Stimulus contrast, pursuit mode, and age strongly influence tracking performance on a continuous visual tracking task.

Human observers tend to naturally track moving stimuli. This tendency may be exploited towards an intuitive means of screening visual function as an impairment induced reduction in stimulus visibility will decrease tracking performance. Yet, to be able to detect subtle impairments, stimulus contrast is critical. If too high, the decrease in performance may remain undetected. Therefore, for this approach to become reliable and sensitive, we need a detailed understanding of how age, stimulus contrast, and the type of stimulus movement affect continuous tracking performance. To do so, we evaluated how well twenty younger and twenty older participants tracked a semi-randomly moving stimulus (Goldmann size III, 0.43 degrees of visual angle), presented at five contrast levels (5%-10%-20%-40%-80%). The stimulus could move smoothly only (smooth pursuit mode) or in alternation with displacements (saccadic pursuit mode). Additionally, we assessed static foveal and peripheral contrast thresholds. For all participants, tracking performance improved with increasing contrast in both pursuit modes. To reach threshold performance levels, older participants required about twice as much contrast (20% vs. 10% and 40% vs. 20% in smooth and saccadic modes respectively). Saccadic pursuit detection thresholds correlated significantly with static peripheral contrast thresholds (rho = 0.64). Smooth pursuit detection thresholds were uncorrelated with static foveal contrast thresholds (rho = 0.29). We conclude that continuous visual stimulus tracking is strongly affected by stimulus contrast, pursuit mode, and age. This provides essential insights that can be applied towards new and intuitive approaches of screening visual function.

Measuring saccades in patients with Niemann-Pick type C: A comparison between video-oculography and a novel eye tracking test based on continuous psychophysics.

Introduction: Vertical supranuclear gaze palsy is a key feature of Niemann-Pick type C (NP-C) and is commonly quantified using video-oculography (VOG). VOG requires sitting still for long times and performing specific tasks, thus it can be challenging or impossible for patients severely affected by movement disorders or cognitive impairment. To overcome this limitation, we measure saccades of NP-C patients using a fast eye tracking test based on continuous psychophysics and compare it to VOG. Methods: Saccades of six NP-C patients and six age-matched controls were assessed using VOG and Standardized Oculomotor and Neuro-ophthalmic Disorders Assessment (SONDA). In SONDA, participants continuously track a semi-randomly moving dot on a computer screen while their gaze is being tracked. For both assessments, saccades were quantified using four conventional measures: amplitude, gain, latency, and peak velocity. Furthermore, SONDA's continuous measures were quantified with several novel spatio-temporal properties. Results: In the NP-C patients, both methods revealed reduced amplitude, gain, peak velocity, and increased latency of vertical saccades compared to horizontal saccades and compared to healthy controls. Effect sizes obtained with SONDA were overall larger than those for VOG. SONDA's spatio-temporal properties showed similar trends. Conclusion: SONDA reveals a deterioration of vertical saccades in NP-C patients that is consistent with VOG. SONDA's measures based on continuous psychophysics are consistent with traditional saccadic parameters and can potentially provide complementary information. SONDA shows larger effect sizes than VOG, suggesting that it provides robust and clinically relevant outcomes with a more intuitive task and shorter testing time.

Microstructural Visual Pathway White Matter Alterations in Primary Open-Angle Glaucoma: A Neurite Orientation Dispersion and Density Imaging Study.

