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Rat primary auditory cortex is tuned exclusively to the contralateral hemifield

JOURNAL OF NEUROPHYSIOLOGY 2013年第9期110卷 2140-2151页

作者： Yao, Justin D. Bremen, Peter Middlebrooks, John C. Univ Calif Irvine Dept Neurobiol & Behav Irvine CA 92697 USA Univ Calif Irvine Dept Otolaryngol Irvine CA 92697 USA Univ Calif Irvine Ctr Hearing Res Irvine CA 92697 USA Univ Calif Irvine Dept Cognit Sci Irvine CA 92697 USA Univ Calif Irvine Dept Biomed Engn Irvine CA 92697 USA

The rat is a widely used species for study of the auditory system. Psychophysical results from rats have shown an inability to discriminate sound source locations within a lateral hemifield, despite showing fairly sharp near-midline acuity. We tested the hypothesis that those characteristics of the rat's sound localization psychophysics are evident in the characteristics of spatial sensitivity of its cortical neurons. In addition, we sought quantitative descriptions of in vivo spatial sensitivity of cortical neurons that would support development of an in vitro experimental model to study cortical mechanisms of spatial hearing. We assessed the spatial sensitivity of single- and multiple-neuron responses in the primary auditory cortex (A1) of urethane-anesthetized rats. Free-field noise bursts were varied throughout 360 degrees of azimuth in the horizontal plane at sound levels from 10 to 40 dB above neural thresholds. All neurons encountered in A1 displayed contralateral-hemifield spatial tuning in that they responded strongly to contralateral sound source locations, their responses cut off sharply for locations near the frontal midline, and they showed weak or no responses to ipsilateral sources. Spatial tuning was quite stable across a 30-dB range of sound levels. Consistent with rat psychophysical results, a linear discriminator analysis of spike counts exhibited high spatial acuity for near-midline sounds and poor discrimination for off-midline locations. Hemifield spatial tuning is the most common pattern across all mammals tested previously. The homogeneous population of neurons in rat area A1 will make an excellent system for study of the mechanisms underlying that pattern.

关键词： neural coding level-invariant coding anesthetized rat sound localization spatial hearing

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Impact and sources of neuronal variability in the fly's motion vision pathway

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JOURNAL OF PHYSIOLOGY-PARIS 2013年第1-2期107卷 26-40页

作者： Warzecha, Anne-Kathrin Rosner, Ronny Grewe, Jan Univ Bielefeld Dept Neurobiol D-33619 Bielefeld Germany Univ Marburg D-35032 Marburg Germany Univ Munich Dept Biol 2 D-82152 Martinsried Germany

Nervous systems encode information about dynamically changing sensory input by changes in neuronal activity. Neuronal activity changes, however, also arise from noise sources within and outside the nervous system or from changes of the animal's behavioral state. The resulting variability of neuronal responses in representing sensory stimuli limits the reliability with which animals can respond to stimuli and may thus even affect the chances for survival in certain situations. Relevant sources of noise arising at different stages along the motion vision pathway have been investigated from the sensory input to the initiation of behavioral reactions. Here, we concentrate on the reliability of processing visual motion information in flies. Flies rely on visual motion information to guide their locomotion. They are among the best established model systems for the processing of visual motion information allowing us to bridge the gap between behavioral performance and underlying neuronal computations. It has been possible to directly assess the consequences of noise at major stages of the fly's visual motion processing system on the reliability of neuronal signals. Responses of motion sensitive neurons and their variability have been related to optomotor movements as indicators for the overall performance of visual motion computation. We address whether and how noise already inherent in the stimulus, e.g. photon noise for the visual system, influences later processing stages and to what extent variability at the output level of the sensory system limits behavioral performance. Recent advances in circuit analysis and the progress in monitoring neuronal activity in behaving animals should now be applied to understand how the animal meets the requirements of fast and reliable manoeuvres in naturalistic situations. (C) 2012 Elsevier Ltd. All rights reserved.

