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Background noise exerts diverse effects on the cortical encoding of foreground sounds

JOURNAL OF NEUROPHYSIOLOGY 2017年第2期118卷 1034-1054页

作者： Malone, B. J. Heiser, Marc A. Beitel, Ralph E. Schreiner, Christoph E. Univ Calif San Francisco Dept Otolaryngol Head & Neck Surg Coleman Mem Lab 675 Nelson Rising LnRm 535 San Francisco CA 94143 USA Univ Calif Los Angeles Dept Psychiat Div Adolescent & Child Semel Inst Neurosci & Behav Los Angeles CA USA Univ Calif San Francisco Dept Otolaryngol Head & Neck Surg Ctr Integrat Neurosci San Francisco CA USA Univ Calif San Francisco Dept Bioengn San Francisco CA 94143 USA Univ Calif San Francisco Dept Therapeut Sci San Francisco CA 94143 USA Univ Calif San Francisco Dept Physiol San Francisco CA 94143 USA

In natural listening conditions, many sounds must be detected and identified in the context of competing sound sources, which function as background noise. Traditionally, noise is thought to degrade the cortical representation of sounds by suppressing responses and increasing response variability. However, recent studies of neural network models and brain slices have shown that background synaptic noise can improve the detection of signals. Because acoustic noise affects the synaptic background activity of cortical networks, it may improve the cortical responses to signals. We used spike train decoding techniques to determine the functional effects of a continuous white noise background on the responses of clusters of neurons in auditory cortex to foreground signals, specifically frequency-modulated sweeps (FMs) of different velocities, directions, and amplitudes. Whereas the addition of noise progressively suppressed the FM responses of some cortical sites in the core fields with decreasing signal-to-noise ratios (SNRs), the stimulus representation remained robust or was even significantly enhanced at specific SNRs in many others. Even though the background noise level was typically not explicitly encoded in cortical responses, significant information about noise context could be decoded from cortical responses on the basis of how the neural representation of the foreground sweeps was affected. These findings demonstrate significant diversity in signal in noise processing even within the core auditory fields that could support noise-robust hearing across a wide range of listening conditions. NEW & NOTEWORTHY The ability to detect and discriminate sounds in background noise is critical for our ability to communicate. The neural basis of robust perceptual performance in noise is not well understood. We identified neuronal populations in core auditory cortex of squirrel monkeys that differ in how they process foreground signals in background noise and that may contrib

关键词： auditory cortex hearing neural coding noise

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Optimal nonlinear cue integration for sound localization

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JOURNAL OF COMPUTATIONAL NEUROSCIENCE 2017年第1期42卷 37-52页

作者： Fischer, Brian J. Pena, Jose Luis Seattle Univ Dept Math 901 12th Ave Seattle WA 98122 USA Albert Einstein Coll Med Dept Neurosci 1410 Pelham Pkwy South Bronx NY 10461 USA

Integration of multiple sensory cues can improve performance in detection and estimation tasks. There is an open theoretical question of the conditions under which linear or nonlinear cue combination is Bayes-optimal. We demonstrate that a neural population decoded by a population vector requires nonlinear cue combination to approximate Bayesian inference. Specifically, if cues are conditionally independent, multiplicative cue combination is optimal for the population vector. The model was tested on neural and behavioral responses in the barn owl's sound localization system where space-specific neurons owe their selectivity to multiplicative tuning to sound localization cues interaural phase (IPD) and level (ILD) differences. We found that IPD and ILD cues are approximately conditionally independent. As a result, the multiplicative combination selectivity to IPD and ILD of midbrain space-specific neurons permits a population vector to perform Bayesian cue combination. We further show that this model describes the owl's localization behavior in azimuth and elevation. This work provides theoretical justification and experimental evidence supporting the optimality of nonlinear cue combination.

