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A quest for excitation: Theoretical arguments and immunohistochemical evidence of excitatory granular cells in the ELL of Gnathonemus petersii

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Journal of Physiology Paris 2016年第3期110卷 190-199页

作者： Hollmann, V. Engelmann, J. Gómez-Sena, L. University of Bielefeld Faculty of Biology AG Active Sensing Germany Sección Biomatemática Laboratorio de Neurociencias Facultad de Ciencias UdelaR Uruguay

The Electrosensory Lateral Line lobe (ELL) is the first central target where the electrosensory information encoded in the spatiotemporal pattern electroreceptor afferent discharges is processed. These afferents encode the minute amplitude changes of the basal electric field through both a change in latency and discharge rate. In the ELL the time and rate-coded input pattern of the sensory periphery goes through the granular cell layer before reaching the main efferent cells of the network: large fusiform (LF) and large ganglion (LG) cells. The evidence until now shows that granular cells are inhibitory. Given that large fusiform cells are excited by the sensory input, it remains a mystery how the afferent input produce excitation through a layer composed by only inhibitory cells. We addressed this problem by modeling how the known circuitry of the ELL could produce excitation in LF cells with only inhibitory granular cells. Alternatively we show that a network composed of a mix of excitatory and inhibitory granular cell not only performs better, as expected, carrying excitation to LF cells but it does so robustly and at higher sensitivity by enhancing the contrast of the electric image between the periphery and the ELLs output. We then show with refined histological methods that a subpopulation of the granular cells indeed are excitatory, providing the necessary input for this contrast enhancing mechanism. © 2016 Elsevier Ltd

关键词： Electric fish Immunohistochemistry Integrate and fire modeling Networks sensory coding

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Maturation of suprathreshold auditory nerve activity involves cochlear CGRP-receptor complex formation

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PHYSIOLOGICAL REPORTS 2016年第14期4卷 12869-12869页

作者： Dickerson, Ian M. Bussey-Gaborski, Rhiannon Holt, Joseph C. Jordan, Paivi M. Luebke, Anne E. Univ Rochester Med Ctr Deptartment Neurosci Rochester NY 14642 USA Univ Rochester Med Ctr Deptartment Biomed Engn Rochester NY 14642 USA Univ Rochester Med Ctr Deptartment Otolaryngol Rochester NY 14642 USA

In adult animals, the neuropeptide calcitonin gene-related peptide (CGRP) is contained in cochlear efferent fibers projecting out to the cochlea, and contributes to increased suprathreshold sound-evoked activity in the adult auditory nerve. Similarly, CGRP applied to the lateral-line organ (hair cell organ) increases afferent nerve activity in adult frogs (post-metamorphic day 30), yet this increase is developmentally delayed from post-metamorphic day 4-30. In this study, we discovered that there was also a developmental delay in increased suprathreshold sound-evoked activity auditory nerve between juvenile and adult mice similar to what had been observed previously in frog. Moreover, juvenile mice with a targeted deletion of the CGRP gene [CGRP null (-/-)] did not show a similar developmental increase in nerve activity, suggesting CGRP signaling is involved. This developmental delay is not due to a delay in CGRP expression, but instead is due to a delay in receptor formation. We observed that the increase in sound-evoked nerve activity is correlated with increased formation of cochlear CGRP receptors, which require three complexed proteins (CLR, RAMP1, RCP) to be functional. CGRP receptor formation in the cochlea was incomplete at 1month of age (juvenile), but complete by 3months (adult), which corresponded to the onset of suprathreshold enhancement of sound-evoked activity in wild-type animals. Taken together, these data support a model for cochlear function that is enhanced by maturation of CGRP receptor complexes.

