Impaired Visual Perception Research Articles

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.

Neural basis of visual perception and reasoning ability in Alzheimer's disease: correlation between Raven's Colored Progressive Matrices test and 123 I-IMP SPECT imaging results.

Impairment of visual perception frequently occurs in Alzheimer's disease (AD) and can cause severe constraints in daily activities. The nonverbal Raven's Colored Progressive Matrices (RCPM) test consists of sets A, AB, and B and is easily performed in a short time to evaluate both visual perception and reasoning ability. The purpose of this study was to evaluate the neural basis of visual perception and reasoning ability in patients with AD using RCPM and single-photon emission computed tomography (SPECT). Fifty patients who fulfilled the National Institute on Aging/Alzheimer's Association criteria for probable AD dementia were examined with RCPM and SPECT. All SPECTs were performed using N-isopropyl-p-[123 I]-iodoamphetamine. A multiple regression model was used to perform multivariate analyses of the relationships between regional cerebral blood flow (rCBF) and RCPM scores. There was a significant positive correlation between RCPM total score and rCBF in the inferior parietal lobes bilaterally, the right inferior temporal gyrus, and the right middle frontal gyrus. Set A was positively correlated with rCBF in the right temporal and right parietal lobes. Set AB was positively correlated with rCBF in the right temporal, right parietal, and right frontal lobes. Set B was positively correlated with rCBF in the right parietal and right frontal lobes. Our findings suggest that deteriorations of specific brain regions are associated with dysfunction of visual perception and reasoning ability in AD. RCPM is another informative assessment scale of cognition for use in patients with AD. Copyright © 2016 John Wiley & Sons, Ltd.

Slowed response to peripheral visual stimuli during strenuous exercise

Recently, we proposed that strenuous exercise impairs peripheral visual perception because visual responses to peripheral visual stimuli were slowed during strenuous exercise. However, this proposal was challenged because strenuous exercise is also likely to affect the brain network underlying motor responses. The purpose of the current study was to resolve this issue. Fourteen participants performed a visual reaction-time (RT) task at rest and while exercising at 50% (moderate) and 75% (strenuous) peak oxygen uptake. Visual stimuli were randomly presented at different distances from fixation in two task conditions: the Central condition (2° or 5° from fixation) and the Peripheral condition (30° or 50° from fixation). We defined premotor time as the time between stimulus onset and the motor response, as determined using electromyographic recordings. In the Central condition, premotor time did not change during moderate (167±19ms) and strenuous (168±24ms) exercise from that at rest (164±17ms). In the Peripheral condition, premotor time significantly increased during moderate (181±18ms, P<0.05) and strenuous exercise (189±23ms, P<0.001) from that at rest (173±17ms). These results suggest that increases in Premotor Time to the peripheral visual stimuli did not result from an impaired motor-response network, but rather from impaired peripheral visual perception. We conclude that slowed response to peripheral visual stimuli during strenuous exercise primarily results from impaired visual perception of the periphery.

Effectiveness of Interventions to Address Visual and Visual-Perceptual Impairments to Improve Occupational Performance in Adults With Traumatic Brain Injury: A Systematic Review.

Visual and visual-perceptual impairments occur frequently with traumatic brain injury (TBI) and influence occupational performance. This systematic review examined the effectiveness of interventions within the scope of occupational therapy to improve occupational performance for adults with visual and visual-perceptual impairments as a result of TBI. Medline, PsycINFO, CINAHL, OTseeker, and the Cochrane Database of Systematic Reviews were searched, and 66 full text articles were reviewed. Sixteen articles were included in the review. Strong evidence supports the use of scanning, limited evidence supports the use of adaptive strategies, and mixed evidence supports the use of cognitive interventions to improve occupational performance for adults with TBI. Evidence related to vision therapy varies on the basis of the specific intervention implemented. Although the strength of the research varied, implications are discussed for practice, education, and research.

The prevalence of visual hallucinations in non-affective psychosis, and the role of perception and attention.

