Impaired Visual Perception Research Articles

Exploratory study of dorsal visual stream dysfunction in autism; A case series

BackgroundRobust neuroscientific evidence supports the existence of an association between autism and a visual motion processing deficit, arising from dysfunction of the dorsal visual stream, a pathway connecting the primary visual and parieto-occipital cortices. The neuro-ophthalmic consequences of dorsal visual stream dysfunction (DVSD) are well-described but seldom reported: simultanagnosia, optic ataxia (OA), and gaze apraxia. MethodThe clinical records of thirteen motor-impaired autistic children, with clinical diagnoses of DVSD, were retrospectively reviewed six years after DVSD diagnosis to determine the frequency and severity of their neuro-visual impairment. Two measures to rate severity of visual perceptual impairment were employed: frequency of parent-reported behaviours denoting impaired visual function, given as mean individual Cerebral Visual Impairment Inventory Scores (CVIS), and severity of age-inappropriate configural disruption of drawings, rated on Beery-VMI Visual Motor Integration standard scores (VMIS). Applying the 90th percentile cut-off CVIS of 0.74 for the typical population as marker of normal visual function a CVIS ≥ 2.5 indicated very severe impairment. Evidence was also sought for a correlation between central OA and severe motor coordination impairment (MCI), rated by the Beery Motor Coordination assessment, using method agreement analysis. ResultsSignificant correlation between CVIS and VMIS was determined by linear regression analysis: r = -0.81 [95% CI -0.94 to -0.47], p=0.0008. Agreement for MCI≤ 5th percentile with central OA, determined by Cohen’s weighted Kappa statistic (K), was significant: K = 1[95% CI: 0.46–1.54], p=0.0002. ConclusionsWe conclude that mechanisms driving OA (which is defined as ‘impaired visually guided movement’) may underpin severe motor impairment, in autism. CVIS and VMIS may be useful indicators of severity of spatial cognitive impairment.

Motion perception, form discrimination and visual motor integration abilities in mTBI patients

Although former studies demonstrated that patients with mild traumatic brain injuries (mTBI) have abnormal visual motion sensitivityand motor difficulties (Spiegel et al., 2016), little is known about the effect of mTBI on form perception and visual motor integration. The aim of this study was to evaluate temporal resolution, motion, form, form-from motion perception and visual motor integration in mTBI patients. Eleven mTBI patients (2 females, mean age 22.8 years) and ten age-matched controls (4 females) participated in the study. Motion perception was evaluated with the motion coherence test (MC). Temporal resolution was evaluated with the critical flicker fusion test (CFF). Form discrimination was assessed with form coherence test (FC) and form-from-motion test (FFM). VMI-6 was used to evaluate visual motor integration. The MC, FC, and FFM were displayed in a foveal position, while CFF was assessed in central and peripheral positions. Generalized linear models evidenced differences between mTBI and controls in CFF test and in VMI tasks. In details, in CFF test the mTBI patients had lower performances in peripheral temporal resolution processing as compared to controls and in VMI-6 test they had lower motor and visual motor integration abilities. No difference was found between mTBI patients and controls in MC, FC, and FFM tasks showing similar performance in mTBI and controls in motion, form and form from motion perception. These results demonstrated that mTBI is associate with fine motor and visual motor integration deficits and confirmed anomalous temporal resolution in peripheral vision. Although we failed to find a more generalized visual perception impairment in motion and form perception, caution is needed in interpreting this result because of the small sample size.

Impact of Huntington's Disease on Mental Rotation Performance in Motor Pre-Symptomatic Individuals.

