Louvain-la-Neuve, Belgium
Louvain-la-Neuve, Belgium

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Alves C.H.,Meibergdreef | Sanz sanz A.,Meibergdreef | Park B.,Meibergdreef | Pellissier L.P.,Meibergdreef | And 14 more authors.
Human Molecular Genetics | Year: 2013

In humans, the Crumbs homolog-1 (CRB1) gene is mutated in progressive types of autosomal recessive retinitis pigmentosa and Leber congenital amaurosis. However, there is no clear genotype-phenotype correlation for CRB1 mutations, which suggests that other components of the CRB complex may influence the severity of retinal disease. Therefore, to understand the physiological role of the Crumbs complex proteins, we generated and analysed conditional knockout mice lacking CRB2 in the developing retina. Progressive disorganization was detected during late retinal development. Progressive thinning of the photoreceptor layer and sites of cellular mislocalization was detected throughout the CRB2-deficient retina by confocal scanning laser ophthalmoscopy and spectral domain optical coherence tomography. Under scotopic conditions using electroretinography, the attenuation of the a-wave was relatively stronger than that of the b-wave, suggesting progressive degeneration of photoreceptors in adult animals. Histological analysis of newborn mice showed abnormal lamination of immature rod photoreceptors and disruption of adherens junctions between photoreceptors, Müller glia and progenitor cells. The number of late-born progenitor cells, rod photoreceptors and Müller glia cells was increased, concomitant with programmed cell death of rod photoreceptors. The data suggest an essential role for CRB2 in proper lamination of the photoreceptor layer and suppression of proliferation of late-born retinal progenitor cells. © The Author 2012. Published by Oxford University Press. All rights reserved.

Saiepour M.H.,Institute of Visual Arts | Rajendran R.,Institute of Visual Arts | Omrani A.,Institute of Visual Arts | Ma W.-P.,University of Southern California | And 4 more authors.
Current Biology | Year: 2015

Background To ensure that neuronal networks function in a stable fashion, neurons receive balanced inhibitory and excitatory inputs. In various brain regions, this balance has been found to change temporarily during plasticity. Whether changes in inhibition have an instructive or permissive role in plasticity remains unclear. Several studies have addressed this question using ocular dominance plasticity in the visual cortex as a model, but so far, it remains controversial whether changes in inhibition drive this form of plasticity by directly affecting eye-specific responses or through increasing the plasticity potential of excitatory connections. Results We tested how three major classes of interneurons affect eye-specific responses in normally reared or monocularly deprived mice by optogenetically suppressing their activity. We find that in contrast to somatostatin-expressing or vasoactive intestinal polypeptide-expressing interneurons, parvalbumin (PV)-expressing interneurons strongly inhibit visual responses. In individual neurons of normal mice, inhibition and excitation driven by either eye are balanced, and suppressing PV interneurons does not alter ocular preference. Monocular deprivation disrupts the binocular balance of inhibition and excitation in individual neurons, causing suppression of PV interneurons to change their ocular preference. Importantly, however, these changes do not consistently favor responses to one of the eyes at the population level. Conclusions Monocular deprivation disrupts the binocular balance of inhibition and excitation of individual cells. This disbalance does not affect the overall expression of ocular dominance. Our data therefore support a permissive rather than an instructive role of inhibition in ocular dominance plasticity. © 2015 Elsevier Ltd All rights reserved.

Levelt C.N.,Institute of Visual Arts | Heimel J.A.,Institute of Visual Arts | Van Versendaal D.,Institute of Visual Arts
Neural Plasticity | Year: 2011

During the last decade, we have gained much insight into the mechanisms that open and close a sensitive period of plasticity in the visual cortex. This brings the hope that novel treatments can be developed for brain injuries requiring renewed plasticity potential and neurodevelopmental brain disorders caused by defective synaptic plasticity. One of the central mechanisms responsible for opening the sensitive period is the maturation of inhibitory innervation. Many molecular and cellular events have been identified that drive this developmental process, including signaling through BDNF and IGF-1, transcriptional control by OTX2, maturation of the extracellular matrix, and GABA-regulated inhibitory synapse formation. The mechanisms through which the development of inhibitory innervation triggers and potentially closes the sensitive period may involve plasticity of inhibitory inputs or permissive regulation of excitatory synapse plasticity. Here, we discuss the current state of knowledge in the field and open questions to be addressed. © 2011 J. Alexander Heimel et al.

