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Independence or non-negativity: Constraints for sensory coding

International Congress Series 2004年第C期1269卷 38-41页

作者： Choi, Seungjin Department of Computer Science POSTECH Pohang 790-784 San 31 Hyoja-dong Nam-gu South Korea

This paper addresses two different coding strategies in the framework of linear generative models. One relies on statistical independence between encoding variables and the other imposes non-negativity constraints in both basis functions and encoding variables. These lead to holistic or parts-based representation. We stress out some useful behaviour of parts-based representation and introduce a new way of information representation, which exhibits holistic structure as well as parts-based representation together. © 2004 Elsevier B.V.

关键词： Holistic representation Independent component analysis Nonnegative matrix factorization Parts-based representation sensory coding Sparse coding

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Storing and restoring visual input with collaborative rank coding and associative memory

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NEUROCOMPUTING 2006年第1-12期69卷 1219-1223页

作者： Rehn, M Sommer, FT Royal Inst Technol KTH NADA SE-10044 Stockholm Sweden Univ Calif Berkeley Redwood Ctr Theoret Neurosci Berkeley CA 94720 USA

Associative memory in cortical circuits has been held as a major mechanism for content-addressable memory. Hebbian synapses implement associative memory efficiently when storing sparse binary activity patterns. However, in models of sensory processing, representations are graded and not binary. Thus, it has been an unresolved question how sensory computation could exploit cortical associative memory. Here we propose a way how sensory processing could benefit from memory in cortical circuitry. We describe a new collaborative method of rank coding for converting graded stimuli, such as natural images, into sequences of synchronous spike volleys. Such sequences of sparse binary patterns can be efficiently processed in associative memory of the Willshaw type. We evaluate storage capacity and noise tolerance of the proposed system and demonstrate its use in cleanup and fill-in for noisy or occluded visual input. (c) 2006 Elsevier B.V. All rights reserved.

关键词： sensory coding attractor memory rank coding sequence memory data compression

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Receptive fields of simple cells from a taxonomic study of natural images and suppression of scale redundancy

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NEUROCOMPUTING 2006年第10-12期69卷 1224-1227页

作者： Delgado, Jose M. Turiel, Antonio Parga, Nestor Univ Autonoma Madrid Dept Fis Teor E-28049 Madrid Spain

Much effort has been carried out to propose models of the early visual pathway based on the statistical analysis of natural images. These conventional frameworks lead to predictions on the RFs of simple cells which do not fit well their observed properties [D.L. Ringach, Spatial structure and symmetry of simple-cell receptive fields in macaque primary visual cortex, J. Neurophysiol. 2002 (2002) 455-463]. In order to overcome these difficulties, we have been carrying a research program to derive robust coding principles from the statistics of natural images [A. Turiel, G. Mato, N. Parga, J.P. Nadal, Self-similarity properties of natural images, in: Proceedings of NIPS'97, vol. 10, MIT Press, 1997, pp. 836-842;A. Turiel, J.M. Delgado, N. Parga, Learning efficient internal representations from natural image collections, Neurocomputing 58-60 (2004) 915-921]. Two principles emerging from our study of image statistics are: first, there exists scale redundancy and this can be eliminated from the code;second, images are constructed by a combination (partly linear and partly non-linear) of some simple patterns of contrast (edges, bars, and composites of these two). These two principles can be used to derive filters which explain observed properties of the RFs of simple cells and which compare quite well with the results reported by Ringach [Spatial structure and symmetry of simple-cell receptive fields in macaque primary visual cortex, J. Neurophysiol. 2002 (2002) 455-463] and previous experimental work. (c) 2006 Elsevier B.V. All rights reserved.

关键词： sensory coding learning feature detectors natural images

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Trpm5 null mice respond to bitter, sweet, and umami compounds

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CHEMICAL SENSES 2006年第3期31卷 253-264页

作者： Damak, S Rong, MQ Yasumatsu, K Kokrashvili, Z Pérez, CA Shigemura, N Yoshida, R Mosinger, B Glendinning, JI Ninomiya, Y Margolskee, RF Mt Sinai Sch Med Dept Neurosci New York NY 10029 USA Mt Sinai Sch Med Dept Physiol & Biophys New York NY 10029 USA Kyushu Univ Sect Oral Neurosci Higashi Ku Fukuoka 8128582 Japan Columbia Univ Barnard Coll Dept Biol Sci New York NY 10027 USA

