Recherche translationnelle: de l'animal modèle de schizophrénie à la forme humaine de difficulté cognitive. Evaluation des performances de navigation spatiale et des stratégies utilisées

Un protocole de tests sur labyrinthe radial permettant d'évaluer la navigation spatial chez l'homme a été réalisé. Ces tests sur labyrinthe radial sont basés sur le protocole utilisé sur l'animal modèle de schizophrénie dans le CNP (Centre de neuroscience psychiatrique) de Lausanne. Les recherches actuelles du CNP ont montré un déficit dans les capacités d'orientation spatiale de ces animaux [13]. Ainsi notre méthodologie consistera à tester des sujets humains dans des tâches de labyrinthe afin d'étudier de la manière la plus équivalente les différents déficits observés dans la pathologie humaine et dans le rat modèle. Cette démarche est à la base d'une approche translationnelle qui combine recherches cliniques et expérimentales. Le travail expérimental a été mené sur deux dispositifs analogues. a) «radial au doigt», ensemble de petits canaux qui peuvent être explorés par le doigt, yeux ouverts ou fermés et dans lesquels des textures différentes tapissent chaque bras. b) «radial sur écran tactile», deux labyrinthes qui comparent deux types d'indice locale, couleurs différentes ou patrons noir-blanc. Dans les deux dispositifs a été prévu une série de tests permettant d'évaluer la mémorisation des indices utilisés en les supprimant temporairement où en les mettant en contradiction. La première perturbation a pour but de tester l'importance du référentiel locale par une rotation de 90° du labyrinthe. La permutation des bras lors d'un dernier essai permet d'induire une situation ou les informations ont été soit correctes spatialement mais incorrectes localement (texture) soit inversement. Ces perturbations des informations sensorielles qui sont fournies au sujet, permettent d'observer les systèmes de repérage et leur poids relatif dans la construction d'un système de référence durant la navigation spatiale. Les résultats du labyrinthe radial au doigt montrent que dans les conditions utilisant les informations visuelles les participants sont sensiblement plus performants. Il est apparu que les informations visuelles prédominent sur les informations proprioceptives et tactiles. Ainsi dans la condition intégrant informations visuospatiales, proprioceptives et tactiles, les sujets basent plus fortement leur navigation spatiale sur les indices visuelles soit locale soit spatiale. Dans cette condition une différence significative de stratégie entre hommes et femmes est apparue. Les hommes se basent majoritairement sur des indices spatiaux tandis que les femmes préfèrent les indices locaux. En présence d'informations tactiles et proprioceptives mais en absence de la vision, les participants utilisent les références spatiale et locale complémentairement sans avoir un système prédominant. Alors que si uniquement les informations proprioceptives sont présentes, les sujets utilisent un système de référence spatiale (globale). Le labyrinthe radial sur écran tactile indique une différence de système de référence selon l'indice local employé. Les couleurs, étant des forts indices locaux, vont favoriser un système de référence local. Au contraire les patrons noirs-blancs sont des indices visiblement très complexes et difficiles à mémoriser qui vont pousser les sujets à utiliser une stratégie de référence spatiale.

Characteristics of eyes with secondary loss of visual acuity receiving variable dosing ranibizumab for neovascular age-related macular degeneration.