van Versendaal D.,Institute of Visual Arts | Levelt C.N.,Institute of Visual Arts | Levelt C.N.,VU University Amsterdam
Cellular and Molecular Life Sciences | Year: 2016

For proper maturation of the neocortex and acquisition of specific functions and skills, exposure to sensory stimuli is vital during critical periods of development when synaptic connectivity is highly malleable. To preserve reliable cortical processing, it is essential that these critical periods end after which learning becomes more conditional and active interaction with the environment becomes more important. How these age-dependent forms of plasticity are regulated has been studied extensively in the primary visual cortex. This has revealed that inhibitory innervation plays a crucial role and that a temporary decrease in inhibition is essential for plasticity to take place. Here, we discuss how different interneuron subsets regulate plasticity during different stages of cortical maturation. We propose a theory in which different interneuron subsets select the sources of neuronal input that undergo plasticity. © 2016 The Author(s)

Sani S.M.,Institute of Visual Arts | Shokooh Y.K.,Institute of Visual Arts
2016 2nd International Conference on Web Research, ICWR 2016 | Year: 2016

With completion of web worldwide network, its users and applications have been increased too. Nowadays, one of these applications is advertising, purchase and sale of business products that has changed the websites into a complementary media and an extensive and universal context for branding and doing commercial deals. During the recent decade, minimalism has found great applications in designing user interface of business websites among web designers. They understood that minimalism with removing unnecessary aspects and Gestalt together with organizing visual elements lead to the reduction of audiences' confusion and a more extensive range of them can make a more effective interaction to website. The research methodology of this study is descriptive-Analytic and the method of gathering information library and field. This research has been investigated the minimalist design model in three top active websites in technology including Apple, Microsoft and IBM based on the Gestalt principles. This study indicates a meaningful relation between Gestalt rules and simplification of relations among visual elements in the event of achieving minimalist properties in designing these websites. The mentioned properties are: the key principle of less use, more effect through organized Gestalt perception, simplicity based on the law of similarity and proximity, removing additive elements through permanence law, making balance by using completion law and making a negative environment by informed use of Gestalt rule of shape relation. © 2016 IEEE.

Dahlhaus M.,Institute of Visual Arts | Levelt C.N.,Institute of Visual Arts
Reviews in the Neurosciences | Year: 2010

Our ability to learn relies on the potential of the neocortex to change its neuronal circuits through experience. This change is mediated by the loss or formation of synaptic contacts or the adjustment of their synaptic strength. In recent decades, the primary visual cortex has proven an excellent system for studying structure/function relationships during plasticity in the neocortex. Here we describe current knowledge about the structural changes in inhibitory or excitatory synapses that accompany experience dependent plasticity in the visual cortex. We discuss unresolved issues and technical developments that will help to provide answers in the near future. © Freund & Pettman.

Ribeiro C.,Institute of Visual Arts
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2015

his paper aim in waving reflections around the sovereignty of interaction in communicational processes focusing on Human-Computer Interaction subtleties related to informational processes in a quantum level to present and discuss the author series ‘Performing Quantum Entanglement: Subtle Apparatuses for Nonlocal Affectiveness’. The approach involves conceptualizing what the author defines as Complex Affective Systems (CAFFS), referring to multidimensional systems of interactions that lead to manifestations and incorporations of the self and the emergence of consciousness. The works selected to conduct the present conversation have been produced for the author’s solo show at the Art|Sci Gallery, CNSI/UCLA, in Los Angeles (2014), and recently for the inaugural solo show she designed for the Roy Ascott Studio Gallery in Shanghai (2015). © Springer International Publishing Switzerland 2015.

