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PRECISE coding OF ANKLE ANGLE AND VELOCITY BY HUMAN CALF MUSCLE SPINDLES

NEUROSCIENCE 2017年第0期349卷 98-105页

作者： Peters, Ryan M. Dalton, Brian H. Blouin, Jean-Sebastien Inglis, J. Timothy Univ British Columbia Sch Kinesiol War Mem Gymnasium Room 2106081 Univ Blvd Vancouver BC V6T IZ1 Canada Univ British Columbia Okanagan Sch Hlth & Exercise Sci Kelowna BC V1V IV7 Canada Univ British Columbia Djavad Mowafaghian Ctr Brain Hlth Vancouver BC V6T IZ3 Canada Univ British Columbia Inst Comp Informat & Cognit Syst Vancouver BC V6T IZ4 Canada Univ British Columbia Int Collaborat Repair Discoveries Vancouver BC V5Z IM9 Canada

Human standing balance control requires the integration of sensory feedback to produce anticipatory, stabilizing ankle torques. However, the ability of human triceps surae muscle spindles to provide reliable sensory feedback regarding the small, slow ankle movements that occur during upright standing has recently come under question. We performed microneurography to directly record axon potentials from single muscle spindle afferents in the human triceps surae during servo-controlled movement of the ankle joint. To simuldte movements of the ankle while standing, we delivered random 90-s dorsiflexion/plantar flexion oscillations of the ankle joint, with a peak-to-peak amplitude of 0.7 degrees and frequency content below 0.5 Hz. In roughly half of the trials (46%), participants held a lowlevel, near-isometric contraction of the triceps surae muscles. We demonstrate that afferent activity in a population of muscle spindles closely reflects ankle movements at frequencies and amplitudes characteristic of human standing. Four out of five soleus spindles, and three out of seven gastrocnemius spindles coded for at least a single frequency component of anteroposterior ankle rotation. Concatenating within muscles, coherence was significantly greater for soleus spindles at all stimulus frequencies. Voluntary contraction of the parent muscle reduced spindle sensitivity, but only significantly near the mean power frequency of the stimulus (similar to 0.3 Hz). In conclusion, these results provide direct evidence that triceps surae muscle spindles are potentially capable of providing important sensory feedback for the control of human standing balance. (C) 2017 IBRO. Published by Elsevier Ltd. All rights reserved.

关键词： muscle spindles microneurography sensory coding triceps surae posture human

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Specialized Mechanosensory Nociceptors Mediating Rapid Responses to Hair Pull

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NEURON 2017年第4期95卷 944-+页

作者： Ghitani, Nima Barik, Arnab Szczot, Marcin Thompson, James H. Li, Chia Le Pichon, Claire E. Krashes, Michael J. Chesler, Alexander T. Natl Ctr Complementary & Integrat Hlth NCCIH NIH Bethesda MD 20892 USA Natl Inst Diabet & Digest & Kidney Dis NIDDK NIH Bethesda MD USA Natl Inst Child Hlth & Human Dev NICHD NIH Bethesda MD USA

The somatosensory system provides animals with the ability to detect, distinguish, and respond to diverse thermal, mechanical, and irritating stimuli. While there has been progress in defining classes of neurons underlying temperature sensation and gentle touch, less is known about the neurons specific for mechanical pain. Here, we use in vivo functional imaging to identify a class of cutaneous sensory neurons that are selectively activated by high-threshold mechanical stimulation (HTMRs). We show that their optogenetic excitation evokes rapid protective and avoidance behaviors. Unlike other nociceptors, these HTMRs are fast-conducting Ad-fibers with highly specialized circumferential endings wrapping the base of individual hair follicles. Notably, we find that Ad-HTMRs innervate unique but overlapping fields and can be activated by stimuli as precise as the pulling of a single hair. Together, the distinctive features of this class of Ad-HTMRs appear optimized for accurate and rapid localization of mechanical pain.

