zaterdag 27 oktober 2012

Bilateral Theta-Burst TMS to Influence Global Gestalt Perception

 
 

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via PLoS ONE Alerts: Neuroscience door Bernd Ritzinger et al. op 26-10-12

by Bernd Ritzinger, Elisabeth Huberle, Hans-Otto Karnath

While early and higher visual areas along the ventral visual pathway in the inferotemporal cortex are critical for the recognition of individual objects, the neural representation of human perception of complex global visual scenes remains under debate. Stroke patients with a selective deficit in the perception of a complex global Gestalt with intact recognition of individual objects – a deficit termed simultanagnosia – greatly helped to study this question. Interestingly, simultanagnosia typically results from bilateral lesions of the temporo-parietal junction (TPJ). The present study aimed to verify the relevance of this area for human global Gestalt perception. We applied continuous theta-burst TMS either unilaterally (left or right) or bilateral simultaneously over TPJ. Healthy subjects were presented with hierarchically organized visual stimuli that allowed parametrical degrading of the object at the global level. Identification of the global Gestalt was significantly modulated only for the bilateral TPJ stimulation condition. Our results strengthen the view that global Gestalt perception in the human brain involves TPJ and is co-dependent on both hemispheres.

 
 

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dinsdag 23 oktober 2012

Open evaluation: a vision for entirely transparent post-publication peer rev...

 
 

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per pubmed: top authors autorius Kriegeskorte N 12.10.23

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Open evaluation: a vision for entirely transparent post-publication peer review and rating for science.

Front Comput Neurosci. 2012;6:79

Authors: Kriegeskorte N

Abstract
The two major functions of a scientific publishing system are to provide access to and evaluation of scientific papers. While open access (OA) is becoming a reality, open evaluation (OE), the other side of the coin, has received less attention. Evaluation steers the attention of the scientific community and thus the very course of science. It also influences the use of scientific findings in public policy. The current system of scientific publishing provides only journal prestige as an indication of the quality of new papers and relies on a non-transparent and noisy pre-publication peer-review process, which delays publication by many months on average. Here I propose an OE system, in which papers are evaluated post-publication in an ongoing fashion by means of open peer review and rating. Through signed ratings and reviews, scientists steer the attention of their field and build their reputation. Reviewers are motivated to be objective, because low-quality or self-serving signed evaluations will negatively impact their reputation. A core feature of this proposal is a division of powers between the accumulation of evaluative evidence and the analysis of this evidence by paper evaluation functions (PEFs). PEFs can be freely defined by individuals or groups (e.g., scientific societies) and provide a plurality of perspectives on the scientific literature. Simple PEFs will use averages of ratings, weighting reviewers (e.g., by H-index), and rating scales (e.g., by relevance to a decision process) in different ways. Complex PEFs will use advanced statistical techniques to infer the quality of a paper. Papers with initially promising ratings will be more deeply evaluated. The continual refinement of PEFs in response to attempts by individuals to influence evaluations in their own favor will make the system ungameable. OA and OE together have the power to revolutionize scientific publishing and usher in a new culture of transparency, constructive criticism, and collaboration.

PMID: 23087639 [PubMed - in process]


 
 

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"ViSA: A neurodynamic model for visuo-spatial working memory, attentional bl...

 
 

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via Psychological Review - Vol 119, Iss 4 by Simione, Luca; Raffone, Antonino; Wolters, Gezinus; Salmas, Paola; Nakatani, Chie; Belardinelli, Marta Olivetti; van Leeuwen, Cees on 10/22/12

Reports an error in "ViSA: A Neurodynamic Model for Visuo-Spatial Working Memory, Attentional Blink, and Conscious Access" by Luca Simione, Antonino Raffone, Gezinus Wolters, Paola Salmas, Chie Nakatani, Marta Olivetti Belardinelli and Cees van Leeuwen ( Psychological Review, Advanced Online Publication, Jul 23, 2012, np). The article was published online missing the link to the supplemental materials. The link to the supplemental materials is provided in the erratum. (The following abstract of the original article appeared in record 2012-19411-001.) Two separate lines of study have clarified the role of selectivity in conscious access to visual information. Both involve presenting multiple targets and distracters: one simultaneously in a spatially distributed fashion, the other sequentially at a single location. To understand their findings in a unified framework, we propose a neurodynamic model for Visual Selection and Awareness (ViSA). ViSA supports the view that neural representations for conscious access and visuo-spatial working memory are globally distributed and are based on recurrent interactions between perceptual and access control processors. Its flexible global workspace mechanisms enable a unitary account of a broad range of effects: It accounts for the limited storage capacity of visuo-spatial working memory, attentional cueing, and efficient selection with multi-object displays, as well as for the attentional blink and associated sparing and masking effects. In particular, the speed of consolidation for storage in visuo-spatial working memory in ViSa is not fixed but depends adaptively on the input and recurrent signaling. Slowing down of consolidation due to weak bottom-up and recurrent input as a result of brief presentation and masking leads to the attentional blink. Thus, ViSA goes beyond earlier 2-stage and neuronal global workspace accounts of conscious processing limitations. (PsycINFO Database Record (c) 2012 APA, all rights reserved)

 
 

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ViSA: A neurodynamic model for visuo-spatial working memory, attentional bli...

