Ipsilesional Attentional Bias Research Articles

Spatial Neglect Therapy With the Augmented Reality App “Negami” for Active Exploration Training: A Randomized Controlled Trial on 20 Stroke Patients With Spatial Neglect

ObjectiveTo investigate the efficacy of the augmented reality (AR) app “Negami” as an active exploration training for the treatment of spatial neglect. Improvements of the ipsilesional attention and orientation bias (and resulting contralesional neglect) will be examined in stroke patients with spatial neglect and compared with a control group. DesignRandomized controlled trial with an experimental Negami group, consisting of patients with spatial neglect, and a group of neglect patients receiving standard neglect therapy. SettingThree rehabilitation hospitals. ParticipantsTwenty right hemispheric stroke patients with spatial neglect (N=20). InterventionOver a period of 2 weeks, both groups received 5 training sessions per week (à 25 minutes). Neglect behavior was assessed weekly over a 5-week period, with the Negami therapy group receiving a second follow-up assessment at 1-to-2-month intervals after completion of training. Main Outcome MeasuresLetter Cancellation, Bells Test, Copying Task, Line Bisection Task, and a self-developed “Exploration Test”. ResultsBoth groups improved significantly. While the Negami therapy group improved in 4 of 5 neglect tests used, the standard therapy group improved in only 1 of these tests. We observed significantly better improvement in the Negami group already after the first week of training. This difference was also significant after the end of the training as well as 1 week after the end of training and remained stable 1-2 months after the end of treatment. ConclusionNegami can be used as an effective alternative or addition to current standard neglect therapy, and may even be superior to it.

Combined optokinetic stimulation and cueing-assisted reading therapy to treat hemispatial neglect: A randomized controlled crossover trial.

Hemispatial neglect is a disabling cognitive disorder following stroke and effective therapies are required. To evaluate the effects of combined optokinetic stimulation (OKS) and cueing-assisted reading therapy (READ) on the remission of hemispatial neglect following stroke. Randomized, controlled, two-period, crossover trial conducted at a German neurorehabilitation center. Twenty participants with left neglect following right hemispheric stroke (mean age 66 years (SD 11), mean time since stroke 50 days (SD 33)) finished the trial (12 received OKSREAD first, 8 CONTROL first). The intervention consisted of 15 daily sessions of OKS (20 min) and text reading assisted by a therapist providing cues (20 min). The control treatment was a same-number, same-length neuropsychological treatment not targeting visuospatial attention. Primary outcomes were the change in performance of a customized neuropsychological test battery for neglect (0% worst - 100% best) and a test of neglect-related functional disability (Catherine Bergego Scale, 0 no impairment - 30 severest impairment), assessed before and after each treatment period. Secondary outcomes were performance in the 6 single tests composing the battery (e.g., omissions in text reading, center of cancellation in the Bells test, spatial bias of fixations when freely viewing photographs) and a clinical test of anosognosia. Overall performance in the neglect test battery improved slightly more after OKSREAD than after CONTROL (d=6%; p=0.002). The remission of neglect-related functional disability did not differ between treatments (d=-2; p=0.291). Ipsilesional fixation bias during free viewing was the only secondary outcome that was improved by OKSREAD as compared to CONTROL (d= -2.8°; p=0.005). At the applied intensity, the combined OKSREAD intervention slightly attenuated the ipsilesional attention bias in persons with neglect, but it did not improve neglect-related functional disability, anosognosia, or other neglect symptoms to a clinically meaningful degree. URL: http://www. gov. Unique identifier: NCT04273620.

