1,721,008 research outputs found
Development of a framework to link functional activity and circuit wiring diagrams in the zebrafish larva brain
Full text linkIn recent years, there has been a significant increase in the developing of techniques to study the brain, both in terms of the function and of the connectivity organization. Whole brain dense anatomical reconstruction at synaptic resolution have provided insight into the brain architecture and how the information is transmitted. However, these reconstructions, even when the synaptic input/output relationship are known, are still far from revealing the general connectivity patterns of the neuronal circuits across the brain and their functional organization in networks. On the other hand, light based techniques allow the functional characterization of the neuronal activity associated with resting state activity or sensory-driven dynamics. Here, we present two methods to analyze the circuit mechanisms on the zebrafish larvae, a small vertebrate with a completely optical accessible brain. First, a tool for identifying functionally relevant networks based on their structural connectivity patterns which is adaptable to different anatomical datasets with or without identified synapses. Second, an alternative optical layout for high resolution whole-brain imaging which can be used to reconstruct the brain dynamics during sensory stimulation. The combination of these two tools can provide a deeper understanding on how the structure of the nervous system supports the flow of information and offer a more accurate basis for the formulation of models of the circuit working principles.In recent years, there has been a significant increase in the developing of techniques to study the brain, both in terms of the function and of the connectivity organization. Whole brain dense anatomical reconstruction at synaptic resolution have provided insight into the brain architecture and how the information is transmitted. However, these reconstructions, even when the synaptic input/output relationship are known, are still far from revealing the general connectivity patterns of the neuronal circuits across the brain and their functional organization in networks. On the other hand, light based techniques allow the functional characterization of the neuronal activity associated with resting state activity or sensory-driven dynamics. Here, we present two methods to analyze the circuit mechanisms on the zebrafish larvae, a small vertebrate with a completely optical accessible brain. First, a tool for identifying functionally relevant networks based on their structural connectivity patterns which is adaptable to different anatomical datasets with or without identified synapses. Second, an alternative optical layout for high resolution whole-brain imaging which can be used to reconstruct the brain dynamics during sensory stimulation. The combination of these two tools can provide a deeper understanding on how the structure of the nervous system supports the flow of information and offer a more accurate basis for the formulation of models of the circuit working principles
Innate visual discrimination abilities of zebrafish larvae
No full textThe ability to discriminate between objects visually plays a key role in animals’ interactions with their environment because it enables them to recognise companions, prey, and predators. In the zebrafish, Danio rerio, hatching occurs early on during development (48–72 h post fertilisation), and the larvae must forage and evade predators despite their immature sensory and cognitive systems. Using a preference paradigm, we investigated whether larval zebrafish are nonetheless capable of discriminating between visual stimuli. We found that larvae discriminated not only between figures with different colours or different shapes, but also between two identical figures with different orientations and between sets of figures with different numerosities. By manipulating larvae’s exposure to objects before the test, we demonstrated that their discrimination abilities are innate and do not depend upon experience. This study highlighted that zebrafish possess relatively sophisticated visual discrimination abilities even at the larval stage. These abilities likely improve larval survival via the recognition of biologically relevant stimuli
A Single Sub-Millimetric Metasurface-Based Optical Element for Lattice Bessel Beam Excitation Enabling Brain Activity Recordings In Vivo
Full text linkBessel beams (BBs) are propagation-invariant optical fields that retain a narrow central intensity profile over longer propagation lengths than Gaussian beams (GBs). Due to this property, they have been adopted in fluorescence-based light sheet microscopy (LSM) to obtain 2D longitudinally-extended light-sheets. Yet, current approaches for generating BB lattices in LSM focus on regular excitation patterns and involve complex and bulky optics, limiting integration capability and versatility. Here, a flexible method is presented to obtain BB-arrays with arbitrary geometries by encoding on a single sub-millimetric surface all the optical transformations required. This method is applied using a single metasurface to encode the generation of a linear array of BBs, avoiding the use of conjugation and focusing optics. With respect to the current strategies, this approach, allowing for the independent design of each beamlet of the array, increases the degrees of freedom while making optimal use of the available light with no rejection, thus facilitating its integration into optical systems. According to this method, we fabricated a metasurface-based optical element for generating a linear BB-array of excitation in an LSM configuration and recorded neuronal activity at cellular resolution from the zebrafish larva brain. Thus, the proposed approach greatly extends the BB-array versatility and the application scenarios.LNE
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Optogenetic Methods to Investigate Brain Alterations in Preclinical Models
Full text linkInvestigating the neuronal dynamics supporting brain functions and understanding how the alterations in these mechanisms result in pathological conditions represents a fundamental challenge. Preclinical research on model organisms allows for a multiscale and multiparametric analysis in vivo of the neuronal mechanisms and holds the potential for better linking the symptoms of a neurological disorder to the underlying cellular and circuit alterations, eventually leading to the identification of therapeutic/rescue strategies. In recent years, brain research in model organisms has taken advantage, along with other techniques, of the development and continuous refinement of methods that use light and optical approaches to reconstruct the activity of brain circuits at the cellular and system levels, and to probe the impact of the different neuronal components in the observed dynamics. These tools, combining low-invasiveness of optical approaches with the power of genetic engineering, are currently revolutionizing the way, the scale and the perspective of investigating brain diseases. The aim of this review is to describe how brain functions can be investigated with optical approaches currently available and to illustrate how these techniques have been adopted to study pathological alterations of brain physiology
Light-Based Neuronal Circuit Probing in Living Brains at High Resolution: Constraints and Layouts for Integrating Neuronal Activity Recording and Modulation in Three Dimensions
Full text linkDispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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