Unilateral Spatial Neglect Patients Research Articles

Innovative Therapy Combining Neck Muscle Vibration and Transcranial Direct Current Stimulation in Association with Conventional Rehabilitation in Left Unilateral Spatial Neglect Patients: HEMISTIM Protocol for a Randomized Controlled Trial

Unilateral spatial neglect (USN) rehabilitation requires the development of new methods that can be easily integrated into conventional practice. The aim of the HEMISTIM protocol is to assess immediate and long-term recovery induced by an innovative association of left-side neck-muscle vibration (NMV) and anodal transcranial Direct Current Stimulation (tDCS) on the ipsilesional posterior parietal cortex during occupational therapy sessions in patients with left USN. Participants will be randomly assigned to four groups: control, Left-NMV, Left-NMV + sham-tDCS or Left-NMV + anodal-tDCS. NMV and tDCS will be applied during the first 15 min of occupational therapy sessions, three days a week for three weeks. USN will be assessed at baseline, just at the end of the first experimental session, after the first and third weeks of the protocol and three weeks after its ending. Our primary outcome will be the evolution of the functional Catherine Bergego Scale score. Secondary outcome measures include five tests that investigate different neuropsychological aspects of USN. Left NMV, by activating multisensory integration neuronal networks, might enhance effects obtained by conventional therapy since post-effects were shown when it was combined with upper limb movements. We expect to reinforce lasting intermodal recalibration through LTP-like plasticity induced by anodal tDCS.

Barriers to patient recruitment in a poststroke neurorehabilitation multicenter trial in Brazil

There is a high demand for stroke rehabilitation in the Brazilian public health system, but most studies that have addressed rehabilitation for unilateral spatial neglect (USN) after stroke have been performed in high-income countries. Therefore, the aim of this study was to analyze USN patient recruitment in a multicenter noninvasive brain stimulation clinical trial performed in Brazil and to provide study design recommendations for future studies. We evaluated the reasons for exclusion of patients from a multicenter, randomized, double-blinded clinical trial of rehabilitation of USN patients after stroke. Clinical and demographic variables were compared between the included and excluded patients. A descriptive statistical analysis was performed. Only 173 of the 1953 potential neglect patients (8.8%) passed the initial screening. After screening evaluation, 87/173 patients (50.3%) were excluded for clinical reasons. Cognitive impairment led to the exclusion of 21/87 patients (24.1%). Low socioeconomic status led to the exclusion of 37/173 patients (21.4%). Difficulty obtaining transportation to access treatment was the most common reason for their exclusion (16/37 patients, 43.3%). The analyzed Brazilian institutions have potential for conducting studies of USN. The recruitment of stroke survivors with USN was restricted by the study design and limited financial support. A history of cognitive impairment, intracranial stenting or craniectomy, and lack of transportation were the most common barriers to participating in a multicenter noninvasive brain stimulation trial among patients with USN after stroke.

A Proposal for a New Index to Quantify the Ratio of Near and Far Spatial Neglect Using Immersive Virtual Reality Technology: A Technical Report.

Unilateral spatial neglect (USN) is defined as impaired attention to sensory stimuli on one side, which can exist for near and far spaces combined or independently. Thus, quantifying both near- and far-space neglect is crucial. This study aims to propose an index to quantify the near/far spatial neglect ratio to describe the USN symptoms' characteristics in each patient using immersive virtual reality (VR) technology. An object-detecting task was performed for five USN patients in a three-dimensional VR space. The examiner recorded the positional data of the objects that were recognized by the USN patient using coordinate data. The near/far ratio (NFRatio) was calculated using the proposed equation to quantify the difference in neglect severity in near and far spaces of each patient. Among the patients, four tended to have greater far-space neglect, and one tended to have greater near-space neglect. Moreover, the near/far spatial neglect ratio was shown to vary according to height. This is the first study to propose immersive VR to quantify the near and far spatial neglect. However, further study is needed to assess its reliability and validity and describe its clinical usability. Clinical Relevance- In clinical practice USN symptoms cause neglected symptoms in 3D space so the proposed system will be of high clinical significance if 3D assessment is realized.

