Time filter

Source Type

Van Aerde K.I.,Jülich Research Center | Van Aerde K.I.,Royal Netherlands Academy of Arts and Science | Feldmeyer D.,Jülich Research Center | Feldmeyer D.,RWTH Aachen | Feldmeyer D.,Julich Aachen Research Alliance
Cerebral Cortex | Year: 2015

The medial prefrontal cortex (mPFC) has been implicated in cognitive and executive processes including decision making, working memory and behavioral flexibility. Cortical processing depends on the interaction between distinct neuronal cell types in different cortical layers. To better understand cortical processing in the rat mPFC, we studied the diversity of pyramidal neurons using in vitro whole-cell patch clamp recordings and biocytin staining of neurons, followed by morphological analysis. Using unsupervised cluster analysis for the objective grouping of neurons, we identified more than 10 different pyramidal subtypes spread across the different cortical layers. Layer 2 pyramidal neurons possessed a unique morphology with wide apical dendritic field spans and a narrow basal field span. Layer 3 contained the only subtype that showed a burst of action potentials upon current injection. Layer 5 pyramidal neurons showed the largest voltage sags. Finally, pyramidal neurons in layer 6 (L6) showed a great variety in their morphology with 39% of L6 neurons possessing tall apical dendrites that extend into layer 1. Future experiments on the functional role of the mPFC should take into account the great diversity of pyramidal neurons. © 2013 The Author.

Clevers H.,Royal Netherlands Academy of Arts and science | Clevers H.,University Utrecht
Cell | Year: 2013

Due to its intense self-renewal kinetics and its simple repetitive architecture, the intestinal epithelium has become a prime model for studying adult stem cells in health and disease. Transgenic mouse models allow in vivo visualization and genetic lineage tracing of individual intestinal stem cells and their offspring. Fluorescently marked stem cells can be isolated for molecular analyses or can be cultured to build ever-expanding "mini-guts" in vitro. These studies are filling in the outlines of a robust homeostatic self-renewal process that defies some of the classical definitions of stem cell behavior, such as asymmetric division, quiescence, and exhaustion. © 2013 Elsevier Inc.

Grun D.,Royal Netherlands Academy of Arts and science | Grun D.,University Utrecht | Kester L.,Royal Netherlands Academy of Arts and science | Kester L.,University Utrecht | And 2 more authors.
Nature Methods | Year: 2014

Single-cell transcriptomics has recently emerged as a powerful technology to explore gene expression heterogeneity among single cells. Here we identify two major sources of technical variability: sampling noise and global cell-to-cell variation in sequencing efficiency. We propose noise models to correct for this, which we validate using single-molecule FISH. We demonstrate that gene expression variability in mouse embryonic stem cells depends on the culture condition. © 2014 Nature America, Inc.

Ausloos M.,Royal Netherlands Academy of Arts and science
Central European Journal of Physics | Year: 2014

A strong structural regularity of classes is found in soccer teams ranked by the Union of European Football Associations (UEFA) for the time interval 2009-2014. It concerns 424 to 453 teams according to the 5 competition seasons. The analysis is based on the rank-size theory considerations, the size being the UEFA coefficient at the end of a season. Three classes emerge: (i) the few "top" teams, (ii) 300 teams, (iii) the rest of the involved teams (about 150) in the tail of the distribution. There are marked empirical laws describing each class. A 3-parameter Lavalette function is used to describe the concave curving as the rank increases, and to distinguish the the tail from the central behavior. © 2014 Versita Warsaw and Springer-Verlag Wien.

Hofman M.A.,Royal Netherlands Academy of Arts and science
Frontiers in Neuroanatomy | Year: 2014

Comparative studies of the brain in mammals suggest that there are general architectural principles governing its growth and evolutionary development. We are beginning to understand the geometric, biophysical and energy constraints that have governed the evolution and functional organization of the brain and its underlying neuronal network. The object of this review is to present current perspectives on primate brain evolution, especially in humans, and to examine some hypothetical organizing principles that underlie the brain's complex organization. Some of the design principles and operational modes that underlie the information processing capacity of the cerebral cortex in primates will be explored. It is shown that the development of the cortex coordinates folding with connectivity in a way that produces smaller and faster brains, then otherwise would have been possible. In view of the central importance placed on brain evolution in explaining the success of our own species, one may wonder whether there are physical limits that constrain its processing power and evolutionary potential. It will be argued that at a brain size of about 3500 cm3, corresponding to a brain volume two to three times that of modern man, the brain seems to reach its maximum processing capacity. The larger the brain grows beyond this critical size, the less efficient it will become, thus limiting any improvement in cognitive power. © 2014 Hofman.