PURPOSE: The aim of this work is to investigate the characteristics of eyes failing to maintain visual acuity (VA) receiving variable dosing ranibizumab for neovascular age-related macular degeneration (nAMD) after three initial loading doses. METHODS: A consecutive series of patients with nAMD, who, after three loading doses of intravitreal ranibizumab (0.5 mg each), were re-treated for fluid seen on optical coherence tomography. After exclusion of eyes with previous treatment, follow-up less than 12 months, or missed visits, 99 patients were included in the analysis. The influence of baseline characteristics, initial VA response, and central retinal thickness (CRT) fluctuations on the VA stability from month 3 to month 24 were analyzed using subgroups and multiple regression analyses. RESULTS: Mean follow-up duration was 21.3 months (range 12-40 months, 32 patients followed-up for ≥24 months). Secondary loss of VA (loss of five letters or more) after month 3 was seen in 30 patients (mean VA improvement from baseline +5.8 letters at month 3, mean loss from baseline -5.3 letters at month 12 and -9.7 at final visit up to month 24), while 69 patients maintained vision (mean gain +8.9 letters at month 3, +10.4 letters at month 12, and +12.8 letters at final visit up to month 24). Secondary loss of VA was associated with the presence of pigment epithelial detachment (PED) at baseline (p 0.01), but not with baseline fibrosis/atrophy/hemorrhage, CRT fluctuations, or initial VA response. Chart analysis revealed additional individual explanations for the secondary loss of VA, including retinal pigment epithelial tears, progressive fibrosis, and atrophy. CONCLUSIONS: Tissue damage due to degeneration of PED, retinal pigment epithelial tears, progressive fibrosis, progressive atrophy, or massive hemorrhage, appears to be relevant in causing secondary loss of VA despite vascular endothelial growth factor suppression. PED at baseline may represent a risk factor.

Selective integration of auditory-visual looming cues by humans.

An object's motion relative to an observer can confer ethologically meaningful information. Approaching or looming stimuli can signal threats/collisions to be avoided or prey to be confronted, whereas receding stimuli can signal successful escape or failed pursuit. Using movement detection and subjective ratings, we investigated the multisensory integration of looming and receding auditory and visual information by humans. While prior research has demonstrated a perceptual bias for unisensory and more recently multisensory looming stimuli, none has investigated whether there is integration of looming signals between modalities. Our findings reveal selective integration of multisensory looming stimuli. Performance was significantly enhanced for looming stimuli over all other multisensory conditions. Contrasts with static multisensory conditions indicate that only multisensory looming stimuli resulted in facilitation beyond that induced by the sheer presence of auditory-visual stimuli. Controlling for variation in physical energy replicated the advantage for multisensory looming stimuli. Finally, only looming stimuli exhibited a negative linear relationship between enhancement indices for detection speed and for subjective ratings. Maximal detection speed was attained when motion perception was already robust under unisensory conditions. The preferential integration of multisensory looming stimuli highlights that complex ethologically salient stimuli likely require synergistic cooperation between existing principles of multisensory integration. A new conceptualization of the neurophysiologic mechanisms mediating real-world multisensory perceptions and action is therefore supported.

Bilateral sequential nonarteritic anterior ischemic optic neuropathy: a comparison of visual outcomes in fellow eyes using quantitative analysis of goldmann visual fields.

OBJECTIVE To better define the concordance of visual loss in patients with nonarteritic anterior ischemic optic neuropathy (NAION). METHODS The medical records of 86 patients with bilateral sequential NAION were reviewed retrospectively, and visual function was assessed using visual acuity, Goldmann visual fields, color vision, and relative afferent papillary defect. A quantitative total visual field score and score per quadrant were analyzed for each eye using the numerical Goldmann visual field scoring method. RESULTS Outcome measures were visual acuity, visual field, color vision, and relative afferent papillary defect. A statistically significant correlation was found between fellow eyes for multiple parameters, including logMAR visual acuity (P = .01), global visual field (P < .001), superior visual field (P < .001), and inferior visual field (P < .001). The mean deviation of total (P < .001) and pattern (P < .001) deviation analyses was significantly less between fellow eyes than between first and second eyes of different patients. CONCLUSIONS Visual function between fellow eyes showed a fair to moderate correlation that was statistically significant. The pattern of vision loss was also more similar in fellow eyes than between eyes of different patients. These results may help allow better prediction of visual outcome for the second eye in patients with NAION.