BACKGROUND AND PURPOSE: DTI studies of patients with primary open-angle glaucoma have demonstrated that glaucomatous degeneration is not confined to the retina but involves the entire visual pathway. Due to the lack of direct biologic interpretation of DTI parameters, the structural nature of this degeneration is still poorly understood. We used neurite orientation dispersion and density imaging (NODDI) to characterize the microstructural changes in the pregeniculate optic tracts and the postgeniculate optic radiations of patients with primary open-angle glaucoma, to better understand the mechanisms underlying these changes. MATERIALS AND METHODS: T1- and multishell diffusion-weighted scans were obtained from 23 patients with primary open-angle glaucoma and 29 controls. NODDI parametric maps were produced from the diffusion-weighted scans, and probabilistic tractography was used to track the optic tracts and optic radiations. NODDI parameters were computed for the tracked pathways, and the measures were compared between both groups. The retinal nerve fiber layer thickness and visual field loss were assessed for the patients with glaucoma. RESULTS: The optic tracts of the patients with glaucoma showed a higher orientation dispersion index and a lower neurite density index compared with the controls (P < .001 and P = .001, respectively), while their optic radiations showed a higher orientation dispersion index only (P = .003). CONCLUSIONS: The pregeniculate visual pathways of the patients with primary open-angle glaucoma exhibited a loss of both axonal coherence and density, while the postgeniculate pathways exhibited a loss of axonal coherence only. Further longitudinal studies are needed to assess the progression of NODDI alterations in the visual pathways of patients with primary open-angle glaucoma across time.

The Birthday Party Test (BPT): A new picture description test to support the assessment of simultanagnosia in patients with acquired brain injury.

There is broad consensus on the utility of complex pictures in the assessment of simultanagnosia in patients with acquired brain injury (ABI). To overcome various shortcomings of current instruments, we have developed the Birthday Party Test (BPT); a picture description test that contains a neutral scene, a balanced representation of events, and provides clear instructions and a scoring-aid. We have applied the BPT in a large group of patients with ABI (n = 502) and in an age-matched healthy control group (n = 194). Our results show that performance on the BPT was associated with a range of descriptive, neuropsychological and clinical characteristics and that poor test performance appeared to be more common in patients with etiologies that have an increased risk of bilateral damage. Furthermore, we assume a high correspondence between test performance on the BPT and the assessor's clinical judgment of likely having simultanagnosia in preliminary analyses. This study shows the potential usefulness of the BPT to support diagnostic decision making in simultanagnosia. The BPT is made freely available to facilitate its broad application in the clinical assessment of patients with visual impairment and to enable a further evaluation of its utility and validity in future studies.

Visual hallucinations in psychosis.

The Dutch version of the Visual Hallucination Questionnaire was used to assess lifetime visual hallucinations (VH) characteristics in 27 patients with psychosis. Our results confirmed substantial variance in many VH characteristics. Most patients reported multiple VH types. Complex VH were most prevalent, mainly consisting of people and animals, followed by simple, then geometric VH. Few patients experienced only simple VH. The VH generally had features resembling real perceptions. Insight was usually reduced. VH ranged from 'appropriate' and neutral to peculiar and delusion-associated. VH accompanied by fright and sound seem to be related to experiencing complex or multiple types of VH.

Screening of visual perceptual disorders following acquired brain injury: A Delphi study.

Impairments in visual perception are common after acquired brain injury (ABI) and adequate assessment is crucial for diagnosis and rehabilitation. However, there is no consensus yet on how to assess these disorders after ABI. The aim of the present study was to explore what measures are considered reasonable to be part of a test battery for the screening of a broad range of mid-level and higher-order visual perceptual disorders. A Delphi method was used to collect the opinions of 28 international multidisciplinary experts in visual perception in order to achieve consensus on the content of the test battery. Seventeen experts evaluated the test battery proposed in the third and final round of the Delphi process. Consensus was achieved (94%) on a battery of 11 distinctive tests with an expected administration time of 30 minutes. The current study provides an essential step in the development of a standardized and time-efficient test battery for the screening of mid-level and higher-order visual perceptual disorders. The composed battery may improve effectiveness of clinical assessment by providing insight into potential visual deficits in little time, thereby initiating further assessment. Future studies should focus on the validation of the suggested test battery and collect normative data.

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

BACKGROUND: 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. METHOD: 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. RESULTS: 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. CONCLUSIONS: 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'.

[Survival and mortality in ESRD patients]. / Survie et mortalité des patients en IRCT.