Gaze-contingent display technology can help to reduce the ipsilesional attention bias in hemispatial neglect following stroke

BackgroundHemispatial neglect results from unilateral brain damage and represents a disabling unawareness for objects in the hemispace opposite the brain lesion (contralesional). The patients’ attentional bias for ipsilesional hemispace represents a hallmark of neglect, which results from an imbalanced attentional priority map in the brain. The aim of this study was to investigate whether gaze-contingent display (GCD) technology, reducing the visual salience of objects in ipsilesional hemispace, is able to rebalance this map and increase awareness and exploration of objects in the neglected contralesional hemispace.MethodsUsing remote eye-tracking, we recorded gaze positions in 19 patients with left hemispatial neglect following right-hemisphere stroke and 22 healthy control subjects, while they were watching static naturalistic scenes. There were two task conditions, free viewing (FV) or goal-directed visual search (VS), and four modification conditions including the unmodified original picture, a purely static modification and two differently strong modifications with an additional gaze-contingent mask (GC-LOW, GC-HIGH), that continuously reduced color saturation and contrast of objects in the right hemispace.ResultsThe patients’ median gaze position (Center of Fixation) in the original pictures was markedly deviated to the right in both tasks (FV: 6.8° ± 0.8; VS: 5.5° ± 0.7), reflecting the neglect-typical ipsilesional attention bias. GC modification significantly reduced this bias in FV (GC-HIGH: d = − 3.2 ± 0.4°; p < 0.001). Furthermore, in FV and VS, GC modification increased the likelihood to start visual exploration in the (neglected) left hemifield by about 20%. This alleviation of the ipsilesional fixation bias was not associated with an improvement in detecting left-side targets, in contrast, the GC mask even decreased and slowed the detection of right-side targets. Subjectively, patients found the intervention pleasant and most of the patients did not notice any modification.ConclusionsGCD technology can be used to positively influence visual exploration patterns in patients with hemispatial neglect. Despite an alleviation of the neglect-related ipsilesional fixation bias, a concomitant functional benefit (improved detection of contralesional targets) was not achieved. Future studies may investigate individualized GCD-based modifications as augmented reality applications during the activities of daily living.

Resting-state EEG topographies: Reliable and sensitive signatures of unilateral spatial neglect.

Theoretical advances in the neurosciences are leading to the development of an increasing number of proposed interventions for the enhancement of functional recovery after brain damage. Integration of these novel approaches in clinical practice depends on the availability of reliable, simple, and sensitive biomarkers of impairment level and extent of recovery, to enable an informed clinical-decision process. However, the neuropsychological tests currently in use do not tap into the complex neural re-organization process that occurs after brain insult and its modulation by treatment. Here we show that topographical analysis of resting-state electroencephalography (rsEEG) patterns using singular value decomposition (SVD) could be used to capture these processes. In two groups of subacute stroke patients, we show reliable detection of deviant neurophysiological patterns over repeated measurement sessions on separate days. These patterns generalized across patients groups. Additionally, they maintained a significant association with ipsilesional attention bias, discriminating patients with spatial neglect of different severity levels. The sensitivity and reliability of these rsEEG topographical analyses support their use as a tool for monitoring natural and treatment-induced recovery in the rehabilitation process.

Brain Activations During Optokinetic Stimulation in Acute Right-Hemisphere Stroke Patients and Hemispatial Neglect: An fMRI Study

Objective. Leftward optokinetic stimulation (OKS) is a promising therapeutic approach for right-hemisphere stroke patients with left hemispatial neglect. We questioned whether the putative neural basis is an activation of frontoparietal brain regions involved in the control of eye movements and spatial attention. Methods. We used functional magnetic resonance imaging to investigate brain activations during OKS in acute right-hemisphere stroke patients (RHS, n = 19) compared with healthy control subjects (HC, n = 9). Based on neuropsychological testing we determined the ipsilesional attention bias in all RHS patients, 11 showed manifest hemispatial neglect. Results. In HC subjects, OKS in either direction led to bilateral activation of the visual cortex (V1-V4), frontal (FEF) and supplementary (SEF) eye fields, intraparietal sulcus (IPS), basal ganglia, and thalamus. RHS patients’ activations were generally reduced compared with HC. Nevertheless, leftward OKS bilaterally activated the visual cortex (V1-V4), FEF, SEF, IPS, and thalamus. The neural response to OKS was negatively correlated with patients’ behavioral impairment: The greater the individual attention bias/neglect the weaker the brain activations. Conclusion. In RHS patients, leftward OKS activates frontoparietal regions (FEF, IPS) that are spared from structural brain damage and functionally involved in both oculomotor control and spatial attention. This may provide a neural basis for the known therapeutic effects of OKS on hemispatial neglect. In acute stroke stages, reduced activation levels correlating with neglect severity indicate functional downregulation of the underlying dorsal attention network. Therefore, chronic RHS patients with less severe neglect after recovery of network disturbances may be more suitable candidates for OKS rehabilitation.