Huntington's disease (HD) is a genetic disorder known for affecting motor control. Despite evidence for the impact of HD on visual cortico-striatal loops, evidence for impaired visual perception in early symptomatic HD patients is limited; much less is known about what happens during the HD prodrome. The goals of this study were to evaluate perceptual processing in motor pre-manifest HD gene-carriers (Pre-HDs) during a visual mental rotation task. To achieve this goal, 79 participants including 24 Pre-HD participants and 55 healthy matched controls were scanned using functional MRI as they performed a mental rotation task. Another group of 36 subjects including 15 pre-HDs and 21 healthy age/gender matched controls participated in a control behavioral test of judgment of line orientation outside the scanner. We found that, although Pre-HDs (in this stage of disease) did not demonstrate slower response times, their response accuracy was lower than controls. On the fMRI task, controls showed a significant decrease in activity in the occipito-temporal (OT) visual network and increase in activity in the caudo-fronto-parietal (CFP) network with mental rotation load. Interestingly, the amount of mental rotation-related activity decrease in the OT network was reduced in Pre-HDs compared to controls while, the level of CFP response remained unchanged between the two groups. Comparing the link between the evoked BOLD activity within these networks and response accuracy (i.e., behavior), we found that the models fit to data from controls were less accurate in predicting response accuracy of Pre-HDs. These findings provide some of the earliest functional evidence of impaired visual processing and altered neural processing underlying visual perceptual decision making during the HD prodrome.

Assessing Environmental Safety Modifications in the Chronically Ill Sheltered Homeless: A Pilot Study

Abstract Date Presented 04/05/19 Cognitive problems, physical disabilities, and visual-perceptual impairment can heighten the risk of falls and other safety hazards in the chronically ill, sheltered homeless. This study demonstrated that environmental modifications and training may have contributed to the reduction of home safety events in a small group of prematurely aged, sheltered homeless. OT services are needed to help this underserved population remain safe and maintain housing once received. Primary Author and Speaker: Sharon Gutman Additional Authors and Speakers: Derek Douglas, Amber Carmiencke, Lauren Freudman, Maria Huerta, Matthew McCaa, Sam Miller, Alisha Sherpa, Miles Viant, Diane Schreibman

Assessment tool for visual perception deficits in cerebral visual impairment: reliability and validity.

To evaluate the reliability and validity of the Children's Visual Impairment Test for 3- to 6-year-olds (CVIT 3-6). Reliability was assessed via test-retest correlation and intraclass correlation coefficient (ICC) in typically developing children, children with cerebral visual impairment (CVI), intellectual impairment, and simulated impaired vision (validation groups n=59, mean developmental age=4y 10mo, 27 females, 32 males). Internal validity was evaluated with a confirmatory factor analysis on the normative sample (n=301, median age=4y 8mo,SD=9.7mo, 148 females, 153 males). External validity was assessed by correlating performance on CVIT 3-6 with L94, the Beery-Buktenica Developmental Test of Visuo-Motor Integration (Beery-VMI), the Freiburg Vision Test, the revised Snijders-Oomen Nonverbal Intelligence Test for children between 2years 6months and 7-years-old (SON-R 2.5-7), and the Social Responsiveness Scale (SRS) questionnaire and bycomparing performance between validation groups. We observed very good test-retest reliability (r=0.82, p<0.001, ICC=0.80) and confirmed the hypothesized factor structure (comparative fit index=1; Tucker-Lewis index=1.045). We found high correlations with tests with a strong visual perception component (L94: r=0.74, p<0.001; SON-R 2.5-7: r=0.37, p=0.01) and low correlations with other tests (Beery-VMI: r=0.25, p=0.09; SRS: r=0-0.26, p=0.09). Lowest scores were observed for children with CVIcompared to the other validation groups (F[3,44]=5.1, p=0.003). CVIT 3-6 is grounded in knowledge of visual perception. The tool specifically measures CVI-related visual perception deficits and is not mediated by intellectual abilities or low visual acuity. Evidence for good test-retest reliability of the Children's Visual Impairment Test for 3- to 6-year-olds (CVIT 3-6). Factor structure of normative data reflects CVIT 3-6's foundations in vision science. CVIT 3-6 specifically measures visual perception impairments. CVIT 3-6 performance is not influenced by intelligence or low visual acuity.