This chapter provides a set of indicators on survival, life expectancy and causes of death of patients in chronic renal failure treated by dialysis or transplantation beginning a first replacement therapy between 2002 and 2011. Age strongly influences survival on dialysis. Thus, one year survival of patients under age 65 is over 90%. After 5 years, among patients over 85 years, it is more than 15%. The presence of diabetes or one or more cardiovascular comorbidities also significantly worse patient survival. In terms of trend, we do not find significant improvement in the 2-year survival between patients in the cohort 2006-2007 and the 2008-2009 cohort. Cardiovascular diseases account for 27% of causes of death to infectious diseases (12%) and cancer (10%). Life expectancy of patients is highly dependent on their treatment. Thus, a transplant patient aged 30 has a life expectancy of 41 years versus 23 years for a dialysis patient. Transplant patients have a mortality rate much lower than those of dialysis patients. Thus, between 60 and 69 years, for 1000 patients in dialysis in 2011, 127 died within the year. For 1000 patients of the same age, who have a functioning kidney transplant, 24 died within the year.

[Access to the waiting list and renal transplantation]. / Accès à la liste d'attente et à la greffe rénale.

This chapter provides a set of indicators related to Renal Transplantation access in France. It describes patient outcomes and reports on cumulative incidence rates of wait-listing and renal transplantation according to main patient of characteristics and regions. The REIN registry integrates kidney transplant and dialysis data. It provides a comprehensive view on waiting list and renal transplantation access to the patients, nephrologists, and national or regional health authorities. Access to the waiting list is evaluated on a cohort of 51,845 new patients who started dialysis between 2002 and 2011 in 25 regions. The probability of first wait-listing was of 3.7% at the start of dialysis (pre-emptive registrations), 15% at 12, 22% at 36 and 24% to 60 months. The probability of being registered was strongly related to age, diabetes and region. Patient older than 60 had a very poor access to the waiting list, whatever their diabetes status was. Probability of first wait-listing was much lower (36.5% at 60 months) in type 2 diabetic-40 to 59 years old patients. Among 13,653 patients less than 60 years old, the probability of being registered was 11% at the start of dialysis, 43% to 12 months, 62% to 36 months and 66% to 60 months (median dialysis duration: 16 months). Seventeen regions with up to 5 years follow-up show an increase of 8 to 15% in pre-emptive registrations between 2007 and 2001, without change at 1 year. Access to kidney transplant is evaluated on a cohort of 53,301 new patients who started a renal replacement therapy (dialysis or pre-emptive renal transplant) between 2002 and 2011 in 25 regions. The probability of first kidney transplant was of 7% at 12, 17% at 36 and 21% at 60 months. 8,633 patients (16,2%) had received a first renal transplant within 14.7 month median time; 1,455 (2.7%) had received a pre-emptive graft [male: 58%, median age: 48.7y]. Among the 14,770 new patients less than 60 years old, the probability of being transplanted was of 21% at 12, 46% at 36 and 58% at 60 months (median dialysis duration: 42 months). When pre-emptive graft were excluded, the probability of being transplanted was of 5% at 12, 15% to 36 and 19% to 60 months Insofar as kidney transplant is regarded as the most efficient treatment, access to the waiting list and renal transplant are sensitive issues.

Models as instruments for optimizing hospital processes: a systematic review.

PURPOSE: The purpose of this article is to find decision-making models for the design and control of processes regarding patient flows, considering various problem types, and to find out how usable these models are for managerial decision making. DESIGN/METHODOLOGY/APPROACH: A systematic review of the literature was carried out. Relevant literature from three databases was selected based on inclusion and exclusion criteria and the results were analyzed. FINDINGS: A total of 68 articles were selected. Of these, 31 contained computer simulation models, ten contained descriptive models, and 27 contained analytical models. The review showed that descriptive models are only applied to process design problems, and that analytical and computer simulation models are applied to all types of problems to approximately the same extent. Only a few models have been validated in practice, and it seems that most models are not used for their intended purpose: to support management in decision making. RESEARCH LIMITATIONS/IMPLICATIONS: The comparability of the relevant databases appears to be limited and there is an insufficient number of suitable keywords and MeSH headings, which makes searching systematically within the broad field of health care management relatively hard to accomplish. PRACTICAL IMPLICATIONS: The findings give managers insight into the characteristics of various types of decision-support models and into the kinds of situations in which they are used. ORIGINALITY/VALUE: This is the first time literature on various kinds of models for supporting managerial decision making in hospitals has been systematically collected and assessed.