关键词： CGRP CGRP-RCP CLR cochlea cochlear nerve co-immunoprecipitation developmental efferent juvenile lateral olivocochlear efferents mouse RAMP1 sensory coding

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coding principles of the canonical cortical microcircuit in the avian brain

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PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA 2015年第11期112卷 3517-3522页

作者： Calabrese, Ana Woolley, Sarah M. N. Columbia Univ Program Neurobiol & Behav New York NY 10027 USA Columbia Univ Dept Psychol New York NY 10027 USA Columbia Univ Kavli Inst New York NY 10027 USA

Mammalian neocortex is characterized by a layered architecture and a common or "canonical" microcircuit governing information flow among layers. This microcircuit is thought to underlie the computations required for complex behavior. Despite the absence of a six-layered cortex, birds are capable of complex cognition and behavior. In addition, the avian auditory pallium is composed of adjacent information-processing regions with genetically identified neuron types and projections among regions comparable with those found in the neocortex. Here, we show that the avian auditory pallium exhibits the same information-processing principles that define the canonical cortical microcircuit, long thought to have evolved only in mammals. These results suggest that the canonical cortical microcircuit evolved in a common ancestor of mammals and birds and provide a physiological explanation for the evolution of neural processes that give rise to complex behavior in the absence of cortical lamination.

关键词： functional connectivity cortex evolution songbird sensory coding

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Fast and robust estimation of spectro-temporal receptive fields using stochastic approximations

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JOURNAL OF NEUROSCIENCE METHODS 2015年第0期246卷 119-133页

作者： Meyer, Arne F. Diepenbrock, Jan-Philipp Ohl, Frank W. Anermueller, Joern Carl von Ossietzky Univ Oldenburg Med Phys & Cluster Excellence Hearing4all D-26111 Oldenburg Germany Leibniz Inst Neurobiol D-39118 Magdeburg Germany Otto Von Guericke Univ Inst Biol D-39118 Magdeburg Germany

Background: The receptive field (RF) represents the signal preferences of sensory neurons and is the primary analysis method for understanding sensory coding. While it is essential to estimate a neuron's RF, finding numerical solutions to increasingly complex RF models can become computationally intensive, in particular for high-dimensional stimuli or when many neurons are involved. New method: Here we propose an optimization scheme based on stochastic approximations that facilitate this task. The basic idea is to derive solutions on a random subset rather than computing the full solution on the available data set. To test this, we applied different optimization schemes based on stochastic gradient descent (SGD) to both the generalized linear model (GLM) and a recently developed classification-based RF estimation approach. Results and comparison with existing method: Using simulated and recorded responses, we demonstrate that RF parameter optimization based on state-of-the-art SGD algorithms produces robust estimates of the spectra-temporal receptive field (STRF). Results on recordings from the auditory midbrain demonstrate that stochastic approximations preserve both predictive power and tuning properties of STRFs. A correlation of 0.93 with the STRF derived from the full solution may be obtained in less than 10% of the full solution's estimation time. We also present an on-line algorithm that allows simultaneous monitoring of STRF properties of more than 30 neurons on a single computer. Conclusions: The proposed approach may not only prove helpful for large-scale recordings but also provides a more comprehensive characterization of neural tuning in experiments than standard tuning curves. (C) 2015 Elsevier B.V. All rights reserved.

关键词： sensory coding Receptive field Auditory system Generalized linear model Stochastic gradient descent On-line learning

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Effects of changing skin mechanics on the differential sensitivity to surface compliance by tactile afferents in the human finger pad

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JOURNAL OF NEUROPHYSIOLOGY 2015年第4期114卷 2249-2257页

作者： Hudson, Kathryn M. Condon, Melia Ackerley, Rochelle McGlone, Francis Olausson, Hakan Macefield, Vaughan G. Birznieks, Ingvars Univ Western Sydney Sch Med Sydney NSW Australia Univ Western Sydney Sch Sci & Hlth Sydney NSW Australia Univ Gothenburg Dept Clin Neurophysiol Gothenburg Sweden Liverpool John Moores Univ Liverpool L3 5UX Merseyside England Neurosci Res Australia Sydney NSW Australia Univ Western Sydney MARCS Inst Sydney NSW Australia

