1,720,970 research outputs found
Whole- Brain Functional Ultrasound Imaging Reveals Brain Modules for Visuomotor Integration
No full textLarge numbers of brain regions are active during behaviors. A high-resolution, brain-wide activity map could identify brain regions involved in specific behaviors. We have developed functional ultrasound imaging to record whole-brain activity in behaving mice at a resolution of ∼100 μm. We detected 87 active brain regions during visual stimulation that evoked the optokinetic reflex, a visuomotor behavior that stabilizes the gaze both horizontally and vertically. Using a genetic mouse model of congenital nystagmus incapable of generating the horizontal reflex, we identified a subset of regions whose activity was reflex dependent. By blocking eye motion in control animals, we further separated regions whose activity depended on the reflex's motor output. Remarkably, all reflex-dependent but eye motion-independent regions were located in the thalamus. Our work identifies functional modules of brain regions involved in sensorimotor integration and provides an experimental approach to monitor whole-brain activity of mice in normal and disease states.sponsorship: We thank A. Drinnenberg, G. Kosche, D. Hillier, P. King, and S. Oakeley for commenting on the manuscript. We thank P. Argast for assistance with the head and probe holder prototyping. We acknowledge the following grants: Human Frontier Science Program Postdoctoral Fellowship (LT000769/2015) to E.M.; Swiss National Science Foundation Ambizione Grant (PZOOP3_168213) and Canada Research Chair Grant to S.T.; Swiss National Science Foundation grants (3100330B_163457), the National Center of Competence in Research Molecular Systems Engineering grant, European Research Council (669157, RETMUS), and DARPA (HR0011-17-C-0038, Cortical Sight) grants to B.R. (Human Frontier Science Program Postdoctoral Fellowship|LT000769/2015, Swiss National Science Foundation Ambizione Grant|PZOOP3_168213, Canada Research Chair Grant, Swiss National Science Foundation|3100330B_163457, European Research Council|669157, DARPA|HR0011-17-C-0038, National Center of Competence in Research Molecular Systems Engineering grant, European Research Council (ERC)|669157)status: Publishe
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
Visual objects refine head direction coding
No full textAnimals use visual objects to guide navigation-related behaviors. However, visual object–preferring areas have yet to be described in the mouse brain, limiting our understanding of how visual objects affect spatial navigation system processing. Using functional ultrasound imaging, we identified brain areas that were preferentially activated by images of objects compared with their scrambled versions. Whereas visual cortex did not show a preference, areas associated with spatial navigation were preferentially activated by visual objects. Electrophysiological recordings in postsubiculum, the cortical head direction (HD) system hub, confirmed a preference for visual objects in both HD cells and fast-spiking interneurons. In freely moving animals, visual objects increased firing rates of HD cells aligned with a visual object but decreased activity in HD cells coding for other directions.Editor’s summary Although much of the visual system is dedicated to processing objects, we still don’t fully understand how visual objects affect spatial information coding. Siegenthaler et al . used functional ultrasound imaging to screen for mouse brain areas strongly activated by visual objects. At the brain network level, the spatial navigation system, not the ventral visual stream as in primates, exhibited a robust preference for visual objects. At the brain region level, one of the top hits of the ultrasound screen was the postsubiculum, an area with many head direction cells. In recordings from postsubiculum cells in freely moving mice, visual objects boosted the firing rate of head direction cells, with preferred firing directions pointing toward the object, and decreased the firing of cells that encoded other head directions. —Peter SternINTRODUCTION In our day-to-day life, we use visual objects (e.g., a specific clock tower when walking around town, etc.) as spatial landmarks to help orientate ourselves as we make our way through the world. We can use visual objects as spatial landmarks because our brains dedicate considerable computational power toward parsing the world into objects. Moreover, our location in the world is processed by specialized cells such as place cells, grid cells, and head direction (HD) cells in the brain’s spatial navigation system. However, much remains unknown about how visual objects modulate tuning properties of the neurons that encode spatial variables, partly because it is unclear how visual objects are processed in the rodent brain, where spatial navigation signals have been most extensively studied. RATIONALE To address this gap in knowledge, we reasoned that a brainwide activity screen in mice could identify visual object–preferring areas in an unbiased way. Using electrophysiology, we then characterized the spatial correlates of individual neurons in the areas responding to objects in freely moving mice. RESULTS Our brainwide screen based on functional ultrasound imaging revealed that spatial navigation–related areas, not visual cortical areas, tended to show a preference for visual objects. The postsubiculum, a hub of the HD system, exhibited the strongest object preference. In head-fixed conditions, we