Clinical provision of compensatory visual training after neurological injury: example of a multisite outpatient program

Aim Treatment efficacy is established via controlled research trials, but treatment in real-world clinical environments is typically highly variable and may differ from research protocols by necessity. Here, we examined provision of visual retraining for adults after neurological injury at an outpatient rehabilitation program in Calgary, Canada. Methods Retrospective chart audits extracted demographic data, assessment outcomes, and details related to provision of training. Results Treatment was provided to individuals with both visual field and visual-perceptual impairments due to neurological injury (mostly stroke). Tools and techniques of visual retraining at this program are discussed, the common denominator being repetitive practice of compensatory visual behaviors. Across this multisite program, there was significant variability in the number of treatment sessions, 13.00 (±10.21) sessions for those with visual-perceptual impairments and 14.41 (±9.63) sessions for those with field loss. Descriptive statistics and confidence intervals suggest improved outcomes on some measures for those with visual field and visual perceptual impairments. Conclusions Our data suggest that visual retraining is feasible in this clinical outpatient setting. Implications for rehabilitation This program of visual retraining was provided to individuals with visual impairment (e.g., hemianopia) and visual perceptual impairment (e.g., unilateral spatial neglect) as a result of neurological injury. In this outpatient program, visual rehabilitation was feasible and appeared to improve outcomes among a heterogeneous clinical population. Fundamental characteristics of visual compensatory training at this program included repetitive practice of adaptive scanning behaviors across multiple contexts to promote automaticity and generalization of skills.

Development of Virtual Reality-based Visual Perception and Cognitive Rehabilitation Service

Purpose: Patients with brain damage suffer from limitations in performing the activities of daily living (ADL) because of their motor function and visual perception impairment. The aim of this study was to help improve the motor function and visual perception ability of patients with brain damage by providing them with virtual reality-based contents. The usability results of the patients and specialists group were also evaluated. Methods: The ADL contents consisted of living room, kitchen, veranda, and convenience store, similar to a real home environment, and these were organized by a rehabilitation specialist (e.g., neurologist, physiotherapist, and occupational therapist). The contents consisted of tasks, such as turning on the living room lights, organizing the drawers, organizing the kitchen, watering the plants on the veranda, and buying products at convenience stores. To evaluate the usability of the virtual reality-based visual cognitive rehabilitation service, general elderly subjects (n=11), stroke patients (n=7), stroke patients with visual impairment (n=4), and rehabilitation specialists (n=11) were selected. The questionnaires were distributed to the subjects who were using the service, and the subjective satisfaction of individual users was obtained as data. The data were analyzed using SPSS 21.0 software. The general characteristics of the users and the evaluation scores of the experts were analyzed using descriptive statistics. Results: The usability test result of this study showed that the mean value of the questionnaire related to content understanding and difficulty was high, between 4-5 points. Conclusion: The virtual reality rehabilitation service of this study is an efficient service that can improve the function, interest, and moti vation of stroke patients.

Lesions Responsible for Impaired Visual Perception in Poststroke Patients Using Voxel-Based Lesion Symptom Mapping.

We aimed to clarify the clinical characteristics that affect visual perception (VP) and elucidate lesion locations correlated with impaired VP. We reviewed 61 patients with stroke. Clinical assessments of a motor-free VP test were used to evaluate VP after stroke. Regression analyses were performed to examine predictors of impaired VP. We generated statistical maps of lesions related to impaired VP using voxel-based lesion symptom mapping (VLSM). The group of patients who had right hemispheric lesions had significantly low VP function. In a regression model, impaired VP was predicted by cognitive function, age, lesion volume, and right hemispheric lesion. Using VLSM, we found lesion location associated with impaired VP after adjusting for age, lesion volume, and Korean version of mini mental status exam. The results showed a lesion pattern with predominant distribution in the right parietal lobe and deep white matter. Age, lesion volume, and cognitive impairment affected the results of VP tests. Even after adjustments, we found that lesions responsible for impaired VP were located in the right parietal lobe and deep white matter. This result confirmed right hemispheric dominance for VP using VLSM. Clin. Anat. 32:689-696, 2019. © 2019 Wiley Periodicals, Inc.