Little is known about visual hallucinations (VH) in psychosis. We investigated the prevalence and the role of bottom-up and top-down processing in VH. The prevailing view is that VH are probably related to altered top-down processing, rather than to distorted bottom-up processing. Conversely, VH in Parkinson's disease are associated with impaired visual perception and attention, as proposed by the Perception and Attention Deficit (PAD) model. Auditory hallucinations (AH) in psychosis, however, are thought to be related to increased attention. Our retrospective database study included 1119 patients with non-affective psychosis and 586 controls. The Community Assessment of Psychic Experiences established the VH rate. Scores on visual perception tests [Degraded Facial Affect Recognition (DFAR), Benton Facial Recognition Task] and attention tests [Response Set-shifting Task, Continuous Performance Test-HQ (CPT-HQ)] were compared between 75 VH patients, 706 non-VH patients and 485 non-VH controls. The lifetime VH rate was 37%. The patient groups performed similarly on cognitive tasks; both groups showed worse perception (DFAR) than controls. Non-VH patients showed worse attention (CPT-HQ) than controls, whereas VH patients did not perform differently. We did not find significant VH-related impairments in bottom-up processing or direct top-down alterations. However, the results suggest a relatively spared attentional performance in VH patients, whereas face perception and processing speed were equally impaired in both patient groups relative to controls. This would match better with the increased attention hypothesis than with the PAD model. Our finding that VH frequently co-occur with AH may support an increased attention-induced 'hallucination proneness'.

Relationship between Comorbid Cognitive Impairment and Functional Outcomes in Stroke Patients with Spatial Neglect

Objective: The aim of this study was to investigate relationships between cognitive impairment and functional outcomes in stroke patients with spatial neglect. Method: Twenty seven right hemisphere ischemic stroke patients who admitted to an inpatient rehabilitation unit were included. Patients were divided into two group based on KF-NAP scores: Neglect group (n=18) and non-neglect group (n=9). Neglect group (n=18) were subdivided into two groups by discharge FIM scores as poor outcome group (n=8, <70) and good outcome group (n=10, ≥70). Cognitive function assessments including attention (Attention & Calculation, Digit span test–Forward), memory (Digit span test–Backward, SVLT-Immediate recalls/Delayed recalls) and visual perception (LOTCA-Visual perception/Visuomotor organization), and stroke severity assessment including NIHSS, FMA, K-MMSE, and FIM were performed. Cognitive impairments and functional outcomes were compared between two groups. Results: There were significant differences in NIHSS, FMA (affected U/E, affected L/E), discharge FIM, FIM gain and LOTCA-visuomotor organization between Neglect group and nonneglect group (p<0.05). Among the patients with spatial neglect, there were significant differences in KF-NAP, K-MMSE and assessment scores of memory and visual perception between poor outcome group and good outcome group. Attention, memory and visual perception were significantly correlated with KF-NAP scores (p<0.05). Conclusion: Stroke patients with spatial neglect showed more severe impairment in cognitive, motor and general functional status, which resulted in delayed functional recovery. Spatial neglect patients with combined memory and visual perception impairment may show poor functional outcome. (Brain & NeuroRehabilitation 2016; 9: 37-47)

Can Technology-Assisted Toilets Improve Quality of Life for Rehabilitating Stroke Patients? A Pilot Cohort Study

intraparenchymal hemorrhage. The patient was noted to have impairments in visual perception, memory, language and balance. The patient was diagnosed with Balint’s Syndrome, characterized by simultagnosia, occulomotor apraxia and optic ataxia. The patient required acute inpatient rehabilitation to address this unique set of impairments. Interventions: An interdisciplinary approach was utilized focusing on task-based training to improve his cognitive and physical functioning. The patient benefited from errorless learning techniques, a low stimulation environment, and proprioceptive input to improve balance and coordination. Main Outcome Measure(s): O-LOG, FIM, Berg Balance Test, and a specialized protocol for spaced retrieval of orientation information. Results: The patient demonstrated improvement in orientation (8/30 to 20/30 on O-LOG), balance (0/56 to 17/56 on Berg Balance Test), basic communication skills, and self-care activities over four weeks. Conclusions: These unique interventions led to functional improvement in this patient with Balint’s Syndrome as measured by objective scales. This case report demonstrates the necessity of an interdisciplinary rehabilitation approach for a patient with complex functional impairments. Limited clinical research exists regarding established approaches and additional studies are needed to validate an effective clinical approach for this unique syndrome.

