1,720,958 research outputs found
The anterior paired lateral neuron normalizes odour-evoked activity at the mushroom body calyx
No full textThe anterior paired lateral neuron normalizes odour-evoked activity in the Drosophila mushroom body calyx
No full textTo identify and memorize discrete but similar environmental inputs, the brain needs to distinguish between subtle differences of activity patterns in defined neuronal populations. The Kenyon cells (KCs) of the Drosophila adult mushroom body (MB) respond sparsely to complex olfactory input, a property that is thought to support stimuli discrimination in the MB. To understand how this property emerges, we investigated the role of the inhibitory anterior paired lateral (APL) neuron in the input circuit of the MB, the calyx. Within the calyx, presynaptic boutons of projection neurons (PNs) form large synaptic microglomeruli (MGs) with dendrites of postsynaptic KCs. Combining electron microscopy (EM) data analysis and in vivo calcium imaging, we show that APL, via inhibitory and reciprocal synapses targeting both PN boutons and KC dendrites, normalizes odour-evoked representations in MGs of the calyx. APL response scales with the PN input strength and is regionalized around PN input distribution. Our data indicate that the formation of a sparse code by the KCs requires APL-driven normalization of their MG postsynaptic responses. This work provides experimental insights on how inhibition shapes sensory information representation in a higher brain centre, thereby supporting stimuli discrimination and allowing for efficient associative memory formation
The caloric value of food intake structurally adjusts a neuronal mushroom body circuit mediating olfactory learning in Drosophila
No full textAssociative learning enables the adaptive adjustment of behavioral decisions based on acquired, predicted outcomes. The valence of what is learned is influenced not only by the learned stimuli and their temporal relations, but also by prior experiences and internal states. In this study, we used the fruit fly Drosophila melanogaster to demonstrate that neuronal circuits involved in associative olfactory learning undergo restructuring during extended periods of low-caloric food intake. Specifically, we observed a decrease in the connections between specific dopaminergic neurons (DANs) and Kenyon cells at distinct compartments of the mushroom body. This structural synaptic plasticity was contingent upon the presence of allatostatin A receptors in specific DANs and could be mimicked optogenetically by expressing a light-activated adenylate cyclase in exactly these DANs. Importantly, we found that this rearrangement in synaptic connections influenced aversive, punishment-induced olfactory learning but did not impact appetitive, reward-based learning. Whether induced by prolonged low-caloric conditions or optogenetic manipulation of cAMP levels, this synaptic rearrangement resulted in a reduction of aversive associative learning. Consequently, the balance between positive and negative reinforcing signals shifted, diminishing the ability to learn to avoid odor cues signaling negative outcomes. These results exemplify how a neuronal circuit required for learning and memory undergoes structural plasticity dependent on prior experiences of the nutritional value of food
Functional dissection of a neuronal brain circuit mediating higher-order associative learning
No full texthttp://dx.doi.org/10.13039/501100004663 Ministry of Science and Technology, Taiwanhttp://dx.doi.org/10.13039/100011937 Lower Saxony State Ministry of Science and Culturehttp://dx.doi.org/10.13039/501100001869 Academia Sinicahttp://dx.doi.org/10.13039/501100001659 Deutsche Forschungsgemeinschafthttp://dx.doi.org/10.13039/501100010570 Niedersächsisches Ministerium für Wissenschaft und Kulturhttp://dx.doi.org/10.13039/501100002347 Federal Ministry of Education and Research Bonn OfficeOpen-Access-Publikationsfonds 202
Learning-dependent plasticity of the Drosophila mushroom body: An optophysiological approach
Full text linkFunctional changes in the neuronal network of our brain enable experience-dependent adaptations to the environment through our behavior, referred to as learning and memory. One fundamental topic has occupied the neurosciences from the very beginning: understanding the mechanism of memory formation and its localization in the brain. Synaptic plasticity emerges as a key mechanism in this process, whereby neurons within a circuit adjust their connectivity to enable memory formation. Given that a single neuron can interact with multiple synaptic partners, mechanisms must regulate synaptic plasticity to individual subcellular segments to facilitate the formation of complex circuits.
The aim of this thesis is to investigate the localization of synaptic plasticity and elucidate the underlying mechanisms for subcellular confinement. Focusing primarily on learning-dependent plasticity, the Drosophila mushroom body serves as an accessible model due to its central role in olfactory learning. Throughout this work, comprehensive and novel optophysiological approaches, such as functional in-vivo cAMP imaging with single cell resolution, were used across various research topics to investigate synaptic plasticity during learning and memory.
The thesis addresses a wide range of projects, each covering different behavioral implications within the context of learning-dependent plasticity. Central to these investigations is the role of the second messenger cAMP, which plays a crucial part in regulating plasticity and is restricted by the phosphodiesterase Dunce. The main part of this work focuses on the investigation of the intracellular confinement of cAMP signaling by Dunce as a mechanism of subcellular compartmentalization. The findings reveal that the phosphodiesterase Dunce serves as a key regulator of the compartmentalization of subcellular cAMP signals, offering valuable insights into subcellular segments as independent units in learning and memory. Based on this, future studies can be designed to investigate the relation of confined cAMP dynamics and synaptic plasticity and thus contribute to the understanding of memory formation and localization.2024-08-0
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
Dispelling 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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