Décrire et convaincre: rhétoriques visuelles de la cinématographie en médecine [Describe and convince: visual rhetoric of cinematography in medicine]

The tools of visualisation occupy a central place in medicine. Far from being simple accessories of glance, they literally constitute objects of medicine. Such empirical acknowledgement and epistemological position open a vast field of investigation: visual technologies of medical knowledge. This article studies the development and transformation of medical objects which have permitted to assess the role of temporality in the epistemology of medicine. It firstly examines the general problem of the relationships between cinema, animated image and medicine and secondly, the contribution of the German doctor Martin Weiser to medical cinematography as a method. Finally, a typology is sketched out organising the variety of the visual technology of movement under the perspective of the development of specific visual techniques in medicine.

Intraocular Straylight And Contrast Sensitivity Two Months After Lasik: Intraocular Straylight Measurement As A New Parameter In Visual Quality Assessment

PROPÒSIT: Estudiar l'efecte de la cirurgia LASIK en la llum dispersa i la sensibilitat al contrast. MÈTODES: Vint-i-vuit pacients van ser tractats amb LASIK. La qualitat visual es va avaluar abans de l'operació i dos mesos després. RESULTATS: La mitjana de llum dispersa i la sensibilitat al contrast abans de l'operació no va canviar en dos mesos després. Només un ull tenia un marcat augment en la llum dispersa. Nou ulls van presentar una lleugera disminució en la sensibilitat al contrast. S'han trobat dues complicacions. CONCLUSIÓ: Després de LASIK la majoria dels pacients (80%) no van tenir complicacions i van mantenir la seva qualitat visual. Uns pocs pacients (16%) van tenir una mica de qualitat visual disminuïda. Molt pocs (4%) van tenir complicacions clíniques amb disminució en la qualitat visual.

CoDaPack. An Excel and Visual Basic based software of compositional data analysis. Current version and discussion form upcoming versions

In the eighties, John Aitchison (1986) developed a new methodological approach for the statistical analysis of compositional data. This new methodology was implemented in Basic routines grouped under the name CODA and later NEWCODA inMatlab (Aitchison, 1997). After that, several other authors have published extensions to this methodology: Marín-Fernández and others (2000), Barceló-Vidal and others (2001), Pawlowsky-Glahn and Egozcue (2001, 2002) and Egozcue and others (2003). (...)

Net increase of lactate and glutamate concentration in activated human visual cortex detected with magnetic resonance spectroscopy at 7 tesla.

After the landmark studies reporting changes in the cerebral metabolic rate of glucose (CMRGlc ) in excess of those in oxygen (CMRO2 ) during physiological stimulation, several studies have examined the fate of the extra carbon taken up by the brain, reporting a wide range of changes in brain lactate from 20% to 250%. The present study reports functional magnetic resonance spectroscopy measurements at 7 Tesla using the enhanced sensitivity to study a small cohort (n = 6). Small increases in lactate (19% ± 4%, P < 0.05) and glutamate (4% ± 1%, P < 0.001) were seen within the first 2 min of activation. With the exception of glucose (12% ± 5%, P < 0.001), no other metabolite concentration changes beyond experimental error were significantly observed. Therefore, the present study confirms that lactate and glutamate changes during physiological stimulation are small (i.e. below 20%) and shows that the increased sensitivity allows reproduction of previous results with fewer subjects. In addition, the initial rate of glutamate and lactate concentration increases implies an increase in CMRO2 that is slightly below that of CMRGlc during the first 1-2 min of activation.

Visual management of sags and incidents gathered in distribution substations for power quality management

Monitor a distribution network implies working with a huge amount of data coining from the different elements that interact in the network. This paper presents a visualization tool that simplifies the task of searching the database for useful information applicable to fault management or preventive maintenance of the network

Visual loss after orthopedic procedures.