The attention atlas virtual reality platform maps three-dimensional (3D) attention in unilateral spatial neglect patients: a protocol.

Deficits in visuospatial attention, known as neglect, are common following brain injury, but underdiagnosed and poorly treated, resulting in long-term cognitive disability. In clinical settings, neglect is often assessed using simple pen-and-paper tests. While convenient, these cannot characterise the full spectrum of neglect. This protocol reports a research programme that compares traditional neglect assessments with a novel virtual reality attention assessment platform: The Attention Atlas (AA). The AA was codesigned by researchers and clinicians to meet the clinical need for improved neglect assessment. The AA uses a visual search paradigm to map the attended space in three dimensions and seeks to identify the optimal parameters that best distinguish neglect from non-neglect, and the spectrum of neglect, by providing near-time feedback to clinicians on system-level behavioural performance. A series of experiments will address procedural, scientific, patient, and clinical feasibility domains. Analyses focuses on descriptive measures of reaction time, accuracy data for target localisation, and histogram-based raycast attentional mapping analysis; which measures the individual's orientation in space, and inter- and intra-individual variation of visuospatial attention. We will compare neglect and control data using parametric between-subjects analyses. We present example individual-level results produced in near-time during visual search. The development and validation of the AA is part of a new generation of translational neuroscience that exploits the latest advances in technology and brain science, including technology repurposed from the consumer gaming market. This approach to rehabilitation has the potential for highly accurate, highly engaging, personalised care.

Virtual reality for the assessment and rehabilitation of neglect: where are we now? A 6-year review update

Unilateral spatial neglect (USN) is a frequent repercussion of a cerebrovascular accident, typically a stroke. USN patients fail to orient their attention to the contralesional side to detect auditory, visual, and somatosensory stimuli, as well as to collect and purposely use this information. Traditional methods for USN assessment and rehabilitation include paper-and-pencil procedures, which address cognitive functions as isolated from other aspects of patients’ functioning within a real-life context. This might compromise the ecological validity of these procedures and limit their generalizability; moreover, USN evaluation and treatment currently lacks a gold standard. The field of technology has provided several promising tools that have been integrated within the clinical practice; over the years, a “first wave” has promoted computerized methods, which cannot provide an ecological and realistic environment and tasks. Thus, a “second wave” has fostered the implementation of virtual reality (VR) devices that, with different degrees of immersiveness, induce a sense of presence and allow patients to actively interact within the life-like setting. The present paper provides an updated, comprehensive picture of VR devices in the assessment and rehabilitation of USN, building on the review of Pedroli et al. (2015). The present paper analyzes the methodological and technological aspects of the studies selected, considering the issue of usability and ecological validity of virtual environments and tasks. Despite the technological advancement, the studies in this field lack methodological rigor as well as a proper evaluation of VR usability and should improve the ecological validity of VR-based assessment and rehabilitation of USN.

CLINICAL AND DEMOGRAPHIC PREDICTORS OF UNILATERAL SPATIAL NEGLECT RECOVERY AFTER PRISM THERAPY AMONG STROKE SURVIVORS IN THE SUB-ACUTE PHASE OF RECOVERY

Background and Aims Unilateral Spatial Neglect (USN) affects rehabilitation process and leads to poor outcomes after stroke. Intervention for USN treatment has been suggested such as prism therapy (PA). However, factors that influence USN recovery has not been investigated. This study investigated the predictors of USN recovery after prism therapy. Methods This study was a single-blinded randomised controlled trial. USN was assessed with the conventional subset of the behavioural inattention test (BIT-C). A total of 74 USN patients who presented with USN following right-brain damage were divided into prism (n = 37) and control (n = 37) groups. Prism group used 20 dioptre prism lenses for repeated aiming, for 12 sessions, the control group used neutral lenses for similar aiming training. Clinical recovery was defined as BIT-C score>129: recovery, BIT-C score< 129: No recovery. Logistic regression was done to establish significant variable in the prediction recovery after PA. Results There were significantly greater improvement of BIT-C in the intervention group post treatment (P≤0.001). Predictor variables considered in this study was cognitive ability (assessed using the mini-mental scale), gender, age, years of education, race, employment status, handedness, type of stroke, site of stroke and site of stroke. Cognitive ability (OR =1.52, CI=1.08-2.14, p= 0.016) was found to significantly influence recovery following PA treatment. Conclusions This study highlights the characteristics of stroke patient that will most likely benefit from a PA treatment regimen. Higher cognitive ability was implicated to be a factor for USN recovery after PA treatment post-stroke.