Ventral and dorsal visual pathways exhibit abnormalities of static and dynamic connectivities, respectively, in patients with schizophrenia

Previous studies suggest that schizophrenia-related visual perceptual abnormalities are primarily attributed to deficits of the dorsal rather than ventral visual pathway. In this study, we comparatively explored changes in dorsal and ventral networks in schizophrenia patients in both static and dynamic functional connectivity (FC). Resting-state MR scans were acquired for forty schizophrenia patients and twenty-four healthy controls matched for age and gender. The dorsal and ventral visual networks were defined based on the resultant coordinates from activation likelihood estimation analyses. Static and dynamic network properties were calculated based on the full-range and segmented blood oxygen level dependent time series, respectively. The results indicated that the ventral and dorsal visual networks exhibited abnormalities in static FC and dynamic FC, respectively, in the schizophrenia group. Static FC assessments in the ventral visual network showed a significantly decreased clustering coefficient and shortened characteristic path length in patients with schizophrenia. Dynamic FC assessments in the dorsal visual network showed significantly higher mean temporal variability (p = 0.026) and higher regional FC variability of the right fusiform gyrus (p < 0.001) in patients with schizophrenia, and the latter was correlated with the total and negative scores of the Positive and Negative Syndrome Scale. In summary, this study reveals differential patterns of connectivity abnormalities of the ventral and dorsal visual networks in patients with schizophrenia. These preliminary evidences may help us better interpret the mechanisms underlying visual perceptual impairments in patients with schizophrenia and their relationship with psychosis.

Action Observation Therapy for Upper Extremity Motor Recovery in an Individual With Cognitive, Sensory, and Visual–Perceptual Deficits After Stroke

Abstract Date Presented 4/19/2018 Action observation therapy (AOT) is an effective upper extremity intervention for people with stroke; however, the benefits for those displaying multiple confounding impairments are unclear. This case study examined the use of AOT for an individual with sensory, cognitive, and visual–perceptual impairments after stroke. Primary Author and Speaker: Susanna Callender Contributing Authors: Lou DeMark

Vision impairment after traumatic brain injury: present knowledge and future directions.

Traumatic brain injury (TBI) is a major cause of mortality and morbidity in the USA as well as in the world. As a result of TBI, the visual system is also affected often causing complete or partial visual loss, which in turn affects the quality of life. It may also lead to ocular motor dysfunction, defective accommodation, and impaired visual perception. As a part of the therapeutic strategy, early rehabilitative optometric intervention is important. Orthoptic therapy, medication, stem cell therapy, motor and attention trainings are the available treatment options. Gene therapy is one of the most promising emerging strategies. Use of state-of-the-art nanomedicine approaches to deliver drug(s) and/or gene(s) might enhance the therapeutic efficacy of the present and future modalities. More research is needed in these fields to improve the outcome of this debilitating condition. This review focuses on different visual pathologies caused by TBI, advances in pre-clinical and clinical research, and available treatment options.

The characteristics of cortical activation during hand laterality task after ischemic stroke

Motor imagery (MI) has shown its effects as a neuro-rehabilitation strategy. But limited literature emphasized the neural mechanisms during MI in stroke patients. The purpose of this study is to investigate the features of cortical activation during the hand laterality task (HLT) using electroencephalogram (EEG) in stroke patients. Nine ischemic stroke patients and five age-matched control were recruited. EEG and behavior performances of subjects were recorded in the left/right hand judgement (HLT), which involves visual processing and mental rotation, and provides a good paradigm to study motor imagery and visual perception of hands. Reaction time (RT) and accuracy were used to evaluate the behavior performances; moreover, event-related potential (ERP) with the frequency from 0.5 to 40 Hz was analyzed to investigate the cortical activation. EEG and T1-weihted structural MRI (TR = 7.42 ms, TE = 3.26 ms) were incorporated to reveal the source activity of the cortex during the task. The RT is significantly longer in patient group than control, while the accuracy has no statistical difference between two groups ( Fig. 1 ). The ERP analysis showed that P200 (in parietal zone) and P300 (in central zone) amplitudes were significantly lower in stroke patients ( Fig. 2 ). Besides, source analysis shows the inactivation of the frontal lobe during P200 and bias activation during P300 when patients underwent this task. The manifestations of EEG signals during HLT in stroke patients indicated the impairments of visual perception and mental rotation related cognitive processes. It suggested that the underlying neural mechanisms of MI in time course and helped to optimize rehabilitation strategy.