Perioperative visual loss (PVL) is a very rare and unpredictable complication of surgery performed at distance from the visual pathways, mostly after spine or cardiac procedures. We report 6 consecutive patients with PVL after routine orthopedic procedures (osteosynthesis for complex fracture of the femur [2], total hip arthroplasty [2], hip prosthesis arthroplasty [1], bilateral simultaneous total knee arthroplasty [1]) and reviewed the literature on the subject. An ischemic optic neuropathy was diagnosed in all cases, and visual loss was bilateral in 5 of 6 patients. Partial visual improvement occurred in only 3 of 11 eyes. No specific therapy is available for PVL. Postoperative visual disturbances should prompt without delay an ophthalmic evaluation because emergent correction of anemia, systemic hypotension, or hypovolemia might improve visual prognosis of PVL.

Positioning an underwater vehicle through image mosaicking

Mosaics have been commonly used as visual maps for undersea exploration and navigation. The position and orientation of an underwater vehicle can be calculated by integrating the apparent motion of the images which form the mosaic. A feature-based mosaicking method is proposed in this paper. The creation of the mosaic is accomplished in four stages: feature selection and matching, detection of points describing the dominant motion, homography computation and mosaic construction. In this work we demonstrate that the use of color and textures as discriminative properties of the image can improve, to a large extent, the accuracy of the constructed mosaic. The system is able to provide 3D metric information concerning the vehicle motion using the knowledge of the intrinsic parameters of the camera while integrating the measurements of an ultrasonic sensor. The experimental results of real images have been tested on the GARBI underwater vehicle

Analysis of significant factors influencing visual acuity in ocular syphilis.

BACKGROUND: The aim of this study is to determine whether statistical associations can be demonstrated in ocular syphilis between baseline clinical and laboratory parameters with visual acuity at presentation and with any change in visual acuity after treatment. METHODS: Charts of 26 patients (42 eyes) with ocular syphilis presenting to the Uveitis clinic of the Jules-Gonin Eye Hospital were reviewed. A baseline cross-sectional analysis was performed in order to identify any association between visual acuity at presentation and demographic, clinical or laboratory parameters. After treatment, any analogy between these parameters and a change in visual acuity was subsequently assessed in a series of univariate comparisons. RESULTS: The following factors were associated with worse initial visual acuity: severity of visual field impairment at presentation (p=0.012), macular oedema (p=0.004) and optic neuropathy (p=0.031). There was a borderline association with the presence of vasculitis on fluroangiography (p=0.072). Improvement in best corrected visual acuity after treatment was significantly associated with the presence of vasculitis on fluroangiography (p=0.005), neurosyphilis, according to lumbar puncture findings (p=0.037) and marginally with anterior uveitis (p=0.070). Inflammation relapse was associated with the coexistence of pain as presenting sign (p<0.001) and with a longer duration of symptoms prior to the initial visit (p=0.023). CONCLUSIONS: Severe ocular inflammation associated with vasculitis, vitritis or anterior uveitis in ocular syphilis would appear to be a reversible phenomenon that responds well to appropriate antibiotic treatment, resulting in improvement in visual acuity. Prompt treatment enables a good visual prognosis, while any delay in therapy increases the risk of subsequent relapse.

Time processing in visual cortices: How the visual brain encodes and keeps track of time

Time is embedded in any sensory experience: the movements of a dance, the rhythm of a piece of music, the words of a speaker are all examples of temporally structured sensory events. In humans, if and how visual cortices perform temporal processing remains unclear. Here we show that both primary visual cortex (V1) and extrastriate area V5/MT are causally involved in encoding and keeping time in memory and that this involvement is independent from low-level visual processing. Most importantly we demonstrate that V1 and V5/MT are functionally linked and temporally synchronized during time encoding whereas they are functionally independent and operate serially (V1 followed by V5/MT) while maintaining temporal information in working memory. These data challenge the traditional view of V1 and V5/MT as visuo-spatial features detectors and highlight the functional contribution and the temporal dynamics of these brain regions in the processing of time in millisecond range. The present project resulted in the paper entitled: 'How the visual brain encodes and keeps track of time' by Paolo Salvioni, Lysiann Kalmbach, Micah Murray and Domenica Bueti that is now submitted for publication to the Journal of Neuroscience.