Sommeijer J.-P.,Institute of Visual Arts | Levelt C.N.,Institute of Visual Arts
PLoS ONE | Year: 2012

Background: Inhibitory innervation by parvalbumin (PV) expressing interneurons has been implicated in the onset of the sensitive period of visual plasticity. Immunohistochemical analysis of the development and plasticity of these inhibitory inputs is difficult because PV expression is low in young animals and strongly influenced by neuronal activity. Moreover, the synaptic boutons that PV neurons form onto each other cannot be distinguished from the innervated cell bodies by immunostaining for this protein because it is present throughout the cells. These problems call for the availability of a synaptic, activity-independent marker for PV+ inhibitory boutons that is expressed before sensitive period onset. We investigated whether synaptotagmin-2 (Syt2) fulfills these properties in the visual cortex. Syt2 is a synaptic vesicle protein involved in fast Ca 2+ dependent neurotransmitter release. Its mRNA expression follows a pattern similar to that of PV throughout the brain and is present in 30-40% of hippocampal PV expressing basket cells. Up to now, no quantitative analyses of Syt2 expression in the visual cortex have been carried out. Methodology/Principal Findings: We used immunohistochemistry to analyze colocalization of Syt2 with multiple interneuron markers including vesicular GABA transporter VGAT, calbindin, calretinin, somatostatin and PV in the primary visual cortex of mice during development and after dark-rearing. Conclusions/Significance: We show that in the adult visual cortex Syt2 is only found in inhibitory, VGAT positive boutons. Practically all Syt2 positive boutons also contain PV and vice versa. During development, Syt2 expression can be detected in synaptic boutons prior to PV and in contrast to PV expression, Syt2 is not down-regulated by dark-rearing. These properties of Syt2 make it an excellent marker for analyzing the development and plasticity of perisomatic inhibitory innervations onto both excitatory and inhibitory neurons in the visual cortex. © 2012 Sommeijer, Levelt.

Dahlhaus M.,Institute of Visual Arts | Li K.W.,VU University Amsterdam | Van Der Schors R.C.,VU University Amsterdam | Saiepour M.H.,Institute of Visual Arts | And 6 more authors.
Molecular and Cellular Proteomics | Year: 2011

During brain development, the neocortex shows periods of enhanced plasticity, which enables the acquisition of knowledge and skills that we use and build on in adult life. Key to persistent modifications of neuronal connectivity and plasticity of the neocortex are molecular changes occurring at the synapse. Here we used isobaric tag for relative and absolute quantification to measure levels of 467 synaptic proteins in a well-established model of plasticity in the mouse visual cortex and the regulation of its critical period. We found that inducing visual cortex plasticity by monocular deprivation during the critical period increased levels of kinases and proteins regulating the actin-cytoskeleton and endocytosis. Upon closure of the critical period with age, proteins associated with transmitter vesicle release and the tubulin- and septin-cytoskeletons increased, whereas actin-regulators decreased in line with augmented synapse stability and efficacy. Maintaining the visual cortex in a plastic state by dark rearing mice into adulthood only partially prevented these changes and increased levels of G-proteins and protein kinase A subunits. This suggests that in contrast to the general belief, dark rearing does not simply delay cortical development but may activate signaling pathways that specifically maintain or increase the plasticity potential of the visual cortex. Altogether, this study identified many novel candidate plasticity proteins and signaling pathways that mediate synaptic plasticity during critical developmental periods or restrict it in adulthood. © 2011 by The American Society for Biochemistry and Molecular Biology, Inc.

Agency: GTR | Branch: AHRC | Program: | Phase: Research Grant | Award Amount: 32.50K | Year: 2013

The Tagore, pedagogy and contemporary visual cultures network aims to bring together a group of leading international academics and visual arts practitioners to discuss and explore the legacy and continuing relevance of Indian poet and polymath Rabindranath Tagore (1861-1941) for contemporary art practice and visual culture. The group made up of artists, academics (both senior and early career researchers), curators and a political scientist, from Europe and India, have come together because they share an interest in exploring Tagores legacy and influence from different disciplinary backgrounds, often taking idiosyncratic, unorthodox approaches in order to think outside of the established conventions of Tagore scholarship. This network not only offers new opportunities for cross-disciplinary research, but proposes an original and as yet uncharted approach to Tagores work and its continuing relevance. We will meet twice in London, once in the Netherlands, and once in Santinikatan, the community school set up by Tagore in India in 1901.

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