerability of VR as an intervention method for people with ABI. The present study aims to investigate whether playing a commercially available VR game is effective in training cognitive functions after ABI and to explore if the possible effects transfer into everyday functioning. One hundred participants (18-65years), with a verified ABI, impairments of processing speed/attention, and/or working memory, and a minimum of 12months post injury will be recruited. Participants with severe aphasia, apraxia, visual neglect, epilepsy, and severe mental illness will be excluded. Participants will be randomized into two parallel groups: (1) an intervention group playing a commercial VR game taxing processing speed, working memory, and sustained attention; (2) an active control group receiving psychoeducation regarding compensatory strategies, and general cognitive training tasks such as crossword puzzles or sudoku. The intervention period is 5weeks. The VR group will be asked to train at home for 30min 5days per week. Each participant will be assessed at baseline with neuropsychological tests and questionnaires, after the end of the intervention (5weeks), and 16weeks after baseline. After the end of the intervention period, focus group interviews will be conducted with 10 of the participants in the intervention group, in order to investigate acceptance and tolerability of VR as a training method. This study will contribute to improve understanding of how VR is tolerated and experienced by the ABI population. If proven effective, the study can contribute to new rehabilitation methods that persons with ABI can utilize in a home setting, after the post-acute rehabilitation has ended.

Super-selective injection of propofol into the intracranial arteries enables Patient's self-evaluation of expected neurological deficit

IntroductionIt is hard to realize the extent of the expected postoperative neurological deficit for patients themselves. The provision of appropriate information can contribute not only to examining surgical indications but also to filling the gap between patient and expert expectations. We hypothesized that propofol infusion into the intracranial arteries (ssWada) could induce focal neurological symptoms with preserved wakefulness, enabling the patients to evaluate the postsurgical risk subjectively. MethodsPresurgical evaluation using ssWada was performed in 28 patients with drug-resistant epilepsy. Based on anatomical knowledge, propofol was super-selectively infused into the intracranial arteries including the M1, M2, and M3 segments of the middle cerebral artery (MCA), A2 segment of the anterior cerebral artery, and P2 segment of the posterior cerebral artery to evaluate the neurological and cognitive symptoms. We retrospectively analyzed a total of 107 infusion trials, including their target vessels, and elicited symptoms of motor weakness, sensory disturbance, language, unilateral hemispatial neglect (UHN), and hemianopsia. We evaluated preserved wakefulness which enabled subjective evaluations of the symptoms and comparison of the subjective experience to the objective findings, besides adverse effects during the procedure. ResultsPreserved wakefulness was found in 97.2% of all trials. Changes in neurological symptoms were positively evaluated for motor weakness in 51.4%, sensory disturbance in 5.6%, language in 48.6%, UHN in 22.4%, and hemianopsia in 32.7%. Six trials elicited seizures. Multivariate analysis showed significant correlations between symptom and infusion site of language and left side, language and MCA branches, motor weakness and A2 or M2 superior division, and hemianopsia and P2. Transient adverse effect was observed in 8 cases with 12 infusion trials (11.2 %). ConclusionThe ssWada could elicit focal neurological symptoms with preserved wakefulness. The methodology enables specific evaluation of risk for cortical resection and subjective evaluation of the expected outcome by the patients.