关键词： Motion vision Optomotor behavior Neuronal variability Fly neural coding Insect

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Linking dynamical and functional properties of intrinsically bursting neurons

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JOURNAL OF COMPUTATIONAL NEUROSCIENCE 2013年第2期35卷 213-230页

作者： Samengo, Ines Mato, German Elijah, Daniel H. Schreiber, Susanne Montemurro, Marcelo A. Ctr Atom Bariloche San Carlos De Bariloche Rio Negro Argentina Inst Balseiro San Carlos De Bariloche Rio Negro Argentina Univ Manchester Fac Life Sci Manchester M13 9PT Lancs England Humboldt Univ Dept Biol Berlin Germany BCCN Berlin Berlin Germany

Several studies have shown that bursting neurons can encode information in the number of spikes per burst: As the stimulus varies, so does the length of individual *** stimuli, however, vary substantially among different sensory modalities and different *** goal of this paper is to determine which kind of stimulus features can be encoded in burst length, and how those features depend on the mathematical properties of the underlying dynamical *** show that the initiation and termination of each burst is triggered by specific stimulus features whose temporal characteristsics are determined by the types of bifurcations that initiate and terminate firing in each burst. As only a few bifurcations are possible, only a restricted number of encoded features exists. Here we focus specifically on describing parabolic, square-wave and elliptic bursters. We find that parabolic bursters, whose firing is initiated and terminated by saddle-node bifurcations, behave as prototypical integrators: Firing is triggered by depolarizing stimuli, and lasts for as long as excitation is prolonged. Elliptic bursters, contrastingly, constitute prototypical resonators, since both the initiating and terminating bifurcations possess well-defined oscillation time scales. Firing is therefore triggered by stimulus stretches of matching frequency and terminated by a phase-inversion in the oscillation. The behavior of square-wave bursters is somewhat intermediate, since they are triggered by a fold bifurcation of cycles of well-defined frequency but are terminated by a homoclinic bifurcation lacking an oscillating time scale. These correspondences show that stimulus selectivity is determined by the type of bifurcations. By testing several neuron models, we also demonstrate that additional biological properties that do not modify the bifurcation structure play a minor role in stimulus encoding. Moreover, we show that burst-length variability (and thereby, the capacity to

关键词： Bursts neural coding Dynamical systems Bifurcations Covariance analysis

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Synchronous firing of antennal-lobe projection neurons encodes the behaviorally effective ratio of sex-pheromone components in male Manduca sexta

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JOURNAL OF COMPARATIVE PHYSIOLOGY A-NEUROETHOLOGY SENSORY neural AND BEHAVIORAL PHYSIOLOGY 2013年第11期199卷 963-979页

作者： Martin, Joshua P. Lei, Hong Riffell, Jeffrey A. Hildebrand, John G. Case Western Reserve Univ Dept Biol Cleveland OH 44106 USA Univ Arizona Dept Neurosci Tucson AZ 85721 USA Univ Washington Dept Biol Seattle WA 98195 USA

Olfactory stimuli that are essential to an animal's survival and reproduction are often complex mixtures of volatile organic compounds in characteristic proportions. Here, we investigated how these proportions are encoded in the primary olfactory processing center, the antennal lobe, of male Manduca sexta moths. Two key components of the female's sex pheromone, present in an approximately 2:1 ratio, are processed in each of two neighboring glomeruli in the macroglomerular complex (MGC) of males of this species. In wind-tunnel flight experiments, males exhibited behavioral selectivity for ratios approximating the ratio released by conspecific females. The ratio between components was poorly represented, however, in the firing-rate output of uniglomerular MGC projection neurons (PNs). PN firing rate was mostly insensitive to the ratio between components, and individual PNs did not exhibit a preference for a particular ratio. Recording simultaneously from pairs of PNs in the same glomerulus, we found that the natural ratio between components elicited the most synchronous spikes, and altering the proportion of either component decreased the proportion of synchronous spikes. The degree of synchronous firing between PNs in the same glomerulus thus selectively encodes the natural ratio that most effectively evokes the natural behavioral response to pheromone.