"The ipsilesional attention bias in right-hemisphere stroke patients as revealed by a realistic visual search task: Neuroanatomical correlates and functional relevance": Correction to Machner et al. (2018).

A realistic visual search task is introduced, in which eye movements are recorded while the patient searches for paperclips among different everyday objects on a computer display. The "desk task" performance of 34 acute right-hemisphere stroke patients was compared to established paper-pencil tests for neglect and the Posner reaction time task, and finally correlated to structural brain lesions. Most of the patients, even those without clinical neglect signs and with normal paper-pencil test performance, exhibited a clear ipsilesional attention bias in the desk task. This bias was highly correlated to the left-right asymmetry in the Posner task and to neglect-related functional impairment scores. Lesion-symptom mapping revealed task-specific differences: deficits in the desk task were associated with lesions of the superior temporal gyrus, contralesional unawareness in the Posner task with ventral frontal cortex lesions and paper-pencil cancellation bias with damage to the inferior parietal lobe. Neglect behavior was further associated with distinct frontoparietal white matter tract disconnections (inferior longitudinal fasciculus, superior longitudinal fasciculus, arcuate). Results from the novel desk task indicate a functional relevance of spatial attention deficits in right-hemisphere stroke patients, even if they are "subclinical." This should be considered especially in patients without obvious clinical neglect signs. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

The ipsilesional attention bias in right-hemisphere stroke patients as revealed by a realistic visual search task: Neuroanatomical correlates and functional relevance.

Objective: Right-hemisphere stroke may cause an ipsilesional attention bias and left hemispatial neglect. Computerized time-limited tasks are more sensitive than conventional paper–pencil tests in detecting these spatial attention deficits. However, their frequency in the acute stage of stroke, the neuroanatomical basis and functional relevance for patients’ everyday life are unclear. Method: A realistic visual search task is introduced, in which eye movements are recorded while the patient searches for paperclips among different everyday objects on a computer display. The “desk task” performance of 34 acute right-hemisphere stroke patients was compared to established paper–pencil tests for neglect and the Posner reaction time task, and finally correlated to structural brain lesions. Results: Most of the patients, even those without clinical neglect signs and with normal paper–pencil test performance, exhibited a clear ipsilesional attention bias in the desk task. This bias was highly correlated to the left-right asymmetry in the Posner task and to neglect-related functional impairment scores. Lesion-symptom mapping revealed task-specific differences: deficits in the desk task were associated with lesions of the superior temporal gyrus, contralesional unawareness in the Posner task with ventral frontal cortex lesions and paper–pencil cancellation bias with damage to the inferior parietal lobe. Neglect behavior was further associated with distinct frontoparietal white matter tract disconnections (inferior longitudinal fasciculus, superior longitudinal fasciculus, arcuate). Conclusions: Results from the novel desk task indicate a functional relevance of spatial attention deficits in right-hemisphere stroke patients, even if they are “subclinical.” This should be considered especially in patients without obvious clinical neglect signs.

Multisensory stimulation in hemianopic patients boosts orienting responses to the hemianopic field and reduces attentional resources to the intact field.