关键词： sensory coding peripheral nervous system mechanosensation touch nociception pain

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Monoaminergic control of brain states and sensory processing: Existing knowledge and recent insights obtained with optogenetics

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PROGRESS IN NEUROBIOLOGY 2017年第0期151卷 237-253页

作者： Lorincz, Magor L. Adamantidis, Antoine R. Univ Szeged Hungarian Acad Sci Res Grp Cellular & Network Neurophysiol Dept Physiol Anat & Neurosci H-6726 Szeged Hungary Univ Bern Inselspital Univ Hosp Dept Neurol Bern Switzerland Univ Bern Dept Clin Res DKF Bern Switzerland

Monoamines are key neuromodulators involved in a variety of physiological and pathological brain functions. Classical studies using physiological and pharmacological tools have revealed several essential aspects of monoaminergic involvement in regulating the sleep-wake cycle and influencing sensory responses but many features have remained elusive due to technical limitations. The application of optogenetic tools led to the ability of monitoring and controlling neuronal populations with unprecedented temporal precision and neurochemical specificity. Here, we focus on recent advances in revealing the roles of some monoamines in brain state control and sensory information processing. We summarize the central position of monoamines in integrating sensory processing across sleep-wake states with an emphasis on research conducted using optogenetic techniques. Finally, we discuss the limitations and perspectives of new integrated experimental approaches in understanding the modulatory mechanisms of monoaminergic systems in the mammalian brain. (C) 2016 Elsevier Ltd. All rights reserved.

关键词： Serotonin Noradrenaline Histamine Dopamine sensory coding Brain states

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Interspersed Distribution of Selectivity to Kinematic Stimulus Features in Supragranular Layers of Mouse Barrel Cortex

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CEREBRAL CORTEX 2017年第7期27卷 3782-3789页

作者： Martini, Francisco J. Molano-Mazon, Manuel Maravall, Miguel UMH CSIC Inst Neurociencias Alicante Avda Ramon & Cajal S-NCampus San Juan Sant Joan dAlacant 03550 Spain Ist Italiano Tecnol Ctr Neurosci & Cognit Syst UniTn Lab Neural Computat I-38068 Rovereto Italy Univ Sussex Sch Life Sci Sussex Neurosci Brighton E Sussex England

Neurons in the primary sensory regions of neocortex have heterogeneous response properties. The spatial arrangement of neurons with particular response properties is a key aspect of population representations and can shed light on how local circuits are wired. Here, we investigated how neurons with sensitivity to different kinematic features of whisker stimuli are distributed across local circuits in supragranular layers of the barrel cortex. Using 2-photon calcium population imaging in anesthetized mice, we found that nearby neurons represent diverse kinematic features, providing a rich population representation at the local scale. Neurons interspersed in space therefore responded differently to a common stimulus kinematic feature. Conversely, neurons with similar feature selectivity were located no closer to each other than predicted by a random distribution null hypothesis. This finding relied on defining a null hypothesis that was specific for testing the spatial distribution of tuning across neurons. We also measured how neurons sensitive to specific features were distributed relative to barrel boundaries, and found no systematic organization. Our results are compatible with randomly distributed selectivity to kinematic features, with no systematic ordering superimposed upon the whisker map.

关键词： map sensory coding somatosensory somatotopy tactile two photon vibrissae whiskers

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Variable Temporal Integration of Stimulus Patterns in the Mouse Barrel Cortex

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CEREBRAL CORTEX 2017年第3期27卷 1758-1764页

作者： Pitas, Anna Albarracin, Ana Lia Molano-Mazon, Manuel Maravall, Miguel CSIC Inst Neurociencias Alicante E-03550 Sant Joan dAlacant Spain Univ Miguel Hernandez E-03550 Sant Joan dAlacant Spain Univ Sussex Sch Life Sci Sussex Neurosci Brighton E Sussex England Univ Nacl Tucuman CSIC RA-4000 San Miguel De Tucuman Tucuman Argentina Ist Italiano Tecnol Rovereto Lab Neural Computat I-38068 Rovereto Italy

Making sense of the world requires distinguishing temporal patterns and sequences lasting hundreds of milliseconds or more. How cortical circuits integrate over time to represent specific sensory sequences remains elusive. Here we assessed whether neurons in the barrel cortex (BC) integrate information about temporal patterns of whisker movements. We performed cell-attached recordings in anesthetized mice while delivering whisker deflections at variable intervals and compared the information carried by neurons about the latest interstimulus interval (reflecting sensitivity to instantaneous frequency) and earlier intervals (reflecting integration over timescales up to several hundred milliseconds). Neurons carried more information about the latest interval than earlier ones. The amount of temporal integration varied with neuronal responsiveness and with the cortical depth of the recording site, that is, with laminar location. A subset of neurons in the upper layers displayed the strongest integration. Highly responsive neurons in the deeper layers encoded the latest interval but integrated particularly weakly. Under these conditions, BC neurons act primarily as encoders of current stimulation parameters;however, our results suggest that temporal integration over hundreds of milliseconds can emerge in some neurons within BC.