Measuring Gaze and Arrow Cuing Effects With a Short Test Adapted to Brain Damaged Patients With Unilateral Spatial Neglect: A Preliminary Study.

People with left unilateral spatial neglect (USN) following a right brain lesion show difficulty in orienting their attention toward stimuli presented on the left. However, cuing the stimuli with gaze direction or a pointing arrow can help some of them to compensate for this difficulty. In order to build a tool that helps to identify these patients, we needed a short version of the paradigm classically used to test gaze and arow cuing effects in healthy adults, adapted to the capacities of patients with severe attention deficit. Here, we tested the robustness of the cuing effects measured by such a short version in 48 young adult healthy participants, 46 older healthy participants, 10 patients with left USN following a right brain lesion (USN+), and 10 patients with right brain lesions but no USN (USN–). We observed gaze and arrow cuing effects in all populations, independently of age and presence or absence of a right brain lesion. In the neglect field, the USN+ group showed event greater cuing effect than older healthy participants and the USN– group. We showed that gaze and arrow cuing effects are powerful enough to be detected in a very short test adapted to the capacities of older patients with severe attention deficits, which increases their applicability in rehabilitation settings. We further concluded that our test is a suitable basis to develop a tool that will help neuropsychologists to identify USN patients who respond to gaze and/or arrow cuing in their neglect field.

Exploring the time-course and the reference frames of adaptation to optical prisms and its aftereffects

Prism adaptation (PA) is used to investigate visuo-motor plasticity and to rehabilitate the syndrome of Unilateral Spatial Neglect (USN). After PA, participants show aftereffects (AEs), contralateral to the side of the optical displacement in several tasks. This study explored the features of these AEs, specifically the “egocentric” versus “allocentric, object-based”, reference frames involved, and their time course. In three experiments, healthy participants adapted to prismatic lenses inducing a horizontal displacement of the visual field. In Experiment #1, participants adapted to rightward displacing prisms. Four tasks were used requiring repeated pointings towards the participant's subjective egocentric straight-ahead, with the availability of proprioceptive or visual-proprioceptive signals, and, in some conditions, of an external allocentric visual frame (i.e., a rectangular paper sheet). Experiment #2 explored the role of the position of the allocentric frame, with AEs being tested by straight-ahead and frame bisection tasks, requiring pointing toward the external visual frame, placed in different positions of the working space. An egocentric visual proprioceptive task was administered after prism removal and after the execution of the allocentric tasks, to assess the effectiveness of the PA, as indexed by the AEs, and their persistence up to the end of the administration of the allocentric tasks. Experiment #3 differed from #2 in that participants adapted to leftward displacing lenses. Consistent with evidence from USN patients, in Experiment #1, in the egocentric tasks, AEs lasting up to 30 min after PA were found. In Experiment #2, AEs in “allocentric” tasks did not occur, regardless of frame position. Experiment #3 showed AEs in both the “egocentric” and the “allocentric” tasks, with the latter being minor in size. These findings illustrate that the spatial reference systems modulated by PA in extra-personal space primarily operate in spatial “egocentric” reference frames, with a comparatively minor and direction-specific role of “allocentric” frames.

The presence of semantic content in a visual recognition memory task reduces the severity of neglect

