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Full-Text Articles in Physiology

Clique Topology Reveals Intrinsic Geometric Structure In Neural Correlations, Chad Giusti, Eva Pastalkova, Carina Curto, Vladimir Itskov Jan 2015

Clique Topology Reveals Intrinsic Geometric Structure In Neural Correlations, Chad Giusti, Eva Pastalkova, Carina Curto, Vladimir Itskov

Department of Mathematics: Faculty Publications

Detecting meaningful structure in neural activity and connectivity data is challenging in the presence of hidden nonlinearities, where traditional eigenvalue-based methods may be misleading. We introduce a novel approach to matrix analysis, called clique topology, that extracts features of the data invariant under nonlinear monotone transformations. These features can be used to detect both random and geometric structure, and depend only on the relative ordering of matrix entries. We then analyzed the activity of pyramidal neurons in rat hippocampus, recorded while the animal was exploring a 2D environment, and confirmed that our method is able to detect geometric organization using …


Critical Flicker Frequency In A Harp Seal, Pagophilus Groenlandicus (Erxleben, 1777), Charles D. Bernholz Jan 1973

Critical Flicker Frequency In A Harp Seal, Pagophilus Groenlandicus (Erxleben, 1777), Charles D. Bernholz

UNL Libraries: Faculty Publications

Critical flicker frequency (CFF) in a free-swimming harp seal (Pagophilus groenlandicus) was investigated using behavioral techniques. The resulting CFF versus intensity contour indicates a definite rod-cone break, confirming a duplex photoreceptor population whose presence had not been observed in previous morphological reports.