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Frankfurt am Main, Germany

Yue X.,Massachusetts General Hospital | Biederman I.,University of Southern California | Mangini M.C.,Concordia College | Malsburg C.V.D.,Frankfurt Institute of Advanced Studies | Amir O.,University of Southern California
Vision Research | Year: 2012

Shape representation is accomplished by a series of cortical stages in which cells in the first stage (V1) have local receptive fields tuned to contrast at a particular scale and orientation, each well modeled as a Gabor filter. In succeeding stages, the representation becomes largely invariant to Gabor coding (Kobatake & Tanaka, 1994). Because of the non-Gabor tuning in these later stages, which must be engaged for a behavioral response (Tong, 2003; Tong et al., 1998), a V1-based measure of shape similarity based on Gabor filtering would not be expected to be highly correlated with human performance when discriminating complex shapes (faces and teeth-like blobs) that differ metrically on a two-choice, match-to-sample task. Here we show that human performance is highly correlated with Gabor-based image measures (Gabor simple and complex cells), with values often in the mid 0.90s, even without discounting the variability in the speed and accuracy of performance not associated with the similarity of the distractors. This high correlation is generally maintained through the stages of HMAX, a model that builds upon the Gabor metric and develops units for complex features and larger receptive fields. This is the first report of the psychophysical similarity of complex shapes being predictable from a biologically motivated, physical measure of similarity. As accurate as these measures were for accounting for metric variation, a simple demonstration showed that all were insensitive to viewpoint invariant (nonaccidental) differences in shape. © 2012 Elsevier Ltd. Source

Phillips W.A.,University of Stirling | Phillips W.A.,Frankfurt Institute of Advanced Studies
Behavioral and Brain Sciences | Year: 2013

Life is preserved and enhanced by coordinated selectivity in local neural circuits. Narrow receptive-field selectivity is necessary to avoid the curse-of-dimensionality, but local activities can be made coherent and relevant by guiding learning and processing using broad coordinating contextual gain-controlling interactions. Better understanding of the functions and mechanisms of those interactions is therefore crucial to the issues Clark examines. © 2013 Cambridge University Press. Source

Zhi Q.,TU Darmstadt | Zhi Q.,Helmholtz Center for Heavy Ion Research | Zhi Q.,Guizhou Normal University | Caurier E.,University of Strasbourg | And 7 more authors.
Physical Review C - Nuclear Physics | Year: 2013

We have performed large-scale shell-model calculations of the half-lives and neutron-branching probabilities of the r-process waiting-point nuclei at the magic neutron numbers N=50, 82, and 126. The calculations include contributions from allowed Gamow-Teller and first-forbidden transitions. We find good agreement with the measured half-lives for the N=50 nuclei with charge numbers Z=28-32 and for the N=82 nuclei 129Ag and 130Cd. The contribution of forbidden transitions reduce the half-lives of the N=126 waiting-point nuclei significantly, while they have only a small effect on the half-lives of the N=50 and 82 r-process nuclei. © 2013 American Physical Society. Source

Van Hees H.,Goethe University Frankfurt | Van Hees H.,Frankfurt Institute of Advanced Studies
European Journal of Physics | Year: 2014

In this comment, we demonstrate that the example of a DC-conducting wire of finite length as an example for the application of the Biot-Savart law is flawed due to the non-conservation of electric charge for such an unphysical setting. The implications drawn in [1] on the restrictions of Ampères circuital law in integral form are unnecessary as long as only physically realizable situations obeying the charge-conservation law are considered. © 2014 IOP Publishing Ltd. Source

Chandrapala T.N.,Hong Kong University of Science and Technology | Shi B.E.,Hong Kong University of Science and Technology | Triesch J.,Frankfurt Institute of Advanced Studies
5th Joint International Conference on Development and Learning and Epigenetic Robotics, ICDL-EpiRob 2015 | Year: 2015

Neural development in the visual cortex depends on the visual experience during the so-called critical period. Recent experiments have shown that under normal conditions rodents develop binocular receptive fields which have similar orientation preferences for the left and right eyes. In contrast, under conditions of monocular deprivation during the critical period, this orientation alignment does not happen. Here we propose a computational model to explain the process of orientation alignment, its underlying mechanisms, and its failure in case of monocular deprivation or uncorrelated binocular inputs. Our model is based on the recently proposed Active Efficient Coding framework that jointly develops eye movement control and sensory representations. Our model suggests that the active maintenance of a binocular visual field, which leads to correlated visual inputs from the two eyes, is essential for the process of orientation alignment. This behavior is analogous to vergence control in primates. However, due to the fact that rodents have large receptive fields with low spatial frequency tuning, the coordination of the eyes need not be very precise. The model also suggests that it is not necessary that coordinated binocular vision be maintained continuously in order for orientation alignment to develop. © 2015 IEEE. Source

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