Patients with right hemisphere damage often show a lateral bias when asked to report the left side of mental images held in visual working memory (i.e. representational neglect). The neural basis of representational neglect is not well understood. One hypothesis suggests that it reflects a deficit in attentional-exploratory mechanisms, i.e. an inability to direct attention to the left side of the image. Another proposition states that intact visual working memory (VWM) is necessary for correctly creating a mental image. Here we examined two components of VWM in patients with unilateral spatial neglect (USN): memory for identity, and memory for spatial position. We manipulated the strength of memory representations by presenting two distinct categories of objects, in separate blocks. These were familiar namable objects (fruits, etc.), and unfamiliar abstract objects. The former category elicits stronger working-memory traces, thanks to preexisting visual and semantic representations in long-term memory. We hypothesized that if USN patients show a lateralized deficit in VWM, it should be more pronounced for abstract objects, due to their weaker working-memory traces. Importantly, to isolate a spatially lateralized deficit in memory from a failure to fully perceive the object-arrays, we ensured that all included patients perceived every item during the encoding phase. We used a working-memory task: participants viewed object arrays and had to memorize items' identities and spatial positions. Then, single objects were presented requiring ‘old/new’ recognition, and retrieval of ‘old’ items’ original positions. Our results show a lateral bias in patients’ recognition-memory performance. Remarkably, it was threefold milder for namable objects compared to abstract objects. We conclude that VWM lateralized deficit is substantial in USN patients and could play a role in representational neglect.

Effect of Prism Adaptation Therapy on the Activities of Daily Living and Awareness for Spatial Neglect: A Secondary Analysis of the Randomized, Controlled Trial.

Background: Rehabilitation for unilateral spatial neglect (USN) using prism adaptation (PA) is one of the most widely used methods, and the effectiveness of PA is well-evidenced. Although the effect of PA generalized various neglect symptoms, the effectiveness for some aspects of neglect is not fully proven. The Catherine Bergego Scale (CBS) was developed to identify problems with the activities of daily living (ADL) caused by USN. The CBS is composed of 10 observation assessments and a self-assessment questionnaire. To assess the self-awareness of USN, the anosognosia score is calculated as the difference between the observational scores and the self-assessment scores. To investigate how PA affects ADL and self-awareness in subacute USN patients during rehabilitation, we analyzed each item of the CBS and self-awareness from a randomized, controlled trial (RCT) that we previously conducted (Mizuno et al., 2011). Methods: A double-masked randomized, controlled trial was conducted to evaluate the effects of a 2-week PA therapy on USN in 8 hospitals in Japan. We compared each item of the CBS, anosognosia score, and absolute value of the anosognosia score between the prism group and the control group. Results: Two of ten items (gaze orientation and exploration of personal belongings) were significantly improved in the prism group compared with those in the control group. The absolute value of the anosognosia score was significantly improved by PA. Conclusions: Improvement of oculomotor exploration by PA may generalize the behavioral level in a daily living environment. This study suggested that PA could accelerate the self-awareness of neglect during subacute rehabilitation.

Influence of right versus left unilateral spatial neglect on the functional recovery after rehabilitation in sub-acute stroke patients

ABSTRACT Unilateral spatial neglect (USN) may lead to poor functional rehabilitation outcomes. However, studies investigating the rehabilitation outcomes of right-sided USN are lacking. We aimed to investigate (1) the clinical impacts of USN, including right-sided USN, for stroke patients in sub-acute rehabilitation, and (2) evaluate the differences in clinical characteristics and rehabilitation outcomes between right- and left-sided USN patients. We retrospectively screened the medical records of 297 inpatients at the Tokyo-Bay Rehabilitation Hospital who experienced a cerebrovascular accident with supratentorial lesions between January 1st, 2014 and December 31st, 2016. We performed independent multiple regression analysis in patients with left and right hemisphere damage. The Behavioral Inattention Test was a significant independent variable for predicting the motor, cognitive, and total functional independence measure (FIM), compared to the Stroke Impairment Assessment Set and Mini-Mental State Examination. USN affects motor FIM recovery more than cognitive FIM recovery regardless of the damaged hemisphere. Our study results confirm that both right- and left-sided USN influence the functional recovery of stroke patients. USN occurs, slightly less frequently, following a left hemisphere stroke. However, USN negatively affected rehabilitation outcomes, regardless of the neglected side. Therefore, USN treatment is necessary for patients with left and right hemisphere damage.