关键词： cell-attached in vivo sensory coding somatosensory vibrissae

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Sodium Taste During Sodium Appetite

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CHEMICAL SENSES 2017年第2期42卷 91-92页

作者： Norgren, Ralph Penn State Univ Coll Med Dept Neural & Behav Sci Hershey PA 17033 USA

Sodium appetite appears to be an excellent model to study the neural mechanisms of motivation. In this issue of Chemical Senses, experiments by St John ( 2016) challenge 2 hypotheses for how a systemic sodium deficit guides an animal to find and ingest more Na ions in the environment. Both hypotheses deal with modifications of the sensory neural code produced by Na+ ions on the tongue. One envisions a change in the Na+ signal amplitude. A reduction could make the strong Na+ signals less aversive;an increase, weak signals more noticeable. The other hypothesis requires no changes in the identity or amplitude of the Na+ signal, but a shift in its hedonic tone toward sweetness or reward. The results of the 3 behavioral experiments render both explanations unlikely but fail to suggest alternatives.

关键词： behavior motivation sensory coding sodium appetite

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coding and Plasticity in the Mammalian Thermosensory System

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NEURON 2016年第5期92卷 1079-1092页

作者： Yarmolinsky, David A. Peng, Yueqing Pogorzala, Leah A. Rutlin, Michael Hoon, Mark A. Zuker, Charles S. Columbia Univ Howard Hughes Med Inst Columbia Coll Phys & Surg New York NY 10032 USA Columbia Univ Dept Biochem & Mol Biophys Columbia Coll Phys & Surg New York NY 10032 USA Columbia Univ Dept Neurosci Columbia Coll Phys & Surg New York NY 10032 USA Natl Inst Dent & Craniofacial Res NIH Bethesda MD 20892 USA

Perception of the thermal environment begins with the activation of peripheral thermosensory neurons innervating the body surface. To understand how temperature is represented in vivo, we used genetically encoded calcium indicators to measure temperature-evoked responses in hundreds of neurons across the trigeminal ganglion. Our results show how warm, hot, and cold stimuli are represented by distinct population responses, uncover unique functional classes of thermosensory neurons mediating heat and cold sensing, and reveal the molecular logic for peripheral warmth sensing. Next, we examined how the peripheral somatosensory system is functionally reorganized to produce altered perception of the thermal environment after injury. We identify fundamental transformations in sensory coding, including the silencing and recruitment of large ensembles of neurons, providing a cellular basis for perceptual changes in temperature sensing, including heat hypersensitivity, persistence of heat perception, cold hyperalgesia, and cold analgesia.

关键词： sensory coding temperature representation TRP channels warmth sensing injury changes in peripheral coding

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Spatially resolved time-frequency analysis of odour coding in the insect antennal lobe

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EUROPEAN JOURNAL OF NEUROSCIENCE 2016年第6期44卷 2387-2395页

作者： Paoli, Marco Weisz, Nathan Antolini, Renzo Haase, Albrecht Univ Trento Ctr Mind Brain Sci Piazza Manifattura 1 I-38068 Rovereto Italy Salzburg Univ Div Physiol Psychol Ctr Cognit Neurosci Salzburg Austria Univ Trento Dept Phys Trento Italy

Antennal lobes constitute the first neurophils in the insect brain involved in coding and processing of olfactory information. With their stereotyped functional and anatomical organization, they provide an accessible model with which to investigate information processing of an external stimulus in a neural network invivo. Here, by combining functional calcium imaging with time-frequency analysis, we have been able to monitor the oscillatory components of neural activity upon olfactory stimulation. The aim of this study is to investigate the presence of stimulus-induced oscillatory patterns in the honeybee antennal lobe, and to analyse the distribution of those patterns across the antennal lobe glomeruli. Fast two-photon calcium imaging reveals the presence of low-frequency oscillations, the intensity of which is perturbed by an incoming stimulus. Moreover, analysis of the spatial arrangement of this activity indicates that it is not homogeneous throughout the antennal lobe. On the contrary, each glomerulus displays an odorant-specific time-frequency profile, and acts as a functional unit of the oscillatory activity. The presented approach allows simultaneous recording of complex activity patterns across several nodes of the antennal lobe, providing the means to better understand the network dynamics regulating olfactory coding and leading to perception.