 
 

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via Psychological Review - Vol 119, Iss 4 by Simione, Luca; Raffone, Antonino; Wolters, Gezinus; Salmas, Paola; Nakatani, Chie; Belardinelli, Marta Olivetti; van Leeuwen, Cees on 7/23/12

[Correction Notice: An Erratum for this article was reported in Vol 119(4) of Psychological Review (see record 2012-27828-002). The article was published online missing the link to the supplemental materials. The link to the supplemental materials is provided in the erratum.] Two separate lines of study have clarified the role of selectivity in conscious access to visual information. Both involve presenting multiple targets and distracters: one simultaneously in a spatially distributed fashion, the other sequentially at a single location. To understand their findings in a unified framework, we propose a neurodynamic model for Visual Selection and Awareness (ViSA). ViSA supports the view that neural representations for conscious access and visuo-spatial working memory are globally distributed and are based on recurrent interactions between perceptual and access control processors. Its flexible global workspace mechanisms enable a unitary account of a broad range of effects: It accounts for the limited storage capacity of visuo-spatial working memory, attentional cueing, and efficient selection with multi-object displays, as well as for the attentional blink and associated sparing and masking effects. In particular, the speed of consolidation for storage in visuo-spatial working memory in ViSA is not fixed but depends adaptively on the input and recurrent signaling. Slowing down of consolidation due to weak bottom-up and recurrent input as a result of brief presentation and masking leads to the attentional blink. Thus, ViSA goes beyond earlier 2-stage and neuronal global workspace accounts of conscious processing limitations. (PsycINFO Database Record (c) 2012 APA, all rights reserved)

 
 

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Bistable Gestalts reduce activity in the whole of V1, not just the retinotop...

 
 

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via Journal of Vision recent issues by de-Wit, L. H., Kubilius, J., Wagemans, J., Op de Beeck, H. P. on 10/22/12

Abstract Activity in the primary visual cortex reduces when certain stimuli can be perceptually organized as a unified Gestalt. This reduction could offer important insights into the nature of feedback computations within the human visual system; however, the properties of this response reduction have not yet been investigated in detail. Here we replicate this reduced V1 response, but find that the modulation in V1 (and V2) to the perceived organization of the input is not specific to the retinotopic location at which the sensory input from that stimulus is represented. Instead, we find a response modulation that is equally evident across the primary visual cortex. Thus in contradiction to some models of hierarchical predictive coding, the perception of an organized Gestalt causes a broad feedback effect that does not act specifically on the part of the retinotopic map representing the sensory input.

 
 

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vrijdag 19 oktober 2012

The beauty of being wrong: A plea for post-publication revision


 
 
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The beauty of being wrong: A plea for post-publication revision

I realize that most of what I will ever write as a scientist is wrong. Not because it is obviously wrong when I write it, or because I don't believe in my own research. But simply because virtually every insight is eventually replaced by some newer and generally more accurate insight. This is true even for the great theories of the likes of Darwin, Einstein, and Newton. And it is certainly true for the minor contributions of the remaining 99.99% of the research population, for whom supersession generally occurs quite rapidly.

Unfortunately, there are no such signs in science

Perhaps this sounds depressing, but it's really not. It's just a (negative) way of describing progress. It's a good thing. Scientists should be encouraged to acknowledge the wrongness of their theories, to find out what's so wrong about them, and to replace them by newer theories that are still wrong, but less so. You could even argue that the possibility of being wrong is what differentiates science from opinionist fields such as philosophy, art, and economics.

But the ideal model of a scientist who continually seeks to disprove himself is not very compatible with human nature. Being human after all, scientists hate to be proven wrong, and will go through great lengths (including plain denial) to avoid this from happening. Nevertheless, given a healthy environment, scientists can, to some extent, overcome their innate dislike of being wrong. But only given a healthy scientific environment. And this is, in my opinion, where things go, well... wrong.

Lately, there has been much ado about reforms of academic publishing. Most of the debate has focused on the slow, but steady shift towards open access models (i.e. making scientific papers publicly accessible). I'm a big proponent of open access, but I also think that there are deeper problems that go beyond copyright issues. More specifically, I think that the way in which scientific results are presented is detrimental to a healthy scientific climate.


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