discovered that HD cells were differentially modulated by visual stimulation based on their preferred firing direction: HD cells pointing toward the visual stimulus were excited, whereas HD cells pointing away from the visual stimulus were inhibited. The same modulation was observed in freely moving conditions, when an object was displayed in the environment. CONCLUSION Visual objects refine the population encoding of HD in the postsubiculum by increasing the response of HD cells that code toward the object while simultaneously decreasing the firing rate of HD cells that code directions away from the object. As an analogy, imagine yourself wandering around a city with a compass (which, in our experiments, is the brain’s HD system), and each time you look at a landmark (which, in our experiments, is an image of an object), the compass needle becomes more stable and thus more accurate. Together, these results provide insights into how the brain uses visual landmarks to dynamically enhance the encoding of spatial information about the world. Visual objects sharpen the representation of head direction. Of all visually responsive regions, the most object-preferring areas belonged to the spatial navigation system. Electrophysiological analysis in one of the identified regions, the postsubiculum, indicated that when an animal faces a visual landmark, HD encoding is refined. W, west; N, north; E, east; S, south. [Three-dimensional brain images prepared with cocoframer © 2018 Allen Institute for Brain Science. Allen Brain Explorer]Animals use visual objects to guide navigation-related behaviors. However, visual object–preferring areas have yet to be described in the mouse brain, limiting our understanding of how visual objects affect spatial navigation system processing. Using functional ultrasound imaging, we identified brain areas that were preferentially activated by images of objects compared with their scrambled versions. Whereas visual cortex did not show a preference, areas associated with spatial navigation were preferentially activated by visual objects. Electrophysiological recordings in postsubiculum, the cortical head direction (HD) system hub, confirmed a preference for visual objects in both HD cells and fast-spiking interneurons. In freely moving animals, visual objects increased firing rates of HD cells aligned with a visual object but decreased activity in HD cells coding for other directions.Editor’s summary Although much of the visual system is dedicated to processing objects, we still don’t fully understand how visual objects affect spatial information coding. Siegenthaler et al . used functional ultrasound imaging to screen for mouse brain areas strongly activated by visual objects. At the brain network level, the spatial navigation system, not the ventral visual stream as in primates, exhibited a robust preference for visual objects. At the brain region level, one of the top hits of the ultrasound screen was the postsubiculum, an area with many head direction cells. In recordings from postsubiculum cells in freely moving mice, visual objects boosted the firing rate of head direction cells, with preferred firing directions pointing toward the object, and decreased the firing of cells that encoded other head directions. —Peter SternINTRODUCTION In our day-to-day life, we use visual objects (e.g., a specific clock tower when walking around town, etc.) as spatial landmarks to help orientate ourselves as we make our way through the world. We can use visual objects as spatial landmarks because our brains dedicate considerable computational power toward parsing the world into objects. Moreover, our location in the world is processed by specialized cells such as place cells, grid cells, and head direction (HD) cells in the brain’s spatial navigation system. However, much remains unknown about how visual objects modulate tuning properties of the neurons that encode spatial variables, partly because it is unclear how visual objects are processed in the rodent brain, where spatial navigation signals have been most extensively studied. RATIONALE To address this gap in knowledge, we reasoned that a brainwide activity screen in mice could identify visual object–preferring areas in an unbiased way. Using electrophysiology, we then characterized the spatial correlates of individual neurons in the areas responding to objects in freely moving mice. RESULTS Our brainwide screen based on functional ultrasound imaging revealed that spatial navigation–related areas, not visual cortical areas, tended to show a preference for visual objects. The postsubiculum, a hub of the HD system, exhibited the strongest object preference. In head-fixed conditions, we discovered that HD cells were differentially modulated by visual stimulation based on their preferred firing direction: HD cells pointing toward the visual stimulus were excited, whereas HD cells pointing away from the visual stimulus were inhibited. The same modulation was observed in freely moving conditions, when an object was displayed in the environment. CONCLUSION Visual objects refine the population encoding of HD in the postsubiculum by increasing the response of HD cells that code toward the object while simultaneously decreasing the firing rate of HD cells that code directions away from the object. As an analogy, imagine yourself wandering around a city with a compass (which, in our experiments, is the brain’s HD system), and each time you look at a landmark (which, in our experiments, is an image of an