Cost and benefit of parafoveal information during reading acquisition as revealed by finger movement patterns.

Contrary to expert readers, children learning to read have limited ability to preprocess letters in parafoveal vision. Parafoveal letters induce crowding cost: the features of neighboring letters interfere with target letter identification. We longitudinally studied the weight of parafoveal cost and benefit in two group of children (N = 42), during their first school year (Group 1) and at the end of second school year (Groupe 2). Using a novel digit-tracking method, a blurred text was presented and rendered unblurred by touching the screen, allowing the user to discover a window of visible text as the finger moved along it. We compared two conditions: (1) a large window, where crowding was enhanced by the presence of parafoveal information; (2) a small window, where crowding was suppressed by blurred parafoveal information. Finger kinematics were simultaneously recorded. We found that at the beginning of first-grade, digital fixations - brief slowing or stopping of the finger on a specific point - are significantly longer in the large compared to the small window condition, as parafoveal crowding increases text processing difficulty. This effect diminishes and disappears at the end of second-grade as reading performance improves. In the large window condition, longer digital saccades - rapid movements of the finger changing position - appear by the end of first grade suggesting that parafoveal exposure become more beneficial than harmful when children acquire basic reading skills. Our results show that in beginning readers, crowding has a cognitive cost that interfere with the speed of the learning reading process. Our findings are relevant to the field of education by showing that visual crowding in first grade should not be underestimated.

Assessing the allocation of attention during visual search using digit-tracking, a calibration-free alternative to eye tracking.

Digit-tracking, a simple, calibration-free technique, has proven to be a good alternative to eye tracking in vision science. Participants view stimuli superimposed by Gaussian blur on a touchscreen interface and slide a finger across the display to locally sharpen an area the size of the foveal region just at the finger's position. Finger movements are recorded as an indicator of eye movements and attentional focus. Because of its simplicity and portability, this system has many potential applications in basic and applied research. Here we used digit-tracking to investigate visual search and replicated several known effects observed using different types of search arrays. Exploration patterns measured with digit-tracking during visual search of natural scenes were comparable to those previously reported for eye-tracking and constrained by similar saliency. Therefore, our results provide further evidence for the validity and relevance of digit-tracking for basic and applied research on vision and attention.

[Subacute cerebellar ataxia, an uncommon SARS-CoV-2 complication infection in older adults]. / Ataxie cérébelleuse subaiguë : une atteinte atypique par le SARS-CoV-2 chez la personne âgée.

Cerebellar ataxia can be caused by neoplasia, toxics (drugs, heavy metals, alcohol), infection, vascular lesions or auto-immune and paraneoplastic pathologies. Neuroimaging must be performed urgently in case of sudden onset and serologies as well as a lumbar puncture should be performed. Several case reports of ataxia associated with COVID-19 have been published, however the underlying pathogenic mechanisms remain unclear. This is a diagnosis of exclusion when other causes are ruled out and when the ataxia appears simultaneously to COVID-19 infection. We lack data on best management, but the prognosis appears mostly favorable with good functional recovery without any specific treatment. This paper describes the case of a patient who developed a cerebellar ataxia as the only neurological manifestation of a SARS-CoV-2 infection.

Une ataxie cérébelleuse peut être causée par un processus (para)néoplasique, auto-imun, une exposition toxique, une infection ou une lésion vasculaire. Une imagerie doit être réalisée en urgence devant toute atteinte aiguë et le bilan devrait être complété par des sérologies larges et une ponction lombaire. Plusieurs cas d'ataxie liée au Covid-19 ont été décrits, dont le mécanisme étiopathogénique reste incomplètement élucidé, le diagnostic se faisant plutôt par exclusion lorsque les symptômes apparaissent de manière concomitante à l'infection. Des données manquent sur la prise en charge mais le pronostic semble favorable, avec une bonne récupération fonctionnelle. Cet article décrit le cas d'une patiente ayant présenté une ataxie cérébelleuse comme symptôme neurologique isolé contemporain d'une infection à SARS-CoV-2.

Ability of quantitative PCR to discriminate Pneumocystis jirovecii pneumonia from colonization.