关键词： Olfaction neural coding Glomerulus Pheromone neural synchrony

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Normalization is a general neural mechanism for context-dependent decision making

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PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA 2013年第15期110卷 6139-6144页

作者： Louie, Kenway Khaw, Mel W. Glimcher, Paul W. NYU Ctr Neural Sci New York NY 10003 USA

Understanding the neural code is critical to linking brain and behavior. In sensory systems, divisive normalization seems to be a canonical neural computation, observed in areas ranging from retina to cortex and mediating processes including contrast adaptation, surround suppression, visual attention, and multisensory integration. Recent electrophysiological studies have extended these insights beyond the sensory domain, demonstrating an analogous algorithm for the value signals that guide decision making, but the effects of normalization on choice behavior are unknown. Here, we show that choice models using normalization generate significant (and classically irrational) choice phenomena driven by either the value or number of alternative options. In value-guided choice experiments, both monkey and human choosers show novel context-dependent behavior consistent with normalization. These findings suggest that the neural mechanism of value coding critically influences stochastic choice behavior and provide a generalizable quantitative framework for examining context effects in decision making.

关键词： context dependence divisive normalization neural coding neuroeconomics reward

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Distribution in time and space of linked spikes in closed neural circuits of the sensorimotor cortex in the rabbit (a rhythmic defensive dominant)

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Neuroscience and Behavioral Physiology 2013年第5期43卷 543-550页

作者： Galashina, A.G. Bogdanov, A.V. Institute of Higher Nervous Activity and Neurophysiology Russian Academy of Sciences Moscow Russian Federation

Analysis of linked spike activity in simultaneously recorded neurons in the rabbit sensorimotor cortex identified 22 closed neural circuits consisting of three or four neurons. In experiments using a model of a defensive dominant, the distribution of linked spikes was analyzed in real time 1-3 weeks after imposition of a rhythmic (2 sec) activity on the rabbit. The analysis showed that events in which linked spikes in neuron pairs arose with 2-sec intervals could be displaced in time and space in one direction along the closed neuron circuit. Two-second intervals between linked spikes in neighboring pairs could be "conjugated," i.e., the end of one interval in one pair was beginning of the 2-sec interval in the neighboring pair. "Conjugated" intervals of neighboring pairs could promote "pass-though" of information relating to the properties of the stimulus via the closed neuron circuit, thus completing a complete cycle of passage of the information through it. There could be several such cycles in a period of 1 min. The longest "passthrough" transfers lasted 10-12 sec. Complex variants of information transmission were identified, with not only pass-through transfers of the 2-sec interval from one neuron pair to another, but also repeat occurrences of linked spikes with this interval in any of the pairs constituting the circuit being analyzed. The longest transfers lasted 16 and 22 sec. © 2013 Springer Science+Business Media New York.

关键词： dominant focus multineuron activity neural coding neural networks rabbits sensorimotor cortex

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Comparing neural coding of auditory in bat and vestibular in rat

Comparing neural coding of auditory in bat and vestibular in...

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中国神经科学学会第四次会员代表大会暨第八届全国学术会议

作者： Yong-Kui ZHANG Research Center for Learning Science School of Biological Sciences and Medical EngineeringSoutheast University

＜正＞This report summarize my experimental data on auditory and vestibular *** mammal,one inner ear has two functions:auditory and *** sensor and motor information mechanical are transformed by hair cells. Auditory neural code in lower frequency firing rate but processed with several nucleus pathway steps before reach auditory cortex,showing higher non-linear coding but keep tonotopic *** improve information processing, cortico-fugal feedback pathway modulating auditory neural activity of inferior colliculus in *** the other hand, vestibular neural coding in higher firing rate,showing linear coding and short downward reflex *** postnatal development data in rat vestibular afferent were present.

关键词： auditory vestibular neural coding computational neuroscience

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Bayesian entropy estimation for countable discrete distributions

The Journal of Machine Learning Research

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The Journal of Machine Learning Research 2014年第1期15卷

作者： Kevin Murphy Bernhard Schölkopf Evan Archer Il Memming Park Jonathan W. Pillow Google Center for Perceptual Systems The University of Texas at Austin Austin TX and Max Planck Institute for Biological Cybernetics Tübingen Germany Center for Perceptual Systems The University of Texas at Austin Austin TX Department of Psychology Section of Neurobiology Division of Statistics and Scientific Computation and Center for Perceptual Systems The University of Texas at Austin Austin TX

