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The Representation of Visual Naturalistic Stimuli in Resting State Activity: An Investigation in the Visual and Motor Areas Representations at Rest
Get PDFResting state is characterized as an offline period, during which the
eyes may be either open or closed. In this disengaged state, one’s
system operates independently of external input or feedback, and by
definition, relies on an internalized model of the world. Literature
shows that resting state activity may reflect the statistics of the natural
environment, but also the unique individual biases, and is possible to
be reshaped over time. This is highlighted by studies that show that
resting state fluctuations maintain traces of everyday activity; but how
are these representations extracted, how stable are they, and to what
extent are they malleable? To answer that we need to understand: 1)
How is our system structured to maintain regularities? 2) How are they
integrated in an internalized model? 3) How do low frequencies
fluctuate when detecting an error? The main aim of this thesis is to
understand how natural information is represented in resting state. The
working model is that (1) naturalistic information is processed along a
hierarchy in time and space to code higher level information that is low
dimensional and sparse (chapter 2). 2) This information is then
maintained in resting state in a generic form (chapter 3). 3) This is
achieved because low frequency fluctuations are adapted to naturalistic
statics, and hence are altered in otherwise unexpected situations
(chapter 4). We examined the functional connectivity (FC) of MEG
signal changes in the visual (VIS) and dorsal attention (DAN) networks
during the observation of naturalistic videos, by comparing them to a
pretrained convolutional network. We reveal distinct temporal
dynamics in processing low and high-level features. Low-level features
are immediately and abundantly represented, while high-level features
exhibit a delayed and scarce representation, potentially storing
information in a generic form (chapter 2). For instance, we find that the
BOLD multivoxel spatial representation of a still hand, controlled for
low-level features, is coherent with the spatial representation of the
resting somatomotor area, as opposed to another object such as a food
item (chapter 3). We suggest that the representations during resting
states may contribute to the goal of interacting with the environment.
This is enriched by our final findings; the multivoxel spatial
representation of observing common movements aligns more
coherently with resting somatomotor patterns as opposed to
uncommon (chapter 4)
Encoding of common grasps in the resting human brain
No full textIntroduction:
An abundant literature shows similarities between task-driven and intrinsic (low frequency
fluctuations(LFFs)/ resting state) driven activity. But how exactly do task-related functional
connectivity (FC) of LFFs get modulated, and what is the significance of this information? Newest
resting state literature suggests that the brain at rest preserves representations of the statistical
regularities of the body and the natural environment (Livne, 2020; Pezzulo et al., 2021; Betti et
al., 2021). For example, recent findings suggest a higher similarity between resting state and
task-evoked fluctuation patterns and patterns elicited by common hand movements as opposed
to uncommon (Livne, 2020). Accordingly, in a previous work, we show that the resting
somatomotor cortex retains the topography of the hand and that that effect is mediated by use
(El Rassi, 2022). Here we test the hypothesis that watching motor execution performed in a
common/naturalistic way has a similar FC architecture to that of resting state LFFs. We expect that visual task related modulations of LFF FC will be more pronounced than when observing nonnaturalistic
actions. This is based on literature showing that action observation excites similar
networks as action execution, and that that excitation is facilitated when observing naturalistic
movements (Lago, 2010). Here we take it one step forward and investigate visual task
modulations with respect to resting state architecture. In particular we hypothesize that 1)
functional connectivity architecture is different when observing common hand grasps vs
uncommon, and 2) modulations related to watching common hand grasps are more correlated to
resting state fluctuations that code regularities of the environment, as opposed to viewing
uncommon hand grasps.
Methods:
We collected 15 minutes of resting state fMRI data and then asked our participants to watch
videos of common and uncommon (tilted shoulder, elbow and fingers) hand grasps of 26 subjects,
organized in blocks (30 s blocks, including 10 videos each). All data was preprocessed using SPM,
and subject-specific whole brain ROI to ROI LFF functional connectivity matrices were generated
for the resting state block and each category, using Conn toolbox. We used the parcellation of
Conn toolbox of the whole brain ending up with 32 main nodes with 496 connections. We first
performed a t-test contrasting common and uncommon FC matrices. We then computed for each
subject the correlation between FC patterns at rest and in each of our 2 conditions. Finally, we
performed a t-test between the correlations of rest and task.
Results:
Results: We found 1) significant differences in connectivity between common and uncommon
conditions in 48 nodes (p<0.05, uncorrected) and a general increase of functional connectivity
when watching uncommon vs common movements. Of interest, the biggest clusters with FC
differences were between the visual system and the sensorimotor and dorsal attention networks,
2) a higher correlation of FC between rest and common movement viewing as opposed to
uncommon (p=0.002)
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Get PDFWe 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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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