Impairment of visual perception in Aging: Compensatory brain mechanisms

We have studied the effects of normal aging on visual perception and the existence of possible compensatory brain mechanisms. Were measured in three groups of 30 people with normal vision and average age of 19.6, 42.6 and 65.7 years, the response time to the presentation of stimuli (0.5º in diameter grey circles) sequentially in 24 positions of the visual field, distributed in 8 polar coordinates and 3 eccentricities (2.15, 3.83 and 5.53 degrees of visual field). The stimulus was presented for 100 milliseconds, with low and high contrast (6% and 78%, respectively). The experiments were conducted with and without covert attention to stimuli. With age was observed a progressive increase in the response times from the stimuli of 6% of contrast and those presented in the eccentricity of 5.53º. With covert attention, response times were significantly reduced in the three age groups. However, while the younger and older showed similar reductions in the response times, the adult group obtained minor cuts. These results show that during aging occurs a selective and progressive deterioration in the perception of low contrast and that this deterioration is greater in the peripheral macular areas and that from sixty years the visual attention compensating mechanisms have greater efficiency in the improvement of visual perception.

Impairment of visual perception in Aging: Compensatory brain mechanisms

We have studied the effects of normal aging on visual perception and the existence of possible compensatory brain mechanisms. Were measured in three groups of 30 people with normal vision and average age of 19.6, 42.6 and 65.7 years, the response time to the presentation of stimuli (0.5º in diameter grey circles) sequentially in 24 positions of the visual field, distributed in 8 polar coordinates and 3 eccentricities (2.15, 3.83 and 5.53 degrees of visual field). The stimulus was presented for 100 milliseconds, with low and high contrast (6% and 78%, respectively). The experiments were conducted with and without covert attention to stimuli. With age was observed a progressive increase in the response times from the stimuli of 6% of contrast and those presented in the eccentricity of 5.53º. With covert attention, response times were significantly reduced in the three age groups. However, while the younger and older showed similar reductions in the response times, the adult group obtained minor cuts. These results show that during aging occurs a selective and progressive deterioration in the perception of low contrast and that this deterioration is greater in the peripheral macular areas and that from sixty years the visual attention compensating mechanisms have greater efficiency in the improvement of visual perception.

Can They See It? The Functional Field of View Is Narrower in Individuals with Autism Spectrum Disorder.

Although social cognitive deficits have long been thought to underlie the characteristic and pervasive difficulties with social interaction observed in individuals with autism spectrum disorder (ASD), several recent behavioral and neuroimaging studies have indicated that visual perceptual impairments might also play a role. People with ASD show a robust bias towards detailed information at the expense of global information, although the mechanisms that underlie this phenomenon remain elusive. To address this issue, we investigated the functional field of view in a group of high-functioning children with autism (n = 13) and a paired non-ASD group (n = 13). Our results indicate that the ability to correctly detect and identify stimuli sharply decreases with greater eccentricity from the fovea in people with ASD. Accordingly, a probe analysis revealed that the functional field of view in the ASD group was only about 6.62° of retinal eccentricity, compared with 8.57° in typically developing children. Thus, children with ASD appear to have a narrower functional field of view. These results challenge the conventional hypothesis that the deficit in global processing in individuals with ASD is solely due to weak central coherence. Alternatively, our data suggest that a narrower functional field of view may also contribute to this bias.

Visual-perceptual impairment in children with cerebral palsy: a systematic review.