We consider the problem of estimating Shannon's entropy H from discrete data, in cases where the number of possible symbols is unknown or even countably infinite. The Pitman-Yor process, a generalization of Dirichlet process, provides a tractable prior distribution over the space of countably infinite discrete distributions, and has found major applications in Bayesian non-parametric statistics and machine learning. Here we show that it provides a natural family of priors for Bayesian entropy estimation, due to the fact that moments of the induced posterior distribution over H can be computed analytically. We derive formulas for the posterior mean (Bayes' least squares estimate) and variance under Dirichlet and Pitman-Yor process priors. Moreover, we show that a fixed Dirichlet or Pitman-Yor process prior implies a narrow prior distribution over H, meaning the prior strongly determines the entropy estimate in the under-sampled regime. We derive a family of continuous measures for mixing Pitman-Yor processes to produce an approximately flat prior over H. We show that the resulting "Pitman-Yor Mixture" (PYM) entropy estimator is consistent for a large class of distributions. Finally, we explore the theoretical properties of the resulting estimator, and show that it performs well both in simulation and in application to real data.

关键词： Bayesian estimation Bayesian nonparametrics Dirichlet process Pitman-Yor process entropy information theory neural coding

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Modeling the generation of output by the cerebellar nuclei

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neural NETWORKS 2013年 47卷 112-119页

作者： Steuber, Volker Jaeger, Dieter Univ Hertfordshire Sci & Technol Res Inst Hatfield AL10 9AB Herts England Emory Univ Dept Biol Atlanta GA 30030 USA

Functional aspects of network integration in the cerebellar cortex have been studied experimentally and modeled in much detail ever since the early work by theoreticians such as Man, Albus and Braitenberg more than 40 years ago. In contrast, much less is known about cerebellar processing at the output stage, namely in the cerebellar nuclei (CN). Here, input from Purkinje cells converges to control CN neuron spiking via GABAergic inhibition, before the output from the CN reaches cerebellar targets such as the brainstem and the motor thalamus. In this article we review modeling studies that address how the CN may integrate cerebellar cortical inputs, and what kind of signals may be transmitted. Specific hypotheses in the literature contrast rate coding and temporal coding of information in the spiking output from the CN. One popular hypothesis states that post-inhibitory rebound spiking may be an important mechanism by which Purkinje cell inhibition is turned into CN output spiking, but this hypothesis remains controversial. Rate coding clearly does take place, but in what way it may be augmented by temporal codes remains to be more clearly established. Several candidate mechanisms distinct from rebound spiking are discussed, such as the significance of spike time correlations between Purkinje cell pools to determine CN spike timing, irregularity of Purkinje cell spiking as a determinant of CN firing rate, and shared brief pauses between Purkinje cell pools that may trigger individual CN spikes precisely. (C) 2012 Elsevier Ltd. All rights reserved.

关键词： Purkinje cell neural coding STD Rebound Compartmental model Dynamic clamp

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neural variability, or lack thereof

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FRONTIERS IN COMPUTATIONAL NEUROSCIENCE 2013年第2013期7卷 7-7页

作者： Masquelier, Timothee Univ Pompeu Fabra Unit Brain & Cognit Dept Informat & Commun Technol Barcelona Spain Univ Paris 06 CNRS Lab Neurobiol Adapt Proc UMR 7102 Paris France

We do not claim that the brain is completely deterministic, and we agree that noise may be beneficial in some cases. But we suggest that neuronal variability may be often overestimated, due to uncontrolled internal variables, and/or the use of inappropriate reference times. These ideas are not new, but should be re-examined in the light of recent experimental findings: trial-to-trial variability is often correlated across neurons, across trials, greater for higher-order neurons, and reduced by attention, suggesting that "intrinsic" sources of noise can only account for a minimal part of it. While it is obviously difficult to control for all internal variables, the problem of reference time can be largely avoided by recording multiple neurons at the same time, and looking at statistical structures in relative latencies. These relative latencies have another major advantage: they are insensitive to the variability that is shared across neurons, which is often a significant part of the total variability. Thus, we suggest that signal-to-noise ratios in the brain may be much higher than usually thought, leading to reactive systems, economic in terms of number of neurons, and energy efficient.

关键词： neural variability signal-to-noise ratio reliability redundancy neural coding

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