Lateralised lesions can disrupt inhibitory cross-callosal fibres which maintain interhemispheric equilibrium in attention networks, with a consequent attentional bias towards the ipsilesional field. Some evidence of this imbalance has also been found in hemianopic patients (Tant et al., 2002). The aim of the present study was to reduce this attentional bias in hemianopic patients by using multisensory stimulation capable of activating subcortical structures responsible for orienting attention, such as the superior colliculus. Eight hemianopic patients underwent a course of multisensory stimulation treatment for two weeks and their behavioural and electrophysiological performance was tested at three time intervals: baseline 1 (before treatment), control baseline 2 (two weeks after baseline 1 and immediately before treatment as a control for practice effects) and finally after treatment. The results show improvements on various clinical measures, on orienting responses in the hemianopic field, and a reduction of electrophysiological activity (P3 amplitude) in response to stimuli presented in the intact visual field. These results suggest that the primary visual deficit in hemianopic patients might be accompanied by an ipsilesional attentional bias which might be reduced by multisensory stimulation.

Effects of prismatic adaptation on spatial gradients in unilateral neglect: A comparison of visual and auditory target detection with central attentional load

Prismatic adaptation is increasingly recognised as an effective procedure for rehabilitating symptoms of unilateral spatial neglect – producing relatively long-lasting improvements on a variety of spatial attention tasks. The mechanisms by which the aftereffects of adaptation change neglect patients’ performance on these tasks remain controversial. It is not clear, for example, whether adaptation directly influences the pathological ipsilesional attention bias that underlies neglect, or whether it simply changes exploratory motor behaviour. Here we used visual and auditory versions of a target detection task with a secondary task at fixation. Under these conditions, patients with neglect demonstrated a spatial gradient in their ability to orient to the brief, peripheral visual or auditory targets. Following prism adaptation, we found that overall performance on both the auditory and visual task improved, however, most patients in our sample did not show changes in their visual or auditory spatial gradient of attention, despite adequate aftereffects of adaptation and significant improvement in neglect on visual cancellation. Although there were individual cases that suggested prism-induced changes in visual target detection, and even reversal of the visual spatial gradient, such cases were not evident for the auditory modality. The findings indicate that spatial gradients in stimulus-driven attention may be less responsive to the effects of prism adaptation than neglect symptoms in voluntary orienting and exploratory behaviour. Individual factors such as lesion site and symptom severity may also determine the expression of prism effects on spatial neglect.

Competition between simultaneous stimuli modulated by location probability in hemispatial neglect

Many aspects of spatial neglect can be explained as arising from competition for attentional selection, with salient ipsilesional stimuli emerging as the winner more often than contralesional stimuli. The outcome of the competition, however, can be affected both by bottom-up perceptual factors such as the gestalt properties of the display and by top-down factors such as expectancy or stimulus blocking. This study examines whether the competition for attentional selection can be modulated by manipulating the probability of the target's location in hemispatial neglect. Five patients with left-sided hemispatial neglect and a group of control participants performed a visual target discrimination task. In equal probability blocks, the target appeared randomly in any of six possible horizontal locations (three left, three right) whereas in biased blocks, the target appeared in the mid-location on the left on 50% of the trials and in each of the other locations on 10% of the trials. The target appeared either alone or was accompanied by a distractor on the opposite side. The results showed that the spatial bias facilitated detection of all left-sided targets in the neglect group, but was more spatially specific in the control group. Furthermore, while distractors on either side interfered with target processing in both groups, the patterns differed across the visual field. Finally, the magnitude of facilitation due to the bias was greatest in the condition with the most inhibition, i.e. a left-sided target accompanied by a right-sided distractor in the neglect group. These data underscore the competitive push–pull relationship between different bottom-up and top-down attentional factors, particularly within neglect patients, in whom a strong ipsilesional attentional bias already exists.

Time-dependent activation of parieto-frontal networks for directing attention to tactile space. A study with paired transcranial magnetic stimulation pulses in right-brain-damaged patients with extinction.