The human cerebral cortex contains numerous myelinated fibres, many of which are concentrated in tangentially organized layers and radially oriented bundles. The spatial organization of these fibres is by no means homogeneous throughout the cortex. Local differences in the thickness and compactness of the fibre layers, and in the length and strength of the radial bundles renders it possible to recognize areas with a different myeloarchitecture. The neuroanatomical subdiscipline aimed at the identification and delineation of such areas is known as myeloarchitectonics. There is another, closely related neuroanatomical subdiscipline, named cytoarchitectonics. The aims and scope of this subdiscipline are the same as those of myeloarchitectonics, viz. parcellation. However, this subdiscipline focuses, as its name implies, on the size, shape and arrangement of the neuronal cell bodies in the cortex, rather than on the myelinated fibres. At the beginning of the twentieth century, two young investigators, Oskar and Cécile Vogt founded a centre for brain research, aimed to be devoted to the study of the (cyto + myelo) architecture of the cerebral cortex. The study of the cytoarchitecture was entrusted to their collaborator Korbinian Brodmann, who gained great fame with the creation of a cytoarchitectonic map of the human cerebral cortex. Here, we focus on the myeloarchitectonic studies on the cerebral cortex of the Vogt-Vogt school, because these studies are nearly forgotten in the present attempts to localize functional activations and to interprete findings in modern neuroimaging studies. Following introductory sections on the principles of myeloarchitectonics, and on the achievements of three myeloarchitectonic pioneers who did not belong to the Vogt-Vogt school, the pertinent literature is reviewed in some detail. These studies allow the conclusion that the human neocortex contains about 185 myeloarchitectonic areas, 70 frontal, 6 insular, 30 parietal, 19 occipital, and 60 temporal. It is emphasized that the data available, render it possible to compose a myeloarchitectonic map of the human neocortex, which is at least as reliable as any of the classic architectonic maps. During the realization of their myeloarchitectonic research program, in which numerous able collaborators were involved, the Vogts gradually developed a general concept of the organization of the cerebral cortex. The essence of this concept is that this structure is composed of about 200 distinct, juxtaposed 'Rindenfelder' or 'topistische Einheiten', which represent fundamental structural as well as functional entities. The second main part of this article is devoted to a discussion and evaluation of this 'Vogt-Vogt concept'. It is concluded that there is converging quantitative cytoarchitectonic, receptor architectonic, myeloarchitectonic, hodological, and functional evidence, indicating that this concept is essentially correct. The third, and final part of this article deals with the problem of relating particular cortical functions, as determined with neuroimaging techniques, to particular cortical structures. At present, these 'translation' operations are generally based on adapted, three-dimensional versions of Brodmann's famous map. However, it has become increasingly clear that these maps do not provide the neuroanatomical precision to match the considerable degree of functional segregation, suggested by neuroimaging studies. Therefore, we strongly recommend an attempt at combining and synthesizing the results of Brodmann's cytoarchitectonic analysis, with those of the detailed myeloarchitectonic studies of the Vogt-Vogt school. These studies may also be of interest for the interpretation of the myeloarchitectonic features, visualized in modern in vivo mappings of the human cortex. © 2012 Springer-Verlag Berlin Heidelberg.

Roelfsema P.R.,Royal Netherlands Academy of Arts and science | Roelfsema P.R.,VU University Amsterdam
Science | Year: 2011

Monkeys are able to increase and decrease the activity of single neurons involved in vision.

Ausloos M.,Royal Netherlands Academy of Arts and science
Scientometrics | Year: 2014

Each co-author (CA) of any scientist can be given a rank (r) of importance according to the number (J) of joint publications which the authors have together. In this paper, the Zipf–Mandelbrot–Pareto law, i.e. (formula presented) is shown to reproduce the empirical relationship between J and r and shown to be preferable to a mere power law, (formula presented). The CA core value, i.e. the core number of CAs, is unaffected, of course. The demonstration is made on data for two authors, with a high number of joint publications, recently considered by Bougrine (Scientometrics, 98(2): 1047–1064, 2014) and for seven authors, distinguishing between their “journal” and “proceedings” publications as suggested by Miskiewicz (Physica A, 392(20), 5119–5131, 2013). The rank-size statistics is discussed and the α and ζ exponents are compared. The correlation coefficient is much improved (~0.99, instead of 0.92). There are marked deviations of such a co-authorship popularity law depending on sub-fields. On one hand, this suggests an interpretation of the parameter v. On the other hand, it suggests a novel model on the (likely time dependent) structural and publishing properties of research teams. Thus, one can propose a scenario for how a research team is formed and grows. This is based on a hierarchy utility concept, justifying the empirical Zipf–Mandelbrot–Pareto law, assuming a simple form for the CA publication/cost ratio, (formula presented) . In conclusion, such a law and model can suggest practical applications on measures of research teams. In Appendices, the frequency-size cumulative distribution function is discussed for two sub-fields, with other technicalities. © 2014, Akadémiai Kiadó, Budapest, Hungary.