关键词： Cue combination Bayesian inference neural coding Sound localization Barn owl Population code

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Feedback Synthesizes neural Codes for Motion

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CURRENT BIOLOGY 2017年第9期27卷 1356-1361页

作者： Clarke, Stephen E. Maler, Leonard Univ Ottawa Dept Cellular & Mol Med 451 Smyth Rd Ottawa ON K1H 8M5 Canada Univ Ottawa Brain & Mind Inst 451 Smyth Rd Ottawa ON K1H 8M5 Canada Univ Ottawa Ctr Neural Dynam 451 Smyth Rd Ottawa ON K1H 8M5 Canada

In senses as diverse as vision, hearing, touch, and the electrosense, sensory neurons receive bottom-up input from the environment, as well as top-down input from feedback loops involving higher brain regions [1-4]. Through connectivity with local inhibitory interneurons, these feedback loops can exert both positive and negative control over fundamental aspects of neural coding, including bursting [5, 6] and synchronous population activity [7, 8]. Here we show that a prominent midbrain feedback loop synthesizes a neural code for motion reversal in the hindbrain electrosensory ON-and OFF-type pyramidal cells. This top-down mechanism generates an accurate bidirectional encoding of object position, despite the inability of the electrosensory afferents to generate a consistent bottom-up representation [9, 10]. The net positive activity of this midbrain feedback is additionally regulated through a hindbrain feedback loop, which reduces stimulus-induced bursting and also dampens the ON and OFF cell responses to interfering sensory input [11]. We demonstrate that synthesis of motion representations and cancellation of distracting signals are mediated simultaneously by feedback, satisfying an accepted definition of spatial attention [12]. The balance of excitatory and inhibitory feedback establishes a "focal'' distance for optimized neural coding, whose connection to a classic motion-tracking behavior provides new insight into the computational roles of feedback and active dendrites in spatial localization [13, 14].

关键词： top-down processing topographic feedback neural coding burst spiking spatial attention motion tracking ON and OFF cells electric fish cerebellum gain control

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Decoding sound level in the marmoset primary auditory cortex

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JOURNAL OF NEUROPHYSIOLOGY 2017年第4期118卷 2024-2033页

作者： Sun, Wensheng Marongelli, Ellisha N. Watkins, Paul V. Barbour, Dennis L. Washington Univ Dept Biomed Engn One Brookings Dr St Louis MO 63130 USA

Neurons that respond favorably to a particular sound level have been observed throughout the central auditory system, becoming steadily more common at higher processing areas. One theory about the role of these level-tuned or nonmonotonic neurons is the level-invariant encoding of sounds. To investigate this theory, we simulated various subpopulations of neurons by drawing from real primary auditory cortex (A1) neuron responses and surveyed their performance in forming different sound level representations. Pure nonmonotonic subpopulations did not provide the best level-invariant decoding;instead, mixtures of monotonic and nonmonotonic neurons provided the most accurate decoding. For level-fidelity decoding, the inclusion of nonmonotonic neurons slightly improved or did not change decoding accuracy until they constituted a high proportion. These results indicate that nonmonotonic neurons fill an encoding role complementary to, rather than alternate to, monotonic neurons. NEW & NOTEWORTHY Neurons with nonmonotonic rate-level functions are unique to the central auditory system. These level-tuned neurons have been proposed to account for invariant sound perception across sound levels. Through systematic simulations based on real neuron responses, this study shows that neuron populations perform sound encoding optimally when containing both monotonic and nonmonotonic neurons. The results indicate that instead of working independently, nonmonotonic neurons complement the function of monotonic neurons in different sound-encoding contexts.

关键词： primate auditory cortex neural coding sound pressure level encoding nonmonotonic

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Taste input from tarsal sensilla is related to egg-laying behavior in Papilio hospiton

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ENTOMOLOGIA EXPERIMENTALIS ET APPLICATA 2017年第1期165卷 38-49页

作者： Sollai, Giorgia Biolchini, Maurizio Loy, Francesco Solari, Paolo Crnjar, Roberto Univ Cagliari Dept Biomed Sci I-09042 Monserrato CA Italy