Effects of Anodal Transcranial Direct Current Stimulation on Somatosensory Recovery After Stroke

The aim of this study was to evaluate the effect of anodal transcranial direct current stimulation over the primary somatosensory cortex on the recovery of somatosensation, motor function, and the activities of daily living in patients with subacute stroke. This study was a prospective, randomized sham controlled, double-blinded study. Patients with subacute stroke having somatosensory deficits (N = 24) were enrolled and assigned randomly to the anodal and sham stimulation groups. Patients received 10 consecutive anodal or sham transcranial direct current stimulations over the primary somatosensory cortex on the side of the stroke lesion. Before and after each stimulation session, Nottingham sensory assessments, Semmes Weinstein monofilaments examination, and manual function tests were performed, and modified Brunnstrom classification, modified Barthel index, and functional ambulation categories were assessed. Although there was no clear significant difference between the two groups, when the changes from baseline to posttreatment evaluation were compared between the groups, a partially significant improvement was observed in the anodal stimulation group compared with the sham stimulation group. Interestingly, the tactile sensation of the unaffected side also improved. Moreover, the greater improvement in activities of daily living function was observed in the anodal stimulation group too. Anodal transcranial direct current stimulation over the primary somatosensory cortex may be a useful adjuvant therapy for the recovery of somatosensation and activities of daily living function in patients with sensory deficits after stroke.

Aminergic neuromodulation of associative visual learning in harnessed honey bees.

The honey bee Apis mellifera is a major insect model for studying visual cognition. Free-flying honey bees learn to associate different visual cues with a sucrose reward and may deploy sophisticated cognitive strategies to this end. Yet, the neural bases of these capacities cannot be studied in flying insects. Conversely, immobilized bees are accessible to neurobiological investigation but training them to respond appetitively to visual stimuli paired with sucrose reward is difficult. Here we succeeded in coupling visual conditioning in harnessed bees with pharmacological analyses on the role of octopamine (OA), dopamine (DA) and serotonin (5-HT) in visual learning. We also studied if and how these biogenic amines modulate sucrose responsiveness and phototaxis behaviour as intact reward and visual perception are essential prerequisites for appetitive visual learning. Our results suggest that both octopaminergic and dopaminergic signaling mediate either the appetitive sucrose signaling or the association between color and sucrose reward in the bee brain. Enhancing and inhibiting serotonergic signaling both compromised learning performances, probably via an impairment of visual perception. We thus provide a first analysis of the role of aminergic signaling in visual learning and retention in the honey bee and discuss further research trends necessary to understand the neural bases of visual cognition in this insect.

Visual dependence affects postural sway responses to continuous visual field motion in individuals with cerebral palsy

ABSTRACTThe current study aimed to explore the impact of visual dependence on sensorimotor coupling of postural sway and visual motion in adults and teens with spastic cerebral palsy (CP). We hypothesized that individuals with CP would exhibit greater magnitudes of sway than healthy individuals, and the presence of visual dependence (VD) would produce instability in the direction of visual motion. Participants stood in a virtual environment in which the visual scene remained static or continuously rotated 30 degree/second in pitch-up or pitch-down. Increased center of pressure and center of mass responses were observed in the direction of visual scene motion in those with CP. Those with VD exhibited reduced frequency responses in anterior-posterior direction than those who were visually independent. VD suggests deficient sensorimotor integration that could contribute to postural instability and reduced motor function. Individuals with CP who are visually dependent may benefit from more sensory focused rehabilitation strategies.Abbreviations: AP, anterior-posterior; CP, cerebral palsy; COM, center of mass; COP, center of pressure; MDF, median frequency; ML, mediolateral; PD, pitch down (nose down) rotation; PU, pitch up (nose up) rotation; RFT, rod and frame test; RMS, root mean square; SLP, slope of the fitted line; TD, typical development; VD, visual dependence; VI, visual independence; VOR, vestibulo-ocular reflex; VPI, visual perceptual impairment