Visual perception is one of the cognitive functions often impaired in children with cerebral palsy (CP). The aim of this systematic literature review was to assess the frequency of visual-perceptual impairment (VPI) and its relationship with patient characteristics. Eligible studies were relevant papers assessing visual perception with five common standardized assessment instruments in children with CP published from January 1990 to August 2011. Of the 84 studies selected, 15 were retained. In children with CP, the proportion of VPI ranged from 40% to 50% and the mean visual perception quotient from 70 to 90. None of the studies reported a significant influence of CP subtype, IQ level, side of motor impairment, neuro-ophthalmological outcomes, or seizures. The severity of neuroradiological lesions seemed associated with VPI. The influence of prematurity was controversial, but a lower gestational age was more often associated with lower visual motor skills than with decreased visual-perceptual abilities. The impairment of visual perception in children with CP should be considered a core disorder within the CP syndrome. Further research, including a more systematic approach to neuropsychological testing, is needed to explore the specific impact of CP subgroups and of neuroradiological features on visual-perceptual development.

Relationship between visuo-perceptual function and manual dexterity in community-dwelling older adults.

[Purpose] The purpose of the present study was to examine the relationship between visual perceptual function and manual dexterity in community-dwelling older adults. [Subjects and Methods] Fifty-eight participants were recruited by convenience sampling from local rehabilitation centers. This was a cross-sectional study that used the following four clinical tools: the Mini-Mental State Examination, 9 Hole Pegboard, Box and Block Test, and Motor-free Visual Perception Test, Third Edition. [Results] The Motor-free Visual Perception Test, Third Edition and Mini-Mental State Examination correlated significantly and positively with Box and Block Test, and did correlate significantly and negatively with 9 Hole Pegboard. [Conclusion] The results of this study suggest that visual perceptual impairment and cognitive dysfunction may influence manual dexterity in older adults, and rehabilitation of upper extremity function, along with visual perception and cognitive training, may be beneficial for this population.

Visual hallucinations in Parkinson's disease: theoretical models.

One of the most challenging tasks in neuroscience is to be able to meaningfully connect information across the different levels of investigation, from molecular or structural biology to the resulting behavior and cognition. Visual hallucinations are a frequent occurrence in Parkinson's disease and significantly contribute to the burden of the disease. Because of the widespread pathological processes implicated in visual hallucinations in Parkinson's disease, a final common mechanism that explains their manifestation will require an integrative approach, in which consideration is taken across all complementary levels of analysis. This review considers the leading hypothetical frameworks for visual hallucinations in Parkinson's disease, summarizing the key aspects of each in an attempt to highlight the aspects of the condition that such a unifying hypothesis must explain. These competing hypotheses include implications of dream imagery intrusion, deficits in reality monitoring, and impairments in visual perception and attention.

Clock drawing test in a space-occupying process.

We read with great interest the article of van Munster et al on a dural fistula presenting as a treatable cause of cognitive impairment.1 The authors demonstrated a markedly impaired clock drawing test (CDT) before treatment, which completely normalized after therapy. By presenting a case vignette, we wish to emphasize that an impaired CDT—especially in a younger individual—can be an alarming sign to prompt further examination. A 43-year-old right-handed teacher noted difficulty in drawing graphs of functional equations during lessons. The complete clinical neurological examination including confrontation testing of visual fields was unremarkable. The mini-mental state test revealed a score of 29 of 30 with 1 point deducted for short-term recall. The CDT, however, showed marked impairment (Figure 1A). A subsequent magnetic resonance imaging demonstrated a space-occupying lesion in the left parietal lobe (Figure 1B), which was histologically a high-grade glioma at surgery. Figure 1. A, Impaired clock drawing test in a 43-year-old woman, which prompted magnetic resonance imaging. B, Magnetic resonance imaging with gadolinium reveals a space-occupying process in the left parietal lobe. The CDT has achieved widespread clinical use as a cognitive screening instrument.2 It complements the Mini-Mental State Examination and serves as an efficient screen for early detection of dementia and in monitoring cognitive function.2,3 In particular, the CDT evaluates organization and planning,4 executive function,2 and visual perception. In our patient, impaired visual perception due to the left parietal lobe lesion was likely responsible for the marked CDT finding. This case reminded us that in the field of neurohospitalist medicine, an impaired CDT can be a prominent and isolated clinical finding in a left hemisphere space-occupying lesion. As demonstrated by van Munster et al, an impaired CDT can return to normal after proper treatment.1

Effects of domain-specific noise on visual motion processing in schizophrenia.