Tactile extinction has been interpreted as an attentional disorder, closely related to hemineglect, due to hyperactivation of the unaffected hemisphere, resulting in an ipsilesional attentional bias. Paired transcranial magnetic stimulation (TMS) techniques, with a subthreshold conditioning stimulus (CS) followed at various interstimulus intervals (ISIs) by a suprathreshold test stimulus (TS), are useful for investigating intracortical inhibition and facilitation in the human motor cortex. In the present work, we investigated the effects of paired TMS over the posterior parietal and frontal cortex of the unaffected hemisphere in a group of eight right-brain-damaged patients with tactile extinction who were carrying out a bimanual tactile discrimination task. The aim of the study was to verify if paired TMS could induce selective inhibition or facilitation of the unaffected hemisphere depending on the ISI, resulting, respectively, in an improvement and a worsening of contralesional extinction. In addition, we wanted to investigate if the effects of parietal and frontal TMS on contralesional extinction appeared at different intervals, suggesting time-dependent activation in the cortical network for the processing of tactile spatial information. Paired TMS stimuli with a CS and a TS, separated by two ISIs of 1 and 10 ms, were applied over the left parietal and frontal cortex after various intervals from the presentation of bimanual cutaneous stimuli. Single-test parietal TMS stimuli improved the patients' performance, whereas paired TMS had distinct effects depending on the ISI: at ISI = 1 ms the improvement in extinction was greater than that induced by single-pulse TMS; at ISI = 10 ms we observed worsening of extinction, with complete reversal of the effects of single-pulse TMS. Compared with TMS delivered over the frontal cortex, parietal TMS improved the extinction rate in a time window that began earlier. These findings shed further light on the mechanism of tactile extinction, suggesting relative hyperexcitability of the parieto-frontal network in the unaffected hemisphere, which is amenable to study and modulation by paired TMS pulses. In addition, the results show time-dependent processing of tactile spatial information in the parietal and frontal cortices, with a bimodal distribution of activity, at least in the attentional network of the unaffected hemisphere.

Input and Response Determinants of Visual Extinction: A Case Study

We have studied a patient, CZ, with contralateral visual extinction due to a large ischaemic frontal-parietal-temporal lesion in the right hemisphere. We found that manipulation of intensity of the visual stimulus had little effect while an increase in eccentricity substantially increased extinction rate. An important factor was represented by the hemifield of stimulus presentation: when double stimuli were presented to the contralesional (left) hemifield, the leftmost stimulus was consistently extinguished while when stimuli were presented to the ipsilesional (right) hemifield, extinction was absent. Such effect was specific to hemifield rather than to head- and trunk-defined hemispace. Manipulation of response-related variables affected extinction to a large extent: In particular, the use of nonverbal responses diminished extinction considerably. This suggests that an important component of extinction may be represented by an impaired access of visual information to the left hemisphere. Finally, the RT results confirmed previous evidence of an ipsilesional attentional bias favouring, the rightmost stimuli both in the contralesional and in the ipsilesional hemifield.

Residual rightward attentional bias after apparent recovery from right hemisphere damage: implications for a multicomponent model of neglect.

Unilateral neglect may be a multicomponent attentional disorder consisting of an initial automatic orienting of attention toward the ipsilesional side and a subsequent impairment in contralesionally reorienting attention, both of which are superimposed on a generalised reduction in attention resources. It has been hypothesised that patients' ability to reorient attention contralesionally may recover relatively quickly, but that the ipsilesional attention bias may be relatively persistent. This hypothesis was tested by consecutively examining 13 patients who had had a right hemisphere stroke, and who had left unilateral neglect. They were examined once shortly after the stroke and again 12 months later, using a battery of standard clinical and experimental tasks. Patients initially showed a strong and consistent rightward attentional bias in addition to a failure to reorient their attention leftward. After 12 months patients continued to show an abnormal ipsilesional attentional bias, though most were now able to fully reorient their attention toward the contralesional side. These results suggest that restitution of the capacity to reorient attention contralesionally may underlie the apparent recovery from clinical signs of unilateral neglect. The presence of a residual ipsilesional attentional bias in most patients, however, may, at least in part, account for the poor functional outcomes in some apparently "recovered" patients.