Multisensory stimulation for the rehabilitation of unilateral spatial neglect

ABSTRACT Unilateral spatial neglect (USN) is a neuropsychological syndrome, typically caused by lesions of the right hemisphere, whose features are the defective report of events occurring in the left (contralesional) side of space and the inability to orient and set up actions leftwards. Multisensory integration mechanisms, largely spared in USN patients, may temporally modulate spatial orienting. In this pilot study, the effects of an intensive audio-visual Multisensory Stimulation (MS) on USN were assessed, and compared with those of a treatment that ameliorates USN, Prismatic Adaptation (PA). Twenty USN stroke patients received a 2-week treatment (20 sessions, twice per day) of MS or PA. The effects of MS and PA were assessed by a set of neuropsychological clinical tests (target cancellation, line bisection, sentence reading, personal neglect, complex drawing) and the Catherine Bergego Scale for functional disability. Results showed that MS brought about an amelioration of USN deficits overall comparable to that induced by PA; personal neglect was improved only by MS, not by PA. The clinical gains of the MS treatment were not influenced by duration of disease and lesion volume, and they persisted up to one month post-treatment. In conclusion, MS represents a novel and promising rehabilitation procedure for USN.

The Brentano Illusion Test (BRIT): An implicit task of perceptual processing for the assessment of visual field defects in neglect patients

ABSTRACT In brain damaged patients with unilateral spatial neglect (USN), the differential diagnosis between the presence and absence of a unilateral visual half-field deficit (VHFD) is hampered by the similarity of their phenomenology. The absence of stimuli detection in the contralateral visual field, indeed, can be due to the co-occurrence of USN and VHFD or the sole presence of the USN. The disentangling of the two conditions is required to devise more specific rehabilitation programmes. Daini et al. [2002. Exploring the syndrome of spatial unilateral neglect through an illusion of length. Experimental Brain Research, 144(2), 224–237.] reported a difference in performance for the two conditions when the tasks required the bisection of Brentano illusory stimuli. Only when USN and VHFD co-occurred, the leftward illusory effect was disrupted. Based on previous findings, in this cross-sectional study, we developed the Brentano Illusion Test (BRIT), a clinical tool that helps the identification of VHFD in USN patients. The BRIT is a simple behavioural test of line bisection aimed at verifying the presence or absence of implicit processing in USN and thus helping the diagnosis of VHFD in USN patients; it also provides normative data for the line bisection task and the length effect.

Effect of prism adaptation on neglect hemianesthesia

Prism adaptation (PA) has proven to be effective in alleviating many signs of unilateral spatial neglect (USN). Generally, the principal improvement after PA treatment was found to be in the high-level cognitive function. Nevertheless, some evidence has also been found for it in somatosensory function. We have aimed to test the influence of PA on neglect hemianesthesia, a condition in which the high-level neglect-related deficit mimics hemianesthesia. Twenty-one USN patients were enrolled in the study. Each patient performed two sessions of PA, one with neutral glasses and one with prism glasses using a cross-over design. Sensitivity on the upper limb was tested using two methods. The first task was the sensibility subtest which was derived from the standard clinical examination. The second was the perceptual and motor electro-cutaneous threshold on the forearms using an electro-cutaneous stimulator. Four neuropsychological tests were used to diagnose USN and to check improvement: Star cancellation, Line bisection, Sentence reading and the Comb & Razor test. Comparing prism with sham conditions, our results show significant improvements in double extinction and in the electro-cutaneous perceptual threshold only for the contralesional hand. No improvement was found for the ipsilesional hand, for the motor threshold, and for neutral glasses. Significant improvement was found in personal neglect. Replication of the task in a subgroup of patients confirmed the primary results. The improvements in somatosensory perception together with the amelioration of personal neglect suggest that PA also has a specific effect on the neglect hemianesthesia.

Exploring prism exposure after hemispheric damage: Reduced aftereffects following left-sided lesions