It is not known how changes in skin mechanics affect the responses of cutaneous mechanoreceptors in the finger pads to compression forces. We used venous occlusion to change the stiffness of the fingers and investigated whether this influenced the firing of low-threshold mechanoreceptors to surfaces of differing stiffness. Unitary recordings were made from 10 slowly adapting type I (SAI), 10 fast adapting type I (FAI) and 9 slowly adapting type II (SAII) units via tungsten microelectrodes inserted into the median nerve at the wrist. A servo-controlled stimulator applied ramp-and-hold forces (1, 2, and 4 N) at a constant loading and unloading rate (2 N/s) via a flat 2.5-cm-diameter silicone disk over the center of the finger pad. Nine silicone disks (objects), varying in compliance, were used. Venous occlusion, produced by inflating a sphygmomanometer cuff around the upper arm to 40 +/- 5 mmHg, was used to induce swelling of the fingers and increase the compliance of the finger pulp. Venous occlusion had no effect on the firing rates of the SAI afferents, nor on the slopes of the relationship between mean firing rate and object compliance at each amplitude, but did significantly reduce the slopes for the FAI afferents. Although the SAII afferents possess a poor capacity to encode changes in object compliance, mean firing rates were significantly lower during venous occlusion. The finding that venous occlusion had no effect on the firing properties of SAI afferents indicates that these afferents preserve their capacity to encode changes in object compliance, despite changes in skin mechanics.

关键词： tactile afferents human microneurography sensory coding skin mechanics

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Olfactory coding in the insect brain: data and conjectures

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EUROPEAN JOURNAL OF NEUROSCIENCE 2014年第11期39卷 1784-1795页

作者： Galizia, C. Giovanni Univ Konstanz D-78457 Constance Germany

Much progress has been made recently in understanding how olfactory coding works in insect brains. Here, I propose a wiring diagram for the major steps from the first processing network (the antennal lobe) to behavioral readout. I argue that the sequence of lateral inhibition in the antennal lobe, non-linear synapses, threshold-regulating gated spring network, selective lateral inhibitory networks across glomeruli, and feedforward inhibition to the lateral protocerebrum cover most of the experimental results from different research groups and model species. I propose that the main difference between mushroom bodies and the lateral protocerebrum is not about learned vs. innate behavior. Rather, mushroom bodies perform odor identification, whereas the lateral protocerebrum performs odor evaluation (both learned and innate). I discuss the concepts of labeled line and combinatorial coding and postulate that, under restrictive experimental conditions, these networks lead to an apparent existence of labeled line' coding for special odors. Modulatory networks are proposed as switches between different evaluating systems in the lateral protocerebrum. A review of experimental data and theoretical conjectures both contribute to this synthesis, creating new hypotheses for future research.

关键词： antennal lobe mushroom bodies neural networks sensory coding

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Early vestibular processing does not discriminate active from passive self-motion if there is a discrepancy between predicted and actual proprioceptive feedback

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JOURNAL OF NEUROPHYSIOLOGY 2014年第12期111卷 2465-2478页

作者： Brooks, Jessica X. Cullen, Kathleen E. McGill Univ Dept Physiol Aerosp Med Res Unit Montreal PQ H3G 1Y6 Canada

Most of our sensory experiences are gained by active exploration of the world. While the ability to distinguish sensory inputs resulting of our own actions (termed reafference) from those produced externally (termed exafference) is well established, the neural mechanisms underlying this distinction are not fully understood. We have previously proposed that vestibular signals arising from self-generated movements are inhibited by a mechanism that compares the internal prediction of the proprioceptive consequences of self-motion to the actual feedback. Here we directly tested this proposal by recording from single neurons in monkey during vestibular stimulation that was externally produced and/or self-generated. We show for the first time that vestibular reafference is equivalently canceled for self-generated sensory stimulation produced by activation of the neck musculature (head-on-body motion), or axial musculature (combined head and body motion), when there is no discrepancy between the predicted and actual proprioceptive consequences of self-motion. However, if a discrepancy does exist, central vestibular neurons no longer preferentially encode vestibular exafference. Specifically, when simultaneous active and passive motion resulted in activation of the same muscle proprioceptors, neurons robustly encoded the total vestibular input (i.e., responses to vestibular reafference and exafference were equally strong), rather than exafference alone. Taken together, our results show that the cancellation of vestibular reafference in early vestibular processing requires an explicit match between expected and actual proprioceptive feedback. We propose that this vital neuronal computation, necessary for both accurate sensory perception and motor control, has important implications for a variety of sensory systems that suppress self-generated signals.