In herbivorous insects, host selection involves various sensory modalities (sight, smell, taste), but the contact chemoreceptors capable of detecting stimuli both from host and non-host plants play an important role in the final steps of oviposition behavior. Female butterflies scratch and drum the leaf surface and taste the compounds present in plant saps with their tarsal chemosensilla. We assumed that tarsal taste sensitivity may be related to the breadth of host selection in ovipositing females of Papilio hospitonGene (Lepidoptera: Papilionidae). The spike activity of tarsal taste basiconic sensilla was recorded in response to stimulation with NaCl, bitter compounds, and carbohydrates, with the aim of characterizing the gustatory receptor neurons (GRNs) and of comparing the response patterns in the light of differences in acceptability of host plants. Then we studied the sensitivity of GRNs to saps of the host plants Ferula communis L., Peucedanum paniculatumLoisel, Pastinaca latifolia (Duby) DC. (all Apiaceae), and Ruta lamarmorae Bacch., Brullo et Giusso (Rutaceae), and evaluated the relationship between taste sensitivity and oviposition preference. The results indicate that (1) each sensillum houses sugar-, bitter-, and salt-sensitive cells;(2) the spike activity of the gustatory neurons in response to plant saps produces a different response pattern across all active GRNs;and (3) the number of eggs laid on each plant is highest on *** and lowest on ***. These results suggest that the varying activity of the tarsal GRNs may affect host plant acceptability and that ovipositing females of *** seem to be able to discriminate between host plants.

关键词： chemoreception host plant selection oviposition Papilionidae neural coding Lepidoptera

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Multiplexed Spike coding and Adaptation in the Thalamus

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CELL REPORTS 2017年第6期19卷 1130-1140页

作者： Mease, Rebecca A. Kuner, Thomas Fairhall, Adrienne L. Groh, Alexander Tech Univ Munich Dept Neurosurg D-81675 Munich Germany Univ Washington Neurobiol & Behav Grad Program Seattle WA 98195 USA Heidelberg Univ Dept Funct Neuroanat D-69120 Heidelberg Germany Univ Washington Dept Physiol & Biophys Seattle WA 98195 USA

High-frequency "burst'' clusters of spikes are a generic output pattern of many neurons. While bursting is a ubiquitous computational feature of different nervous systems across animal species, the encoding of synaptic inputs by bursts is not well understood. We find that bursting neurons in the rodent thalamus employ "multiplexing'' to differentially encode low-and high-frequency stimulus features associated with either T-typecalcium "low-threshold'' or fast sodium spiking events, respectively, and these events adapt differently. Thus, thalamic bursts encode disparate information in three channels: (1) burst size, (2) burst onset time, and (3) precise spike timing within bursts. Strikingly, this latter "intraburst'' encoding channel shows millisecond-level feature selectivity and adapts across statistical contexts to maintain stable information encoded per spike. Consequently, calcium events both encode low-frequency stimuli and, in parallel, gate a transient window for high-frequency, adaptive stimulus encoding by sodium spike timing, allowing bursts to efficiently convey fine-scale temporal information.

关键词： neural coding linear-nonlinear model adaptation thalamocortical system bursting T-type calcium channel excitability multiplexing

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Cholinergic shaping of neural correlations

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PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA 2017年第22期114卷 5725-5730页

作者： Minces, Victor Pinto, Lucas Dan, Yang Chiba, Andrea A. Univ Calif San Diego Dept Cognit Sci La Jolla CA 92093 USA Univ Calif Berkeley Howard Hughes Med Inst Helen Wills Neurosci Inst Div NeurobiolDept Mol & Cell Biol Berkeley CA 94720 USA Univ Calif San Diego Program Neurosci La Jolla CA 92093 USA Princeton Univ Princeton Neurosci Inst Princeton NJ 08544 USA

A primary function of the brain is to form representations of the sensory world. Its capacity to do so depends on the relationship between signal correlations, associated with neuronal receptive fields, and noise correlations, associated with neuronal response variability. It was recently shown that the behavioral relevance of sensory stimuli can modify the relationship between signal and noise correlations, presumably increasing the encoding capacity of the brain. In this work, we use data from the visual cortex of the awake mouse watching naturalistic stimuli and show that a similar modification is observed under heightened cholinergic modulation. Increasing cholinergic levels in the cortex through optogenetic stimulation of basal forebrain cholinergic neurons decreases the dependency that is commonly observed between signal and noise correlations. Simulations of correlated neural networks with realistic firing statistics indicate that this change in the correlation structure increases the encoding capacity of the network.