object), the compass needle becomes more stable and thus more accurate. Together, these results provide insights into how the brain uses visual landmarks to dynamically enhance the encoding of spatial information about the world. Visual objects sharpen the representation of head direction. Of all visually responsive regions, the most object-preferring areas belonged to the spatial navigation system. Electrophysiological analysis in one of the identified regions, the postsubiculum, indicated that when an animal faces a visual landmark, HD encoding is refined. W, west; N, north; E, east; S, south. [Three-dimensional brain images prepared with cocoframer © 2018 Allen Institute for Brain Science. Allen Brain Explorer]Animals use visual objects to guide navigation-related behaviors. However, visual object–preferring areas have yet to be described in the mouse brain, limiting our understanding of how visual objects affect spatial navigation system processing. Using functional ultrasound imaging, we identified brain areas that were preferentially activated by images of objects compared with their scrambled versions. Whereas visual cortex did not show a preference, areas associated with spatial navigation were preferentially activated by visual objects. Electrophysiological recordings in postsubiculum, the cortical head direction (HD) system hub, confirmed a preference for visual objects in both HD cells and fast-spiking interneurons. In freely moving animals, visual objects increased firing rates of HD cells aligned with a visual object but decreased activity in HD cells coding for other directions.Editor’s summary Although much of the visual system is dedicated to processing objects, we still don’t fully understand how visual objects affect spatial information coding. Siegenthaler et al . used functional ultrasound imaging to screen for mouse brain areas strongly activated by visual objects. At the brain network level, the spatial navigation system, not the ventral visual stream as in primates, exhibited a robust preference for visual objects. At the brain region level, one of the top hits of the ultrasound screen was the postsubiculum, an area with many head direction cells. In recordings from postsubiculum cells in freely moving mice, visual objects boosted the firing rate of head direction cells, with preferred firing directions pointing toward the object, and decreased the firing of cells that encoded other head directions. —Peter SternINTRODUCTION In our day-to-day life, we use visual objects (e.g., a specific clock tower when walking around town, etc.) as spatial landmarks to help orientate ourselves as we make our way through the world. We can use visual objects as spatial landmarks because our brains dedicate considerable computational power toward parsing the world into objects. Moreover, our location in the world is processed by specialized cells such as place cells, grid cells, and head direction (HD) cells in the brain’s spatial navigation system. However, much remains unknown about how visual objects modulate tuning properties of the neurons that encode spatial variables, partly because it is unclear how visual objects are processed in the rodent brain, where spatial navigation signals have been most extensively studied. RATIONALE To address this gap in knowledge, we reasoned that a brainwide activity screen in mice could identify visual object–preferring areas in an unbiased way. Using electrophysiology, we then characterized the spatial correlates of individual neurons in the areas responding to objects in freely moving mice. RESULTS Our brainwide screen based on functional ultrasound imaging revealed that spatial navigation–related areas, not visual cortical areas, tended to show a preference for visual objects. The postsubiculum, a hub of the HD system, exhibited the strongest object preference. In head-fixed conditions, we discovered that HD cells were differentially modulated by visual stimulation based on their preferred firing direction: HD cells pointing toward the visual stimulus were excited, whereas HD cells pointing away from the visual stimulus were inhibited. The same modulation was observed in freely moving conditions, when an object was displayed in the environment. CONCLUSION Visual objects refine the population encoding of HD in the postsubiculum by increasing the response of HD cells that code toward the object while simultaneously decreasing the firing rate of HD cells that code directions away from the object. As an analogy, imagine yourself wandering around a city with a compass (which, in our experiments, is the brain’s HD system), and each time you look at a landmark (which, in our experiments, is an image of an object), the compass needle becomes more stable and thus more accurate. Together, these results provide insights into how the brain uses visual landmarks to dynamically enhance the encoding of spatial information about the world. Visual objects sharpen the representation of head direction. Of all visually responsive regions, the most object-preferring areas belonged to the spatial navigation system. Electrophysiological analysis in one of the identified regions, the postsubiculum, indicated that when an animal faces a visual landmark, HD encoding is refined. W, west; N, north; E, east; S, south. [Three-dimensional brain images prepared with cocoframer © 2018 Allen Institute for Brain Science. Allen Brain Explorer
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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