Trpm5 is a calcium-activated cation channel expressed selectively in taste receptor cells. A previous study reported that mice with an internal deletion of Trpm5, lacking exons 15-19 encoding transmembrane segments 1-5, showed no taste-mediated responses to bitter, sweet, and umami compounds. We independently generated knockout mice null for Trpm5 protein expression due to deletion of Trpm5's promoter region and exons 1-4 (including the translation start site). We examined the taste-mediated responses of Trpm5 null mice and wild-type (WT) mice using three procedures: gustatory nerve recording [chorda tympani (CT) and glossopharyngeal (NG) nerves], initial lick responses, and 24-h two-bottle preference tests. With bitter compounds, the Trpm5 null mice showed reduced, but not abolished, avoidance (as indicated by licking responses and preference ratios higher than those of WT), a normal CT response, and a greatly diminished NG response. With sweet compounds, Trpm5 null mice showed no licking response, a diminished preference ratio, and absent or greatly reduced nerve responses. With umami compounds, Trpm5 null mice showed no licking response, a diminished preference ratio, a normal NG response, and a greatly diminished CT response. Our results demonstrate that the consequences of eliminating Trmp5 expression vary depending upon the taste quality and the lingual taste field examined. Thus, while Trpm5 is an important factor in many taste responses, its absence does not eliminate all taste responses. We conclude that Trpm5-dependent and Trpm5-independent pathways underlie bitter, sweet, and umami tastes.

关键词： gustation ion channel knockout mice sensory coding signal transduction taste

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Bestrophin-2 is a candidate calcium-activated chloride channel involved in olfactory transduction

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PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA 2006年第34期103卷 12929-12934页

作者： Pifferi, Simone Pascarella, Giovanni Boccaccio, Anna Mazzatenta, Andrea Gustincich, Stefano Menini, Anna Zucchelli, Silvia Scuola Int Super Studi Avanzati SISSA Sector Neurobiol I-34014 Trieste Italy Scuola Int Super Studi Avanzati SISSA Sector Neurobiol Giovanni Armenise Harvard Fdn Lab I-34012 Trieste Italy

Ca-activated Cl channels are an important component of olfactory transduction. Odor binding to olfactory receptors in the cilia of olfactory sensory neurons (OSNs) leads to an increase of intraciliary Ca concentration by Ca entry through cyclic nucleotide-gated (CNG) channels. Ca activates a Cl channel that leads to an efflux of Cl from the cilia, contributing to the amplification of the OSN depolarization. The molecular identity of this Cl channel remains elusive. Recent evidence has indicated that bestrophins are able to form Ca-activated Cl channels in heterologous systems. Here we have analyzed the expression of bestrophins in the mouse olfactory epithelium and demonstrated that only mouse bestrophin-2 (mlBest2) was expressed. Single-cell RT-PCR showed that mBest2 was expressed in OSNs but not in supporting cells. Immunohistochemistry revealed that mBest2 was expressed on the cilia of OSNs, the site of olfactory transduction, and colocalized with the main CNGA2 channel subunit. Electrophysiological properties of Ca-activated Cl currents from native channels in dendritic knob/cilia of mouse OSNs were compared with those induced by the expression of mBest2 in HEK-293 cells. We found the same anion permeability sequence, small estimated single-channel conductances, a Ca sensitivity difference of one order of magnitude, and the same side-specific blockage of the two Cl channel blockers commonly used to inhibit the odorant-induced Ca-activated Cl current in OSNs, niflumic acid, and 4-acetamido-4'-isothiocyanato-stilben-2,2'-disulfonate (SITS). Therefore, our data suggest that mBest2 is a good candidate for being a molecular component of the olfactory Ca-activated Cl channel.

关键词： ion channel olfaction olfactory sensory neurons patch-clamp sensory coding

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Role of statistical symmetries in sensory coding: an optimal scale invariant code for vision

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JOURNAL OF PHYSIOLOGY-PARIS 2003年第4-6期97卷 491-502页

作者： Turiel, A Parga, N Univ Autonoma Madrid Dept Fis Teor E-28049 Madrid Spain Inst Natl Rech Informat & Automat Air Project F-78153 Le Chesnay France

The visual system is the most studied sensory pathway, which is partly because visual stimuli have rather intuitive properties. There are reasons to think that the underlying principle ruling coding, however, is the same for vision and any other type of sensory signal, namely the code has to satisfy some notion of optimality-understood as minimum redundancy or as maximum transmitted information. Given the huge variability of natural stimuli, it would seem that attaining an optimal code is almost impossible;however, regularities and symmetries in the stimuli can be used to simplify the task: symmetries allow predicting one part of a stimulus from another, that is, they imply a structured type of redundancy. Optimal coding can only be achieved once the intrinsic symmetries of natural scenes are understood and used to the best performance of the neural encoder. In this paper, we review the concepts of optimal coding and discuss the known redundancies and symmetries that visual scenes have. We discuss in depth the only approach which implements the three of them known so far: translational invariance, scale invariance and multiscaling. Not surprisingly, the resulting code possesses features observed in real visual systems in mammals. (C) 2004 Elsevier Ltd. All rights reserved.