Prism adaptation is a well-known method used to investigate brain plasticity, and a promising technique for the rehabilitation of unilateral spatial neglect (USN). Only little evidence about the mechanisms of prism adaptation (PA) in patients with left-brain damage is on record, and about putative differences of PA, and the aftereffects (AEs), between patients with left and right brain damage. In the present study, PA and the AEs were assessed in 30 brain-damaged patients, 20 with right-sided lesions (10 with and 10 without USN), and 10 with left-sided lesions without USN, as well as in a control group of 24 age-matched participants. All patients underwent adaptation to lenses shifting the field of vision towards the side of the lesion, followed by two measures for detecting AEs: the proprioceptive (P) and the visuo-proprioceptive (VP) straight-ahead tasks. To investigate the temporal course of AEs in the different groups, the two measures were recorded immediately and 10 min after PA. Before PA, and at the end of the 10-min delayed evaluation, two tasks to assess USN (target cancellation and drawing) were also administered. All patients adapted to prisms. However, left-brain-damaged (LBD) patients presented with reduced AEs, as compared with right-brain-damaged (RBD) patients with USN. Moreover, while both controls and LBD patients adapting to left-shifting prisms had reduced VP AEs in the delayed condition, AEs were not different from zero (i.e., no AEs) in LBD patients. Finally, in the delayed condition USN patients showed an improvement in the drawing, but not in the cancellation, tasks. These results suggest that adaptation to leftward shifting lenses is associated with larger decay of VP AEs, and a role of the left hemisphere in maintaining these AEs after PA. These findings can be of relevance for the clinical application of this technique in neurological populations.

Left unilateral neglect is greater for non-namable than for namable objects in recognition memory

Patients with right hemisphere damage often fail to notice, respond to, and report on left-sided stimuli, a condition termed unilateral spatial neglect (USN). In a previous study, we found that USN patients showed a significant contralesional disadvantage both in immediate recall and in delayed recognition of presented visual objects. However, successful verbal recall of an object immediately after its presentation eliminated to a large extent the effect of the spatial position on delayed recognition. Our aim in the present study was to assess whether the formation of a verbal memory trace is responsible for the attenuation of the lateralized bias in recognition of objects that have been verbally recalled. To this end, we compared the immediate recognition performance of 16 USN patients and 16 control subjects for two categories of pictures: namable objects (fruits, furniture, etc.) vs. abstract colorful non-namable pictures. Both healthy controls and USN patients showed a better mean general performance for objects than for abstract pictures (controls: discrimination rate d’namable objects: mean ± standard deviation 3.20 ± 0.86, d’non-namable 2.05 ± 0.73; USN patients d’namable 1.61 ± 0.68; d’non-namable 0.98 ± 0.58). Laterality index [LI = (d’Left- d’Right)/(d’Left+ d’Right)] revealed a greater lateralized bias for abstract pictures than for object pictures in USN patients (USN patients: mean LInamable: −0.14 ± 0.15; mean LI non-namable: −0.42 ± 0.27; controls: mean LInamable: −0.01 ± 0.06; mean LI non-namable: 0.06 ± 0.11). Semantic processing modulates the spatial biases exhibited by USN patients in recognition memory, even in the lack of an explicit verbal recall task; left-sided information is partially perceived and might be more accessible when coded dually - both verbally and visually. The use of verbalization as a rehabilitation technique in USN deserves further investigation.

The study of event-related potentials in unilateral spatial neglect

To compare the amplitude and latency of P1, N1, P2, N2, P300 between the unilateral spatial neglect patients after right hemisphere stroke and normal people, in order to study the spatial attention processing characteristic of unilateral spatial neglect patients, further to explore the mechanism of USN. Twenty cases (10 USN patients and 10 normal people) were enrolled in the study. We recorded the ERP, and then compared the reaction time and correct rate, the amplitude and latency of P1, N1, P2, N2, P300 when the target appeared in the left and right, to study the mechanism of USN. The correct rate of the USN group was lower than the Normal group. There were no significant differences between the two groups in P1 amplitude and N2 amplitude. The N1 and P2 amplitude of right hemisphere of the USN group was lower than the normal group. When the target appeared in the left, the P300 amplitude of the USN group was lower than the normal group. The latency of P1, N1, P2, N2, P300 in the USN group was prolonged than the normal group. During the spatial attention processing, regardless of the stimulus from the left or right, the information processing speed of the USN group slowed down compared with the normal group. In the early stage, there was no significant reduction of activitied neurons. In the mid-stage, the number of activitied neurons was reduced significantly in the right hemisphere. But in the late stage, the number of activitied neurons was reduced significantly when the stimulus from the left side.