关键词： acetylcholine neural coding neural correlations neuromodulation sensory processing

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Spontaneous Activity in the Zebrafish Tectum Reorganizes over Development and Is Influenced by Visual Experience

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CURRENT BIOLOGY 2017年第16期27卷 2407-+页

作者： Avitan, Lilach Pujic, Zac Molter, Jan Van de Poll, Matthew Sun, Biao Teng, Haotian Amor, Rumelo Scott, Ethan K. Goodhill, Geoffrey J. Univ Queensland Queensland Brain Inst Brisbane Qld 4072 Australia Univ Queensland Sch Math & Phys Brisbane Qld 4072 Australia Univ Queensland Sch Biomed Sci Brisbane Qld 4072 Australia

Spontaneous patterns of activity in the developing visual system may play an important role in shaping the brain for function. During the period 4-9 dpf (days post-fertilization), larval zebrafish learn to hunt prey, a behavior that is critically dependent on the optic tectum. However, how spontaneous activity develops in the tectum over this period and the effect of visual experience are unknown. Here we performed two-photon calcium imaging of GCaMP6s zebrafish larvae at all days from 4 to 9 dpf. Using recently developed graph theoretic techniques, we found significant changes in both single-cell and population activity characteristics over development. In particular, we identified days 5-6 as a critical moment in the reorganization of the underlying functional network. Altering visual experience early in development altered the statistics of tectal activity, and dark rearing also caused a long-lasting deficit in the ability to capture prey. Thus, tectal development is shaped by both intrinsic factors and visual experience.

关键词： neural coding neural assemblies neural plasticity visual development critical period calcium imaging graph theory prey capture dark rearing behavior

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Synaptic Mechanisms of Feature coding in the Visual Cortex of Awake Mice

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NEURON 2017年第5期95卷 1147-+页

作者： Adesnik, Hillel Univ Calif Berkeley Dept Mol & Cell Biol Berkeley CA 94720 USA Univ Calif Berkeley Helen Wills Neurosci Inst Berkeley CA 94720 USA

The synaptic mechanisms of feature coding in the visual cortex are poorly understood, particularly in awake animals. The ratio between excitation (E) and inhibition (I) might be constant across stimulus space, controlling only the gain and timing of neuronal responses, or it might change, directly contributing to feature coding. Whole-cell recordings in L2/3 of awake mice revealed that the E/I ratio systematically declines with increasing stimulus contrast or size. Suppressing somatostatin (SOM) neurons enhanced the E and I underlying size tuning, explaining SOM neurons' role in surround suppression. These data imply that contrast and size tuning result from a combination of a changing E/I ratio and the tuning of total synaptic input. Furthermore, they provide experimental support in awake animals for the "Stabilized Supralinear Network," a model that explains diverse cortical phenomena, and suggest that a decreasing E/I ratio with increasing cortical drive could contribute to many different cortical computations.

关键词： Primary visual cortex V1 E/I balance size tuning normalization contextual modulation optogenetics in vivo whole cell contrast sensitivity neural coding

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Active Touch and Self-Motion Encoding by Merkel Cell-Associated Afferents

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NEURON 2017年第3期94卷 666-+页

作者： Severson, Kyle S. Xu, Duo Van de Loo, Margaret Bai, Ling Ginty, David D. O'Connor, Daniel H. Johns Hopkins Univ Sch Med Solomon H Snyder Dept Neurosci Brain Sci InstKavli Neurosci Discovery Inst Baltimore MD 21205 USA Harvard Med Sch Howard Hughes Med Inst Dept Neurobiol 220 Longwood Ave Boston MA 02115 USA Johns Hopkins Univ Sch Med Neurosci Training Program Baltimore MD 21205 USA

Touch perception depends on integrating signals from multiple types of peripheral mechanoreceptors. Merkel-cell associated afferents are thought to play a major role in form perception by encoding surface features of touched objects. However, activity of Merkel afferents during active touch has not been directly measured. Here, we show that Merkel and unidentified slowly adapting afferents in the whisker system of behaving mice respond to both self-motion and active touch. Touch responses were dominated by sensitivity to bending moment (torque) at the base of the whisker and its rate of change and largely explained by a simple mechanical model. Self-motion responses encoded whisker position within a whisk cycle (phase), not absolute whisker angle, and arose from stresses reflecting whisker inertia and activity of specific muscles. Thus, Merkel afferents send to the brain multiplexed information about whisker position and surface features, suggesting that proprioception and touch converge at the earliest neural level.

关键词： neural coding barrel cortex primary afferents proprioception whisker system somatosensation perception reafferent active sensation sensorimotor integration

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