Judging relative positions across saccades.

When components of a shape are presented asynchronously during smooth pursuit, the retinal image determines the perceived shape, as if the parts belong to the moving object that the eyes are pursuing. Saccades normally shift our gaze between structures of interest, so there is no reason to expect anything to have moved with the eyes. We therefore decided to examine how people judge the separation between a target flashed before and another flashed after a saccade. Subjects tracked a jumping dot with their eyes. Targets were flashed at predetermined retinal positions, with a 67-242 ms interval between the flashes. After each trial subjects indicated where they had seen the targets. We selected the trials on which subjects made a complete saccade between the presentations of the two targets. For short inter-target intervals, subjects' judgements depended almost exclusively on the retinal separation, even when there were conspicuous visual references nearby. Even for the longest intervals, only part of the change in eye orientation was taken into consideration. These findings cannot simply be accounted for on the basis of the mislocalisation of individual targets or a compression of space near saccades. We conclude that the retinal separation determines the perceived separation between targets presented with a short interval between them, irrespective of any intervening eye movements.

Evidence of enhancement of spatial attention during inhibition of a visuo-motor response.

A visuo-motor task was used as the setting for a study into inhibition in six healthy volunteers using fMRI. The task involved responding to colored stimuli, which appeared at random positions in the left and right visual field, with the corresponding hand. The volunteers were asked to respond to green colored stimuli ("go" response) and to inhibit responses to red stimuli ("no-go" response). The task was presented in a block design with blocks of three types; only "go" trials, a pseudo-random mixture of "go" and "no-go" tasks ("go/no-go" block), and "visual control." ANCOVA analysis of the fMRI data was performed within the framework of SPM99. Increased activation in the go vs visual control comparison was found in the bilateral motor and medial premotor cortices associated with the action of the button press response, as well as parietal regions attending to the task of identifying the visual field. The go/no-go vs visual control comparison showed a similar pattern, plus additional prefrontal areas that have previously been shown to be associated with inhibition. The direct comparison of the go and go/no-go blocks highlighted large differences not only in the prefrontal cortices, associated with inhibition, but also particularly in the right parietal cortex. We interpret the increased parietal activation, during inhibition, as representing a heightened spatial attention required for the correct execution of the inhibition task.

Hemianopic visual field defects elicit hemianopic scanning.

Previous explanations for the variability in success of compensating for homonymous hemianopia (HH) has been in terms of extent of the brain injury. In using on-line eye movement registrations, we simulated HH in 16 healthy subjects and compared their scanning performance on a dot counting task to their own "normal" condition and to real HH patients' performance. We evidenced clear parallels between simulated and real HH, suggesting that hemianopic scanning behaviour is primarily visually elicited, namely by the visual field defect, and not by the additional brain damage. We further observed age-related processes in compensating for the HH.

Grey scales uncover similar attentional effects in homonymous hemianopia and visual hemi-neglect.

Multi-component models of visual hemi-neglect have postulated that visual hemi-neglect is characterised by various attentional deficits. A grey scales task has been developed to quantify the early, automatic, (perhaps obligatory) ipsilesional orienting of visual attention, frequently assumed as the first of these attentional deficits. Explanations for this attentional imbalance are up until now mainly formulated in terms of right hemisphere activation. This lateral attentional bias has also been demonstrated in controls, in whom it is expressed as a leftward perceptual asymmetry. We reproduced previous literature findings on a grey scales task, considering controls and neglect patients. Three patients with neglect showed an extreme ipsilesional lateral bias. This bias did not change during or after cognitive rehabilitation. Additionally, we presented this grey scale task to 32 patients with left- and right-sided homonymous hemianopia (HP). HP is the loss of sight in one visual hemi-field. The HH patients had no clinical signs of impaired lateralised attention. Results revealed that HH patients showed a similar ipsilesional bias, albeit to a lesser degree than in neglect. Left-sided HH patients presented a quantitatively similar, but qualitatively opposite bias than the right-sided HH patients. We suggest that sensory effects can be an alternative source of attentional imbalance, which can interact with the previously proposed (right) hemispheric effects. This suggests that the perceptual asymmetry in the grey scales task is not necessarily an indicator of impaired right hemisphere attention. It rather suggests a pattern of functional cerebral asymmetry, which can also be caused by asymmetric sensory input.

