How a Subclinical Unilateral Vestibular Signal Improves Binocular Vision

The present study aimed to determine if an infra-liminal asymmetric vestibular signal could account for some of the visual complaints commonly encountered in chronic vestibular patients. We used infra-liminal galvanic vestibular stimulation (GVS) to investigate its potential effects on visuo-oculomotor behavior. A total of 78 healthy volunteers, 34 aged from 20 to 25 years old and 44 aged from 40 to 60 years old, were included in a crossover study to assess the impact of infra-liminal stimulation on convergence, divergence, proximal convergence point, and stereopsis. Under GVS stimulation, a repeated measures ANOVA showed a significant variation in near convergence (p < 0.001), far convergence (p < 0.001), and far divergence (p = 0.052). We also observed an unexpected effect of instantaneous blocking of the retest effect on the far divergence measurement. Further investigations are necessary to establish causal relationships, but GVS could be considered a behavioral modulator in non-pharmacological vestibular therapies

Neural correlates of chromostereopsis: an evoked potential study.

International audienceChromostereopsis is an illusion of depth arising from colour contrast: ocular chromatic aberrations usually make red appear closer to the viewer than blue. Whereas this phenomenon is widely documented from the optical and psychophysical point of view, its neural correlates have not been investigated. To determine the cortical processing of this colour-based depth effect, visual evoked potentials (VEPs) to contrasts of colour were recorded in 25 subjects. Chromostereopsis was found with the stimuli combining spectra extremes. VEP amplitude but not latency effects were observed to colour depth cues, suggesting an underlying, depth-specific slow negative wave, located using source modelling first in occipito-parietal, parietal, then temporal areas. The component was larger over the right hemisphere consistent with RH dominance in depth processing, likely due to context-dependent top-down modulation. These results demonstrate that the depth illusion obtained from contrast of colour implicates similar cortical areas as classic binocular depth perception

V6 is active during antero-posterior but not in lateral galvanic vestibular stimulation.

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Parkinson’s patients can rely on perspective cues to perceive 3D space

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BtID -Outils pour identifier, tracer et contrôler les contaminants de Bacillus thuringiensis de la fourche à la fourchette

Bacillus thuringiensis ou Bt est une bactérie ubiquiste utilisée dans le domaine agricole en protection des cultures pour ses propriétés insecticides depuis les années 1950. Au niveau taxonomique, Bt appartient au groupe Bacillus cereus (sensu lato), qui contient également des souches pouvant être impliquées dans la qualité et sécurité des aliments. Même si l’utilisation de produits phytosanitaires à base de souches commerciales de Bt est un moyen efficace, facile d’utilisation et avantageux pour la protection des cultures, la persistance de spores sur les végétaux traités n’est pas toujours compatible avec les critères microbiologiques fixés pour leur utilisation dans les denrées alimentaires. Le projet BtID a permis (1) d’évaluer la diversité de B. thuringiensis et le positionnement de souches commerciales au sein du groupe B. cereus ; (2) de passer en revue les pratiques agricoles pour la protection des plantes à base de Bt ainsi que (3) de développer des méthodologies et outils d’aide à la décision permettant d’identifier, distinguer et tracer les souches de Bt autorisées au niveau européen, du champ à l’assiette. La collecte de ces souches commerciales a permis le séquençage du génome de trois représentants distincts majoritaires utilisés en biocontrôle, une caractérisation fine du comportement de ces souches hautement spécialisées, ainsi que d’étudier leur prévalence au niveau des matières premières (légumes) et produits finis (alimentaires transformés)

Poststroke conscious visual deficit: clinical course and changes in cerebral activations.

International audienceBACKGROUND: and PURPOSE: . Little is known about the outcome and recovery mechanisms of visual perception after a focal lesion of the occipital lobe in humans, especially after stroke. In this study, the authors aimed to describe the clinical course and the neural substrates of conscious perceptive visual deficit after posterior cerebral artery infarct. METHODS: . The authors prospectively included 8 patients (7 men and 1 woman; mean age, 64.6 ± 18 years) with visual deficit induced by partial damage of the striate cortex related to acute posterior cerebral artery infarct. Conscious perception of color and motion was assessed from the acute phase to the third month. Functional magnetic resonance imaging was performed to investigate neural substrates of visual recovery. RESULTS: . In the acute phase of stroke, visual deficiency was global (3/8 patients), selective to color (4/8 patients), or selective to motion (1/8 patients). During the follow-up, visual performance increased with respect to color (from 29% to 70%; P < .005) and with respect to motion (from 47% to 74%; P < .005). Despite a lack of ipsilesional V1 area activation in the acute phase, activations in this area and in the contralesional extrastriate cortex were obtained during follow-up. Both ipsilesional and contralesional V4 activations were correlated with better outcome. CONCLUSIONS: . Extensive visual recovery occurs early after partial acute posterior cerebral artery infarct. Spared islands in ipsilesional V1 area and transcallosal pathways might be involved in poststroke visual recovery

Antero-Posterior vs. Lateral Vestibular Input Processing in Human Visual Cortex

International audienceVisuo-vestibular integration is crucial for locomotion, yet the cortical mechanismsinvolved remain poorly understood. We combined binaural monopolar galvanic vestibularstimulation (GVS) and functional magnetic resonance imaging (fMRI) to characterize thecortical networks activated during antero-posterior and lateral stimulations in humans.We focused on functional areas that selectively respond to egomotion-consistent opticflow patterns: the human middle temporal complex (hMT+), V6, the ventral intraparietal(VIP) area, the cingulate sulcus visual (CSv) area and the posterior insular cortex (PIC).Areas hMT+, CSv, and PIC were equivalently responsive during lateral and antero-posterior GVS while areas VIP and V6 were highly activated during antero-posteriorGVS, but remained silent during lateral GVS. Using psychophysiological interaction (PPI)analyses, we confirmed that a cortical network including areas V6 and VIP is engagedduring antero-posterior GVS. Our results suggest that V6 and VIP play a specific role inprocessing multisensory signals specific to locomotion during navigatio

Brainsourcing: Crowdsourcing Recognition Tasks via Collaborative Brain-Computer Interfacing

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At what stage of neural processing do perspective depth cues make a difference?

The present study investigated the cortical processing of three-dimensional (3D) perspective cues in humans, to determine how the brain computes depth from a bidimensional retinal image. We recorded visual evoked potentials in 12 subjects in response to flat and in-perspective stimuli, which evoked biphasic potentials over posterior electrodes. The first, positive component (P1, at 90 ms) was not sensitive to perspective, while the second, negative peak (N1 at ~150 ms) was significantly larger for 3D stimuli, regardless of attention. The amplitude increase due to perspective was seen on all posterior electrodes, but was largest over the right hemisphere, particularly at parietal sites. Source modeling low-resolution electromagnetic tomography (LORETA) confirmed that among the different areas participating in two- and three-dimensional stimuli processing, the right parietal source is the most enhanced by perspective depth cues. We conclude that the extraction of depth from perspective cues occurs at a second level of stimulus processing, by increasing the activity of the regions involved in 2D stimuli processing, particularly in the right hemisphere, possibly through feedback loops from higher cortical areas. These modulations would participate in the fine-tuned analysis of the 3D features of stimuli