Face recognition impairment in small for gestational age and preterm children

BackgroundInfants born prematurely or with low birth weight are at increased risk of visual perceptual impairment. Face recognition is a high-order visual ability important for social development, which has been rarely assessed in premature or low birth weight children. AimsTo evaluate the influence of prematurity and low birth weight on face recognition skills. MethodsSeventy-seven children were evaluated as part of a prospective cohort study. They were divided into premature and term birth cohorts. Children with a birth weight below the 10th centile were considered small for gestational age. All children underwent a full ophthalmologic assessment and evaluation of face recognition skills using the Facial Memory subtest from the Test of Memory and Learning. ResultsPremature infants scored worse on immediate face recognition compared to term infants. However, after adjusting for birth weight, prematurity was not associated with worse outcomes. Independent of gestational age, outcomes of low birth weight children were worse than those of appropriate birth weight children, for immediate face recognition (odds ratio [OR], 5.14; 95% confidence interval [CI], 1.32–21.74) and for face memory (OR, 4.48; 95% CI, 1.14–16.95). ConclusionsBeing born small for gestational age is associated with suboptimal face recognition skills, even in children without major neurodevelopmental problems.

Reduced intrinsic visual cortical connectivity is associated with impaired perceptual closure in schizophrenia.

Sensory perceptual processing deficits, such as impaired visual object identification and perceptual closure, have been reported in schizophrenia. These perceptual impairments may be associated with neural deficits in visual association areas, including lateral occipital cortex and inferior temporal areas. However, it remains unknown if such deficits can be found in the intrinsic architecture of the visual system.In the current study, we measured perceptual closure performance and resting-state functional connectivity using functional magnetic resonance imaging (FMRI) in 16 schizophrenia patients and 16 matched healthy controls. We estimated intrinsic functional connectivity using self-organized grouping spatial ICA, which clusters component maps in the subject space according to spatial similarity. Patients performed worse than controls in the perceptual closure task. This impaired closure performance of patients was correlated with increased severity of psychotic symptoms. We also found that intrinsic connectivity of the visual processing system was diminished in patients compared to controls. Lower perceptual closure performance was correlated to lower visual cortical intrinsic connectivity overall.We suggest that schizophrenia is associated with impaired intrinsic connectivity of the visual system, and that it is a potential mechanism leading to impaired visual object perception. These findings contribute to increasing evidence for impairments of higher visual functions in schizophrenia.

Famous faces and voices: Differential profiles in early right and left semantic dementia and in Alzheimer's disease

