1,720,963 research outputs found
Learning substrates in the primate prefrontal cortex and striatum: sustained activity related to successful actions
No full textLearning from experience requires knowing whether a past action resulted in a desired outcome. The prefrontal cortex and basal ganglia are thought to play key roles in such learning of arbitrary stimulus-response associations. Previous studies have found neural activity in these areas, similar to dopaminergic neurons' signals, that transiently reflect whether a response is correct or incorrect. However, it is unclear how this transient activity, which fades in under a second, influences actions that occur much later. Here, we report that single neurons in both areas show sustained, persistent outcome-related responses. Moreover, single behavioral outcomes influence future neural activity and behavior: behavioral responses are more often correct and single neurons more accurately discriminate between the possible responses when the previous response was correct. These long-lasting signals about trial outcome provide a way to link one action to the next and may allow reward signals to be combined over time to implement successful learning
Neural encoding of object properties and task-dependent changes in primate visual area V4
Full text linkThesis (Ph.D.)--University of Washington, 2017Primates use vision to understand and interact with the world around them. Several interconnected visual areas are responsible for processing information about visual objects, ultimately enabling object and scene recognition and perception. Visual area V4 is an intermediate stage in the pathway of object processing, and V4 neurons are sensitive to multiple aspects of objects such as their form, texture, and color. The first goal of this dissertation was to investigate how responses of neurons in visual area V4 reflect information about object boundaries and interiors. Unlike prominent computational models of object recognition which rely on boundaries, the majority of neurons in area V4 displayed a modulation of responses by the presence or absence of an object interior. I developed two computational model modifications that successfully incorporated both of the response characteristics that I observed experimentally: sensitivity to boundaries and sensitivity to the presence of an object interior. The second goal of this dissertation was to examine whether V4 response selectivity for shape and color of visual objects depended on the task which the animal was performing. I compared responses during a task where the animal was discriminating object shape to a task where the animal was passively viewing the same objects. I found that the majority of neurons displayed not only a change in the magnitude of responses between the two tasks, but that response changes were additionally dependent on object shape and color. Together, these studies contribute to our understanding of how neurons encode visual information, and how this encoding is changed during behavior
The role of V4 in object motion processing
No full textThesis (Master's)--University of Washington, 2023We rely heavily on our visual system for many functions. More specifically, the ability to process and track moving objects is of utmost importance. Much of the literature and conventional teachings in neuroscience hypothesize that the visual system has two functionally distinct pathways: a dorsal visual pathway for motion processing and a ventral visual pathway for form processing. However, this functional dichotomy is slowly eroding – specifically, many neurons along the ventral visual pathway demonstrate the ability to process the motion of objects. We focused our attention on ventral visual area V4, the most interconnected visual area of the visual system. We sought to understand how motion processing in V4 contrasts and complements motion processing in key dorsal stream areas, such as areas MT and MST. Many studies have shown the critical role that the dorsal visual stream plays in processing and perceiving motion information yet gaps remain in our knowledge of visual information. We find that neurons in V4 show selectivity for the motion of objects, rather than motion behind an aperture (i.e., V4 neurons preferentially encode the motion of stimuli with explicit boundaries translating across the visual field rather than static stimuli). These results demonstrate a novel and complementary motion processing mechanism in the ventral stream
Dataset: Dissociation in neuronal encoding of object versus surface motion in the primate brain
No full textDissociation in neuronal encoding of object versus surface motion in the primate brainAnthony Bigelow⤉, Taekjun Kim⤉, Tomoyuki Namima, Wyeth Bair, Anitha PasupathyCurrent Biology (in press, 2023)If you publish any work using the data, please cite the publication above (Bigelow et al., 2023), and also cite the data set using the following:Bigelow, Anthony; Kim, Taekjun; Namima, Tomoyuki; Bair, Wyeth; Pasupathy, Anitha (2022), “Dataset: Dissociation in neuronal encoding of object versus surface motion in the primate brain”, Mendeley Data, V1, doi: 10.17632/cs76nk38zj.1THIS DATASET IS ARCHIVED AT DANS/EASY, BUT NOT ACCESSIBLE HERE. TO VIEW A LIST OF FILES AND ACCESS THE FILES IN THIS DATASET CLICK ON THE DOI-LINK ABOV
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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