The focal adhesion targeting sequence is the major inhibitory moiety of Fak-related non-kinase.

Focal adhesion kinase (FAK) plays an important role in integrin-mediated signal transduction pathways and its C-terminal noncatalytic domain Fak-related non-kinase (FRNK), which is autonomously expressed, acts as an inhibitor of FAK. A model has been proposed where FAK and FRNK compete for an essential common binding protein. A FRNK variant in which the direct interaction with v-Crk-associated tyrosine kinase substrate (CAS) was disturbed by point mutations still functioned as an inhibitor of FAK, suggesting that FRNK is unlikely to inhibit FAK by sequestering CAS. Deletion variants of FRNK within the region N-terminal to the focal adhesion targeting (FAT) sequence were still able to inhibit FAK function, indicating that this region is dispensable for the inhibitory effect of FRNK. Overexpression of a green fluorescent protein (GFP) fusion protein containing the FAT sequence delayed cell spreading and reduced FAK tyrosine phosphorylation. This indicates that the FAT sequence is the major inhibitory moiety within FRNK.

A girl without a chiasm: electrophysiologic and MRI evidence for the absence of crossing optic nerve fibers in a girl with a congenital nystagmus.

An otherwise healthy 15-year-old girl with a congenital nystagmus was evaluated at our department using visual evoked potential recording and magnetic resonance imaging. She appears to have the unique isolated inborn absence of the optic chiasm, described only once before in two unrelated girls. Unlike these previously described cases, our patient does not seem to display a see-saw nystagmus.

Separate simultaneous processing of egocentric and relative positions.

It is well established that all kinds of visual attributes are processed separately within the brain. This separation is related to differences in the information that is relevant for the different attributes. When attributes differ greatly (such as colour and motion) it is obvious that they must rely on different information. However, separating the processing of different attributes could also allow highly related attributes to evolve independently, so that they end up being judged on the basis of different types of information. Here, we examine the case of egocentric and relative localisation. For judging egocentric positions, the orientation of the eyes has to be taken into account. This is not so for judging relative positions. We demonstrate that these two attributes can be processed separately by showing that simultaneous judgements of relative and egocentric position differ in their dependency on eye orientation. Subjects pursued a moving dot. We flashed either single targets, or pairs of targets with a 67 ms interval between them, directly below the subjects' gaze. As the eyes were moving during the 67 ms interval, the retinal separation between pairs of targets was different from their actual separation. Subjects indicated the position at which they saw the targets with reasonable reproducibility, with a consistent bias in the direction of the eye movement. However, when two targets were flashed, the indicated separation between them usually coincided with their retinal separation, rather than with their actual separation. We conclude that egocentric and relative spatial positions can be estimated separately and simultaneously, on the basis of different types of information.

Visual memory for random block patterns defined by luminance and color contrast.

We studied the ability of human subjects to memorize the visual information in computer-generated random block patterns defined either by luminance contrast, by color contrast, or by both. Memory performance declines rapidly with increasing inter-stimulus interval, showing a half-life of approximately 3 s. We further show that memory performance declines with eccentricity approximately as a Gaussian function of position. Memory decay functions did not depend on whether the patterns were defined by luminance or color contrast. Changing both luminance and color components of block patterns in conjunction did not improve performance suggesting a single memory mechanism is used to store luminance and color derived pattern information. Our results further suggest that color identity (hue, saturation) and pattern information extracted from color- or luminance-contrast are stored independently of each other.