A comparison of prism adaptation with terminal versus concurrent exposure on sensorimotor changes and spatial neglect

ABSTRACTPrism adaptation (PA) is a technique that induces a temporary change of the alignment between different reference frames. This technique has been shown to reduce many signs of unilateral spatial neglect (USN). Two procedures of prism adaptation have been used. In concurrent exposure participants can see their arm and hand during the movement trajectory, and during terminal exposure, participants can see only the most distal few centimetres. Because the two exposures elicit different proportions of visual and proprioceptive realignment, they could present different rehabilitation efficacies. We compared these procedures in 12 USN patients and 12 healthy participants who performed one session of PA with concurrent exposure and one session with terminal exposure. We compared the effects of the two exposure types on sensorimotor outcomes (visual subjective straight ahead, proprioceptive subjective straight ahead, open loop pointing, and error correction during exposure) and neglect outcomes. We found no significant differences in the effects of the two exposure types on sensorimotor performance of patients and controls, nor on patients’ neuropsychological outcomes. Compared with controls, USN patients showed a significant rightward bias in visual subjective straight ahead pre-adaptation, a slower rate of error correction during prism exposure, and some evidence that visual and proprioceptive shift could be influenced by their neglect. Based on these results, we recommend that prism adaptation be conducted with concurrent exposure for easiness of execution.

Head Position of Patients with Right Hemisphere Damage during a Visual Search Task in a Large Field

Spatial neglect syndrome with cerebral lesions is characterized by the ina-bility to orient, report, or respond to relevant visual stimuli contralateral to the lesions. In this study, we investigated the pattern of horizontal visual search in a large space; this search was performed by patients with right hemisphere damage caused by cerebrovascular disease. The neck rotation angle and search time in each increment were continuously recorded during the task, and quantitative data of the measurements were collected. Head position during the visual search task in a large space (%) was then calculated. We set angular bands in increments of 5 degrees from the midline on the left and right sides, and calculated the total search time in each angular band. In patients with unilateral spatial neglect (USN), the search time in the angular band of 5 - 9 on the right side was significantly longer (with USN 16.7%, without USN 4.5%, t = 2.52, df = 16, p < 0.05). Furthermore, in patients with neglect in the leftmost end area in a large space, the search time was significantly shorter in the angular band of 1 - 4 degrees to the left (with neglect 13.1%, without neglect 23.7%, t = 2.13, df = 16, p < 0.05), and tended to be long in the angular band of 5 - 9 to the right. The neck rotation angle and pattern during the search task in a large field deviated slightly to the right, and the search time slightly to the left was short. We believe that these results support the rightward deviation of the search pattern and frame of USN patients.

Multisensory integration in hemianopia and unilateral spatial neglect: Evidence from the sound induced flash illusion

Recent neuropsychological evidence suggests that acquired brain lesions can, in some instances, abolish the ability to integrate inputs from different sensory modalities, disrupting multisensory perception. We explored the ability to perceive multisensory events, in particular the integrity of audio-visual processing in the temporal domain, in brain-damaged patients with visual field defects (VFD), or with unilateral spatial neglect (USN), by assessing their sensitivity to the ‘Sound-Induced Flash Illusion’ (SIFI). The study yielded two key findings. Firstly, the ‘fission’ illusion (namely, seeing multiple flashes when a single flash is paired with multiple sounds) is reduced in both left- and right-brain-damaged patients with VFD, but not in right-brain-damaged patients with left USN. The disruption of the fission illusion is proportional to the extent of the occipital damage. Secondly, a reliable ‘fusion’ illusion (namely, seeing less flashes when a single sound is paired with multiple flashes) is evoked in USN patients, but neither in VFD patients nor in healthy participants. A control experiment showed that the fusion, but not the fission, illusion is lost in older participants (>50 year-old), as compared with younger healthy participants (<30 year-old). This evidence indicates that the fission and fusion illusions are dissociable multisensory phenomena, altered differently by impairments of visual perception (i.e. VFD) and spatial attention (i.e. USN). The occipital cortex represents a key cortical site for binding auditory and visual stimuli in the SIFI, while damage to right-hemisphere areas mediating spatial attention and awareness does not prevent the integration of audio-visual inputs in the temporal domain.