BackgroundFamous face and voice recognition is reported to be impaired both in semantic dementia (SD) and in Alzheimer's Disease (AD), although more severely in the former. In AD a coexistence of perceptual impairment in face and voice processing has also been reported and this could contribute to the altered performance in complex semantic tasks. On the other hand, in SD both face and voice recognition disorders could be related to the prevalence of atrophy in the right temporal lobe (RTL). ObjectiveThe aim of the present study was twofold: (1) to investigate famous faces and voices recognition in SD and AD to verify if the two diseases show a differential pattern of impairment, resulting from disruption of different cognitive mechanisms; (2) to check if face and voice recognition disorders prevail in patients with atrophy mainly affecting the RTL. MaterialsTo avoid the potential influence of primary perceptual problems in face and voice recognition, a pool of patients suffering from early SD and AD were administered a detailed set of tests exploring face and voice perception. Thirteen SD (8 with prevalence of right and 5 with prevalence of left temporal atrophy) and 25 CE patients, who did not show visual and auditory perceptual impairment, were finally selected and were administered an experimental battery exploring famous face and voice recognition and naming. Twelve SD patients underwent cerebral PET imaging and were classified in right and left SD according to the onset modality and to the prevalent decrease in FDG uptake in right or left temporal lobe respectively. Correlation of PET imaging and famous face and voice recognition was performed. ResultsResults showed a differential performance profile in the two diseases, because AD patients were significantly impaired in the naming tests, but showed preserved recognition, whereas SD patients were profoundly impaired both in naming and in recognition of famous faces and voices. Furthermore, face and voice recognition disorders prevailed in SD patients with RTL atrophy, who also showed a conceptual impairment on the Pyramids and Palm Trees test more important in the pictorial than in the verbal modality.Finally, in 12SD patients in whom PET was available, a strong correlation between FDG uptake and face-to-name and voice-to-name matching data was found in the right but not in the left temporal lobe. DiscussionThe data support the hypothesis of a different cognitive basis for impairment of face and voice recognition in the two dementias and suggest that the pattern of impairment in SD may be due to a loss of semantic representations, while a defect of semantic control, with impaired naming and preserved recognition might be hypothesized in AD. Furthermore, the correlation between face and voice recognition disorders and RTL damage are consistent with the hypothesis assuming that in the RTL person-specific knowledge may be mainly based upon non-verbal representations.

Impaired perception of human movements in Parkinson’s disease

Interacting with other individuals in a social world requires fast and accurate perception of other individuals’ identity, actions, or intentions. Humans are very efficient in these social tasks, as they can extract social information even if the actor is represented only by a handful of point-lights on an otherwise invisible body. Theories have argued that efficient visual perception of actions is based on intact motor system functioning. The motor system provides visuo-motor action representations shaped by the observer’s own movements or motor repertoire. If the observer’s motor repertoire is impaired, this should lead to impaired visuo-motor representations and ultimately to impaired visual perception of movements. Here we tested this hypothesis in a behavioral study with patients suffering from Parkinson’s disease (PD). PD patients are typically impaired in movement execution. We tested these patients and a matched control group in a visual discrimination task on human movement perception. The results showed that PD patients were significantly impaired in the perception of human movements. This impairment was most prominent for transitive (object-related) movements. The results indicate that impaired movement execution critically influences movement perception. The results support the hypothesis that the motor system plays a causal role for the visual perception of human movements.

Predictors of non-vertebral fracture in older Chinese males and females: Mr. OS and Ms. OS (Hong Kong).

Clinical risk factors to predict fracture are useful in guiding management of patients with osteoporosis or falls. Clinical predictors may however be population specific because of differences in lifestyle, environment and ethnicity. Four thousand community-dwelling Chinese males and females with average ages of 72.4 and 72.6years were followed up for incident fractures, with an average of 6.5 and 8.8years, respectively. Clinical information was collected, and bone mineral density (BMD) measurements were carried out at baseline. Stepwise Cox regression models were used to identify risk factors of nonvertebral fractures, with BMD as covariate. Areas under the receiver-operating characteristic (ROC) curve (AUC) were compared among different risk models. The incidence rates of nonvertebral fractures were 10.3 and 20.5 per 1000 person years in males and females, respectively. In males, age ≥80, history of a fall in the past year, fracture history, chronic obstructive pulmonary disease, impaired visual depth perception and low physical health-related quality of life were significant fracture risk factors, independent of BMD. In females, the significant factors were fracture history, low visual acuity and slow narrow walking speed. The clinical risk factors had a significant influence on fracture risk irrespective of osteoporosis status, even having a better risk discrimination than BMD alone, especially in males. The best risk prediction model consisted both BMD and clinical risk factors. Clinical risk factors have additive value to hip BMD in predicting nonvertebral fractures in older Chinese people and may predict them better than BMD alone in older Chinese males.