Dalen-Oskam K.V.,Royal Netherlands Academy of Arts and science
Literary and Linguistic Computing | Year: 2013

Proper names in literary texts have different functions. The most important one in real life, identification, is only one of these. Some others are to make the fiction more 'real' or to present ideas about a character by using a name with certain meanings or associations to manipulate the reader's expectations. A description of the functions of a certain name in a certain text becomes relevant when the researcher can point out how it compares to the functions of other names and names in other texts. The article describes how research into names in literary texts needs a quantitative approach to reach a higher level of relevancy. To get a first impression of what may be normal in literary texts, a corpus of twenty-two Dutch and twenty-two English novels and ten translations into the other language in both sets were gathered. The occurrences of all names in these novels have been tagged for those data categories that seemed useful for the literary stylistic research planned. Some first results of the statistics are presented and the use of the approach is illustrated by means of an analysis of the use of geographical names in the Dutch novel Boven is het stil by Gerbrand Bakker and its English translation by David Colmer, The Twin. In the evaluation of the results, special attention is paid to the status of currently available digital tools for named entity recognition and classification, followed by a wish-list for the tools that this kind of research really needs. © The Author 2012. Published by Oxford University Press on behalf of ALLC. All rights reserved.

Van Bree M.C.J.,Rotterdam Ophthalmic Institute | Van Den Berg T.J.T.P.,Royal Netherlands Academy of Arts and science | Zijlmans B.L.M.,Rotterdam Eye Hospital
Ophthalmology | Year: 2013

Purpose: To study the effect of posterior capsule opacification (PCO) morphology and severity on different aspects of visual function (VF): the small-angle domain (visual acuity [VA], contrast sensitivity [CS]) and large-angle domain (straylight; logarithm of the straylight parameter s [log{s}]). To evaluate whether straylight is a valuable additional indicator for appropriate posterior capsulotomy referral. Design: Prospective, comparative study. Participants and Controls: For the study population, 240 pseudophakic eyes with PCO and a capsulotomy indication were selected. For the reference population, 99 pseudophakic eyes without PCO were selected. Methods: The relation between PCO morphology and PCO severity and the precapsulotomy and postcapsulotomy logarithm of the minimum angle of resolution (logMAR), logarithm of CS (log[CS]), and log(s) values were determined. The PCO severity was assessed with retroillumination using evaluation of posterior capsule opacification (EPCO) software. Precapsulotomy logMAR and log(s) values were used to predict functionally significant logMAR and log(s) improvement after capsulotomy. Main Outcome Measures: The logMAR, log(CS), and log(s) improvements of ≥0.20 log units were considered functionally significant (i.e., treatment effect). Precapsulotomy logMAR and log(s) values, above which a treatment effect (improvement ≥0.20 log units) can be expected with ≥50% probability, were determined and called cutoff values. Results: Postcapsulotomy VF improvement was related to precapsulotomy VF values: Postcapsulotomy improvement was largest in cases with substantially impaired precapsulotomy VF parameters. Visual function deterioration was related to PCO severity rather than PCO morphology. The PCO severity (EPCO score) assessed with retroillumination has a progressive, linear relation with log(s) and a curvilinear relation with logMAR. Reflected light examination is expected to overestimate functional PCO severity. The precapsulotomy cutoff value was ≥1.44 for log(s) and ≥0.21 for logMAR. Conclusions: The linear relation between retroillumination PCO severity and log(s) indicates that log(s) is sensitive to low PCO severity, whereas the curvilinear relation between PCO severity and logMAR indicates that logMAR is unaffected by low PCO severity. Straylight is a sensitive, additional indicator for capsulotomy referral, especially in less severe cases of PCO. In ophthalmic practice, the precapsulotomy log(s) cutoff value of 1.44 can be used as an indicator for beneficial capsulotomy referral. Financial Disclosure(s): The author(s) have no proprietary or commercial interest in any materials discussed in this article. © 2013 American Academy of Ophthalmology.

Loading Royal Netherlands Academy of Arts and science collaborators
Loading Royal Netherlands Academy of Arts and science collaborators