Introduction. Pneumocystis jirovecii pneumonia (PCP) is a severe disease affecting immunocompromised patients. Diagnosis is difficult due to the low sensitivity of direct examination and inability to grow the pathogen in culture. Quantitative PCR in bronchoalveolar lavage fluid (BAL) has high sensitivity, but limited specificity for distinguishing PCP from colonization.Aim. To assess the performance of an in-house quantitative PCR to discriminate between PCP and colonization.Methodology. This was a single-centre retrospective study including all patients with a positive PCR result for P. jirovecii in BAL between 2009 and 2017. Irrespective of PCR results, PCP was defined as the presence of host factors and clinical/radiological criteria consistent with PCP and (i) the presence of asci at direct examination of respiratory sample or (ii) anti-PCP treatment initiated with clinical response and absence of alternative diagnosis. Colonization was considered for cases who did not receive anti-PCP therapy with a favourable outcome or an alternative diagnosis. Cases who did not meet the above mentioned criteria were classified as 'undetermined'.Results. Seventy-one patients with positive P. jirovecii PCR were included (90 % non-HIV patients). Cases were classified as follows: 37 PCP, 22 colonization and 12 undetermined. Quantitative PCR values in BAL were significantly higher in patients with PCP versus colonization or undetermined (P<0.0001). The cut-off of 5×103 copies/ml was able to discriminate PCP cases from colonization with 97 % sensitivity, 82 % specificity, 90 % positive predictive value and 95 % negative predictive value.Conclusions. Our quantitative PCR for P. jirovecii in BAL was reliable to distinguish PCP cases from colonization in this predominantly non-HIV population.

Reduced CMRO2 and cerebrovascular reserve in patients with severe intracranial arterial stenosis: a combined multiparametric qBOLD oxygenation and BOLD fMRI study.

Multiparametric quantitative blood oxygenation level dependent (mqBOLD) magnetic resonance Imaging (MRI) approach allows mapping tissular oxygen saturation (StO2 ) and cerebral metabolic rate of oxygen (CMRO2 ). To identify hemodynamic alteration related to severe intracranial arterial stenosis (SIAS), functional MRI of cerebrovascular reserve (CVR BOLD fMRI) to hypercapnia has been proposed. Diffusion imaging suggests chronic low grade ischemia in patients with impaired CVR. The aim of the present study was to evaluate how oxygen parameters (StO2 and CMRO2 ), assessed with mqBOLD approach, correlate with CVR in patients (n = 12) with SIAS and without arterial occlusion. The perfusion (dynamic susceptibility contrast), oxygenation, and CVR were compared. The MRI protocol conducted at 3T lasted approximately 1 h. Regions of interest measures on maps were delineated on segmented gray matter (GM) of middle cerebral artery territories. We have shown that decreased CVR is spatially associated with decreased CMRO2 in GM of patients with SIAS. Further, the degree of ipsilateral CVR reduction was well-correlated with the amplitude of the CMRO2 deficit. The altered CMRO2 suggests the presence of a moderate ischemia explained by both a decrease in perfusion and in CVR. CVR and mqBOLD method may be helpful in the selection of patients with SIAS to advocate for medical therapy or percutaneous transluminal angioplasty-stenting.

DnaK prevents human insulin amyloid fiber formation on hydrophobic surfaces.

We have developed a multiwell-based protein aggregation assay to study the kinetics of insulin adsorption and aggregation on hydrophobic surfaces and to investigate the molecular mechanisms involved. Protein-surface interaction progresses in two phases: (1) a lag phase during which proteins adsorb and prefibrillar aggregates form on the material surface and (2) a growth phase during which amyloid fibers form and then are progressively released into solution. We studied the effect of three bacterial chaperones, DnaK, DnaJ, and ClpB, on insulin aggregation kinetics. In the presence of ATP, the simultaneous presence of DnaK, DnaJ, and ClpB allows good protection of insulin against aggregation. In the absence of ATP, DnaK alone is able to prevent insulin aggregation. Furthermore, DnaK binds to insulin adsorbed on hydrophobic surfaces. This process is slowed in the presence of ATP and can be enhanced by the cochaperone DnaJ. The peptide LVEALYL, derived from the insulin B chain, is known to promote fast aggregation in a concentration- and pH-dependent manner in solution. We show that it also shortens the lag phase for insulin aggregation on hydrophobic surfaces. As this peptide is also a known DnaK substrate, our data indicate that the peptide and the chaperone might compete for a common site during the process of insulin aggregation on hydrophobic surfaces.