BackgroundVisual perception impairments in schizophrenia stem from abnormal information processing. Information processing requires neural response to a stimulus (signal) against a backdrop of 1) random variation in baseline neural activity (internal noise) and sometimes irrelevant environmental stimulation (external noise). Filtering out noise is a critical aspect of information processing, and needs to be critically examined in schizophrenia.MethodsTo understand how noise in the visual system constrains perceptual processing, we devised a novel paradigm to build in both signal and external noise on same visual stimulus. Here, instead of uniformed noise, domain-specific noise—variations in stimulus speed—was introduced to evaluate the performance of schizophrenia patients in speed discrimination. Each motion stimulus—a random dot pattern (RDP) comprising 200 moving dots—included a range of speeds, drawn individually from a Gaussian distribution for each dot. The task for patients (n = 26) and controls (n = 28) was to identify which of two stimuli moved faster based on their mean speeds.FindingsPatients exhibited deficient speed discrimination at baseline, in the absence of speed noise. Their speed discrimination was further degraded in the presence of low and medium levels of external noise. In the presence of a high levels of noise, degradation of patients' speed discrimination leveled-off, resulting in similar performance to controls.ConclusionThese domain-specific noise effects on speed discrimination provide direct evidence for the existence of heightened internal noise within a specific visual motion processing domain in schizophrenia.

Impaired visual perception of hurtful actions in patients with chronic low back pain

Visually presented biological motion stimuli activate regions in the brain that are also related to musculo-skeletal pain. We therefore hypothesized that chronic pain impairs the perception of visually presented actions that involve body parts that hurt. In the first experiment, chronic back pain (CLBP) patients and healthy controls judged the lifted weight from point-light biological motion displays. An actor either lifted an invisible container (5, 10, or 15kg) from the floor, or lifted and manipulated it from the right to the left. The latter involved twisting of the lower back and would be very painful for CLBP patients. All participants recognized the displayed actions, but CLBP patients were impaired in judging the difference in handled weights, especially for the trunk rotation. The second experiment involved discrimination between forward and backward walking. Here the patients were just as good as the controls, showing that the main result of the first experiment was indeed specific to the sensory aspects of the task, and not to general impairments or attentional deficits. The results thus indicate that the judgment of sensorimotor aspects of a visually displayed movement is specifically affected by chronic low back pain.

Mining Association Rules for Neurobehavioral and Motor Disorders in Children Diagnosed with Cerebral Palsy.

Children diagnosed with cerebral palsy (CP) appear to be at high risk for developing neurobehavioral and motor disorders. The most common disorders for these children are impaired visual-perception skills and motor planning. Besides, they often have impaired executive functions, which can contribute to problematic emotional adjustment such as depression. Additionally, literature suggests that the tendency to develop these cognitive impairments and emotional abnormalities in pediatric CP is influenced by age and IQ. Because there are many other medical co-morbidities that can occur with CP (e.g., seizures and shunt placement), prediction of what percentages of patients will incur cognitive impairment and emotional abnormality is a difficult task. The purpose of this study was to investigate the associations between possible factors mentioned above, and neurobehavioral and motor disorders from a clinical database of pediatric subjects diagnosed with CP. The study resulted in 22 rules that can predict negative outcomes. These rules reinforced the growing body of literature supporting a link between CP, executive dysfunction, and subsequent neurobehavioral problems. The antecedents and consequents of some association rules were single factors, while other statistical associations were interactions of factor combinations. Further research is needed to include children's comprehensive treatment and medication history in order to determine additional impacts on their neurobehavioral and motor disorders.