关键词： sensory coding vision multiscaling edge detection wavelets learning

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Genetic analysis of brain circuits underlying pheromone signaling

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ANNUAL REVIEW OF GENETICS 2006年第1期40卷 449-467页

作者： Dulac, C. Wagner, S. Harvard Univ Howard Hughes Med Inst Dept Mol & Cellular Biol Cambridge MA 02138 USA Hebrew Univ Jerusalem Dept Neurobiol IL-91904 Jerusalem Israel

Molecular approaches and genetic manipulations have provided novel insights into the processing of pheromone-mediated information by the olfactory and vomeronasal systems of mammals. We will review and discuss the specific contribution of each of the two chemosensory systems that ensure specific behavioral responses to conspecific animals.

关键词： vomeronasal olfactory pheromones accessory olfactory bulb olfactory coding sensory coding vomeronasal receptors

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Aftereffect of adaptation to Glass patterns

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VISION RESEARCH 2005年第11期45卷 1355-1363页

作者： Clifford, CWG Weston, E Univ Sydney Sch Psychol Dept Psychol Colour Form & Mot LabVisual Percept Unit Sydney NSW 2006 Australia

Our visual systems constantly adapt their representation of the environment to match the prevailing input. Adaptation phenomena provide striking examples of perceptual plasticity and offer valuable insight into the mechanisms of sensory coding. Here, we describe an aftereffect of adaptation to a spatially structured image whereby an unstructured test stimulus takes on illusory structure locally perpendicular to that or the adaptor. Objective measurement of the strength of the aftereffect for different patterns suggests a neural locus of adaptation prior to the extraction of complex form in the visual processing hierarchy, probably at the level of primary visual cortex. This view is supported by further experiments showing that the aftereffect exhibits partial interocular transfer but complete transfer across opposite contrast polarities. However, the aftereffect does show weak position invariance, suggesting that adaptation at higher levels of the visual system may also contribute to the effect. (c) 2005 Elsevier Ltd. All rights reserved.

关键词： spatial vision visual cortex psychophysics sensory coding orientation global form

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An integrated spinal cord-hindlimbs preparation for studying the role of intrinsic properties in somatosensory information processing

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JOURNAL OF NEUROSCIENCE METHODS 2005年第2期142卷 317-326页

作者： Reali, C Russo, RE Inst Invest Biol Clemente Estable Fac Ciencias Unidad Asoc Neurofisiol Montevideo 11600 Uruguay

Several studies performed using the slice in vitro technique have shown that spinal cord neurons display specialized intrinsic electrophysiological properties. However, the actual role of intrinsic properties in somatosensory processing remains unclear, mainly due to the impossibility to generate natural sensory inputs in spinal cord slices. Here, we show an integrated spinal cord-hindlimbs preparation of juvenile turtles that has the advantages of in vitro approaches and still enables natural stimulation. By making patch-clamp whole-cell recordings of both superficial and deep dorsal horn neurons in the integrated preparation, we found similar electrophysiological phenotypes as those observed in slices. Most of the cells responded to natural stimuli, had large receptive fields and were classified as wide-dynamic range neurons. Both low-threshold spikes and plateau potentials interacted with naturally evoked sensory inputs, generating complex dynamics. Furthermore, we found that the activity of the spinal cord network induced by natural stimulation modulated the excitability of plateau-generating cells. This effect was mimicked by bath application of cis-(+/-)-l-aminocyclopentane-1,3-dicarboxylic acid (ACPD), a group I glutamate metabotropic receptor agonist. Our results show that the spinal cord-hindlimbs preparation represents a valuable model to study the contribution of intrinsic properties to early stages of somatosensory information processing. (C) 2004 Elsevier B.V. All rights reserved.

关键词： spinal cord intrinsic properties dorsal horn neurons somatosensory system sensory coding integrated preparation neuromodulation turtle

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Learning efficient internal representations from natural image collections

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NEUROCOMPUTING 2004年 58卷 915-921页

作者： Turiel, A Delgado, JM Parga, N Univ Autonoma Madrid Dept Fis Teor E-28049 Madrid Spain

Learning in sensory systems takes place after a repeated exposure to the incoming signals and many ideas based on information theoretical principles have been proposed to explain the synaptic adaptation which improves the coding capabilities of sensory areas. In this paper we want to emphasize that a simple, natural learning rule can be derived from a careful treatment of image redundancies. The learning rule is used to split images into independent components which connect different resolution levels, in a nonlinear way. The result shows the biological plausibility of this coding strategy not only in the visual pathway but also in other sensory modalities. (C) 2004 Elsevier B.V. All rights reserved.

关键词： sensory coding learning feature detectors natural images

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