1,721,001 research outputs found
Brain modeling of noun representations in sighted and blind individuals
No full textComputational modeling for neural decoding of activation patterns in blight and sighted subject
The case for preregistering all region of interest (ROI) analyses in neuroimaging research
No full textIn neuroimaging studies, small sample sizes and the resultant reduced statistical power to detect effects that are not large, combined with inadequate analytic choices, concur to produce inflated or false-positive findings. To mitigate these issues, researchers often restrict analyses to specific brain areas, using the region of interest (ROI) approach. Crucially, ROI analysis assumes the a priori justified definition of the target region. Nonetheless, reports often lack details about where in the timeline, ranging from study conception to the data analysis and interpretation of findings, were ROIs selected. Frequently, the rationale for ROI selection is vague or inadequately founded on the existing literature. These shortcomings have important implications for ROI-based studies, augmenting the risk that observed effects are inflated or even false positives. Tools like preregistration and registered reports could address this problem, ensuring the validity of ROI-based studies. The benefits could be enhanced by additional practices such as selection of ROIs using quantitative methods (i.e., meta-analysis) and the sharing of whole-brain unthresholded maps of effect size, as well as of binary ROIs, in publicly accessible repositories
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
Ventral and Dorsal Stream Dissociation During Action Recognition in the Human Brain.
No full textIntroduction. According to the perception-action framework [4], the ventral stream mediates object recognition, while the dorsal stream processes the sensory control of object-directed actions. The existence of two functionally independent visual streams [3], however, is debated [8]. To determine whether such a pure functional dissociation exists, or rather an integration of action-object representations occurs in the ventral and dorsal streams, we used a Multi Voxel Pattern Analysis to examine whether neural patterns of visually perceived hand-mediated actions differed on the basis of the object class being manipulated.
Methods. We used an fMRI (Philips 3T; TR 2.5s; 3x3x3 mm voxel size) six-run slow event-related design to examine neural activity in 14 right-handed healthy volunteers while they watched 3s-long videos that randomly alternated between different types of human hand-made, object-directed actions or environmental scenes with 7s of ISI. A first set of stimuli depicted ‘tool-mediated’ (e.g. hammering a nail, cutting with scissors), ‘intransitive’ (e.g. clapping, ok gesture) and ‘distal transitive’ (e.g. opening a jar, grabbing) actions. A second set consisted of videos reproducing three fixed motor acts (‘pushing away’, ‘grasping-to-lift’, ‘putting down’) performed with ‘animate’ and ‘inanimate’ objects. After standard processing using AFNI [1], BOLD responses to each stimulus of the first set were used in a 3-class Support Vector Machine (SVM) classifier [6] with an additional Recursive Feature Elimination algorithm [2]. Then, the discriminative voxels of this classifier responding to action features were isolated into ventral occipito-temporal [5] and dorsal parietal regions of interest (ROIs). Inside these ROIs, the patterns of BOLD response elicited by the second set of action stimuli were compared to each other and to those elicited by environmental scenes to obtain a representational dissimilarity matrix (RDM) using the 1-r Pearson coefficient [7]. A hierarchical clustering procedure was derived from the RDM to create a dendrogram. Moreover, we used multi-class SVM classifiers to assess the uncertainty in cluster analysis. Accuracy (Acc) values of the classifiers were tested as significantly different from chance by a permutation test.
Results. The SVM classifier, trained on the first set of stimuli, was able to distinguish between ‘tool-mediated’, ‘intransitive’ and ‘distal transitive’ actions with an Acc of 73.3% (p<0.0025). The discriminative map [Fig 1] relied on an inferior frontal, premotor, inferior parietal and temporal cortical network, and included brain areas mainly within the human mirror system [9]. Using the second set of actions, as expected, environmental scenes were clearly separated from actions in both ROIs (Acc 92%, p<0.0025). Within the inferior temporal ROI, the RDM showed a significant distinction between the two classes of objects only (‘animate’ vs. ‘inanimate’, Acc 69.7%, p<0.0025) but was unable to recognize the different actions [Fig 2]. Using the parietal ROI, we found a significant distinction between three classes of actions (‘pushing’ vs. ‘grasping’ vs. ‘putting’ acts, Acc 39.8%, p<0.05) and between the two classes of objects (‘animate’ vs. ‘inanimate’, Acc 58.3%, p<0.05) [Fig 3].
Conclusions. In line with previous findings [7], action stimuli were processed in the ventral stream accordingly to the recognition of object features (specifically, ‘animate’ and ‘inanimate’ properties), even when the represented object was included within more complex action scenes. The dorsal stream was able to discriminate both different classes of motor acts and object features, suggesting a more complex analysis of the relationship between objects and actions. In conclusion, our results suggest that the functional dissociation between the ventral and dorsal streams may be less absolute than previously thought, as the dorsal stream appears to be able to respond to object features as well.
1 Cox R.W. (1996), ‘AFNI: software for analysis and visualization of functional magnetic resonance neuroimages’, Computers And Biomedical Research, vol. 29, pp. 162-173.
2 De Martino F. (2008), ‘Combining multivariate voxel selection and support vector machines for mapping and classification of fMRI spatial patterns’, Neuroimage vol 43, pp. 44-58.
3 Fang, F. (2005), ‘Cortical responses to invisible objects in the human dorsal and ventral pathways’, Nature Neuroscience, vol. 8, pp. 1380–1385.
4 Goodale, M. A. (1992), ‘Separate visual pathways for perception and action’, Trends in Neurosciences, vol. 15, pp. 20–25.
5 Haxby, J.V. (2001), ‘Distributed and overlapping representations of faces and objects in ventral temporal cortex’, Science vol. 293, pp. 2425-2430.
6 Joachims T. (1999), ‘Making large-Scale SVM Learning Practical. Advances in Kernel Methods - Support Vector Learning’, MIT Press, 1999.
7 Kriegeskorte N. (2008), ‘Matching categorical object representations in inferior temporal cortex of man and monkey’, Neuron, vol. 60, pp.1126–41.
8 Mahon, B.Z. (2007), ‘Action-related properties shape object representations in the ventral stream’, Neuron, vol. 55, pp. 507–520.
9 Ricciardi E. (2009), ‘Do we really need vision? How blind people "see" the actions of others’, The Journal of Neuroscience, vol. 29, pp. 9719-9724
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
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
- …