Fonctions visuoperceptives chez les enfants IMC âgés de sept à 14 ans : groupement perceptif et discrimination figure–fond

Cognitive and perceptual disorders are commonly associated with the motor pathology in children with cerebral palsy (CP). Impairment of visual–perceptual functions is frequently reported in these children. These functions, however, play an important role in academic learning. Using the computerized battery BEVPS, we assessed three groups of children aged between 7 and 14 years, a CP group, a group matched on chronological age and a group matched for mental age (matched on Raven matrices) with CP group. In regarding to visuoperceptual functions, the perceptual grouping, figure–ground discrimination and local–global treatment processing abilities were assessed. The results showed that the perceptual grouping abilities of CP children were significantly lower in comparison with the children matched on chronological age and mental age when they had to process drawings silhouettes. In contrast, these performances are comparable between the three groups of children when they have to process line drawings. Furthermore, the deficits on figure–ground discrimination of CP children were observed when compared with children of the same chronological age for naming the drawings completely overlapping. Contrary, no difference was observed between the three groups for matching the drawings that were completely overlapping or for naming figures partially overlapping. Finally, the performances of the three groups were similar for the local and global information processing. These results therefore demonstrate the specificity of visual–perceptual impairment for these intermediate perceptual processing abilities in children with cerebral palsy, which seems to depend on the type of presentation of visual information.

Effects of Action Observation Training on Upper Extremity Function of Stroke Patients with Impaired Visual Perception and Cognition

이 연구는 시지각 및 인지기능 손상을 가진 뇌졸중 환자를 대상으로 동작관찰훈련을 제공하고, 손상 정도에 따라 상지기능 증진의 차이를 분석하고자 하였다. 뇌졸중 환자 103명을 대상으로 8주간, 주 5회, 회당 30분씩 동작관찰훈련을 제공하였다. 훈련 전에는 시지각 및 인지기능을, 훈련 전·후에는 상지기능을 평가하였다. 연구 결과, 시지각 및 인지기능 손상이 비교적 적었던 대상자의 상지기능이 손상이 많았던 대상자에 비해 높은 증진을 보였다. 상지기능은 시지각 및 인지기능과 유의한 관계를 보였고, 인지기능의 하위영역에서는 시지각, 사고조작, 운동실행, 공간지각, 시운동 조직화, 지남력 순으로 유의한 관계를 보였다. 즉, 동작관찰 훈련은 시지각 및 인지기능의 손상이 낮은 뇌졸중 환자에 비해 유의하게 높은 중재적 효과를 보였다. 따라서 시지각 및 인지기능 손상의 뇌졸중 환자에게 동작관찰훈련을 적용할 경우, 훈련 제공 전 사전평가를 통해 시지각 및 인지기능의 수준을 고려한 등급화를 시행해야 할 것으로 생각한다.

Brain Processing of Visual Information during Fast Eye Movements Maintains Motor Performance

Movement accuracy depends crucially on the ability to detect errors while actions are being performed. When inaccuracies occur repeatedly, both an immediate motor correction and a progressive adaptation of the motor command can unfold. Of all the movements in the motor repertoire of humans, saccadic eye movements are the fastest. Due to the high speed of saccades, and to the impairment of visual perception during saccades, a phenomenon called “saccadic suppression”, it is widely believed that the adaptive mechanisms maintaining saccadic performance depend critically on visual error signals acquired after saccade completion. Here, we demonstrate that, contrary to this widespread view, saccadic adaptation can be based entirely on visual information presented during saccades. Our results show that visual error signals introduced during saccade execution–by shifting a visual target at saccade onset and blanking it at saccade offset–induce the same level of adaptation as error signals, presented for the same duration, but after saccade completion. In addition, they reveal that this processing of intra-saccadic visual information for adaptation depends critically on visual information presented during the deceleration phase, but not the acceleration phase, of the saccade. These findings demonstrate that the human central nervous system can use short intra-saccadic glimpses of visual information for motor adaptation, and they call for a reappraisal of current models of saccadic adaptation.