关键词： honeybee sensory coding time-frequency analysis two-photon microscopy

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Hierarchical sparse coding in the sensory system of Caenorhabditis elegans

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PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA 2015年第4期112卷 1185-1189页

作者： Zaslaver, Alon Liani, Idan Shtangel, Oshrat Ginzburg, Shira Yee, Lisa Sternberg, Paul W. Hebrew Univ Jerusalem Alexander Silberman Inst Life Sci Dept Genet IL-91904 Jerusalem Israel CALTECH Howard Hughes Med Inst Pasadena CA 91125 USA CALTECH Div Biol Pasadena CA 91125 USA CALTECH Div Biol Engn Pasadena CA 91125 USA

Animals with compact sensory systems face an encoding problem where a small number of sensory neurons are required to encode information about its surrounding complex environment. Using Caenorhabditis elegans worms as a model, we ask how chemical stimuli are encoded by a small and highly connected sensory system. We first generated a comprehensive library of transgenic worms where each animal expresses a genetically encoded calcium indicator in individual sensory neurons. This library includes the vast majority of the sensory system in C. elegans. Imaging from individual sensory neurons while subjecting the worms to various stimuli allowed us to compile a comprehensive functional map of the sensory system at single neuron resolution. The functional map reveals that despite the dense wiring, chemosensory neurons represent the environment using sparse codes. Moreover, although anatomically closely connected, chemo-and mechano-sensory neurons are functionally segregated. In addition, the code is hierarchical, where few neurons participate in encoding multiple cues, whereas other sensory neurons are stimulus specific. This encoding strategy may have evolved to mitigate the constraints of a compact sensory system.

关键词： neural circuits calcium imagaing sensory coding

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A minimum-error, energy-constrained neural code is an instantaneous-rate code

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JOURNAL OF COMPUTATIONAL NEUROSCIENCE 2016年第2期40卷 193-206页

作者： Johnson, Erik C. Jones, Douglas L. Ratnam, Rama Univ Illinois Dept Elect & Comp Engn Urbana IL 61801 USA Univ Illinois Coordinated Sci Lab Urbana IL 61801 USA Univ Illinois Beckman Inst Adv Sci & Technol Urbana IL 61801 USA Singapore Pte Ltd Adv Digital Sci Ctr Singapore Singapore Univ Illinois Neurosci Program Urbana IL 61801 USA

sensory neurons code information about stimuli in their sequence of action potentials (spikes). Intuitively, the spikes should represent stimuli with high fidelity. However, generating and propagating spikes is a metabolically expensive process. It is therefore likely that neural codes have been selected to balance energy expenditure against encoding error. Our recently proposed optimal, energy-constrained neural coder (Jones et al. Frontiers in Computational Neuroscience, 9, 61 2015) postulates that neurons time spikes to minimize the trade-off between stimulus reconstruction error and expended energy by adjusting the spike threshold using a simple dynamic threshold. Here, we show that this proposed coding scheme is related to existing coding schemes, such as rate and temporal codes. We derive an instantaneous rate coder and show that the spike-rate depends on the signal and its derivative. In the limit of high spike rates the spike train maximizes fidelity given an energy constraint (average spike-rate), and the predicted interspike intervals are identical to those generated by our existing optimal coding neuron. The instantaneous rate coder is shown to closely match the spike-rates recorded from P-type primary afferents in weakly electric fish. In particular, the coder is a predictor of the peristimulus time histogram (PSTH). When tested against in vitro cortical pyramidal neuron recordings, the instantaneous spike-rate approximates DC step inputs, matching both the average spike-rate and the time-to-first-spike (a simple temporal code). Overall, the instantaneous rate coder relates optimal, energy-constrained encoding to the concepts of rate-coding and temporal-coding, suggesting a possible unifying principle of neural encoding of sensory signals.

关键词： Rate coding Temporal coding Instantaneous rate sensory coding Energy efficient coding

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