关键词： sensory coding self-motion response selectivity efference copy voluntary movement vestibular proprioception

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Encoding of social signals in all three electrosensory pathways of Eigenmannia virescens

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JOURNAL OF NEUROPHYSIOLOGY 2014年第9期112卷 2076-2091页

作者： Stoeckl, Anna Sinz, Fabian Benda, Jan Grewe, Jan Univ Munich Dept Biol 2 Munich Germany Lund Univ Dept Biol Lund Sweden Univ Tubingen Inst Neurobiol Tubingen Germany Bernstein Ctr Computat Neurosci Tubingen Germany

Extracting complementary features in parallel pathways is a widely used strategy for a robust representation of sensory signals. Weakly electric fish offer the rare opportunity to study complementary encoding of social signals in all of its electrosensory pathways. Electrosensory information is conveyed in three parallel pathways: two receptor types of the tuberous (active) system and one receptor type of the ampullary (passive) system. Modulations of the fish's own electric field are sensed by these receptors and used in navigation, prey detection, and communication. We studied the neuronal representation of electric communication signals (called chirps) in the ampullary and the two tuberous pathways of Eigenmannia virescens. We first characterized different kinds of chirps observed in behavioral experiments. Since Eigenmannia chirps simultaneously drive all three types of receptors, we studied their responses in in vivo electrophysiological recordings. Our results demonstrate that different electroreceptor types encode different aspects of the stimuli and each appears best suited to convey information about a certain chirp type. A decoding analysis of single neurons and small populations shows that this specialization leads to a complementary representation of information in the tuberous and ampullary receptors. This suggests that a potential readout mechanism should combine information provided by the parallel processing streams to improve chirp detectability.

关键词： communication decoding parallel processing sensory coding weakly electric fish

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Static frequency tuning accounts for changes in neural synchrony evoked by transient communication signals

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JOURNAL OF NEUROPHYSIOLOGY 2014年第4期112卷 752-765页

作者： Walz, Henriette Grewe, Jan Benda, Jan Bernstein Ctr Computat Neurosci Munich Planegg Martinsried Germany Univ Tubingen Inst Neurobiol D-72076 Tubingen Germany

Although communication signals often vary continuously on the underlying signal parameter, they are perceived as distinct categories. We here report the opposite case where an electrocommunication signal is encoded in four distinct regimes, although the behavior described to date does not show distinct categories. In particular, we studied the encoding of chirps by P-unit afferents in the weakly electric fish Apteronotus leptorhynchus. These fish generate an electric organ discharge that oscillates at a certain individual-specific frequency. The interaction of two fish in communication contexts leads to the emergence of a beating amplitude modulation (AM) at the frequency difference between the two individual signals. This frequency difference represents the social context of the encounter. Chirps are transient increases of the fish's frequency leading to transient changes in the frequency of the AM. We stimulated the cells with the same chirp on different, naturally occurring backgrounds beats. The P-units responded either by synchronization or desynchronization depending on the background. Although the duration of a chirp is often shorter than a full cycle of the AM it elicits, the distinct responses of the P-units to the chirp can be predicted solely from the frequency of the AM based on the static frequency tuning of the cells.

关键词： communication signals sensory coding spike synchrony weakly electric fish

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Temporal variability of spectro-temporal receptive fields in the anesthetized auditory cortex

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FRONTIERS IN COMPUTATIONAL NEUROSCIENCE 2014年第DEC期8卷 1-16页

作者： Meyer, Arne F. Diepenbrock, Jan-Philipp Ohl, Frank W. Anemueller, Joern Carl von Ossietzky Univ Oldenburg Dept Med Phys & Accoust D-26129 Oldenburg Germany Carl von Ossietzky Univ Oldenburg Dept Med Phys & Accoust Cluster Excellence Hearing4all D-26129 Oldenburg Germany Leibniz Inst Neurobiol Dept Syst Physiol Learning Magdeburg Germany Otto Von Guericke Univ Inst Biol Dept Med Phys & Accoust Magdeburg Germany

Temporal variability of neuronal response characteristics during sensory stimulation is a ubiquitous phenomenon that may reflect processes such as stimulus-driven adaptation, top-down modulation or spontaneous fluctuations. It poses a challenge to functional characterization methods such as the receptive field, since these often assume stationarity. We propose a novel method for estimation of sensory neurons' receptive fields that extends the classic static linear receptive field model to the time-varying case. Here, the long-term estimate of the static receptive field serves as the mean of a probabilistic prior distribution from which the short-term temporally localized receptive field may deviate stochastically with time-varying standard deviation. The derived corresponding generalized linear model permits robust characterization of temporal variability in receptive field structure also for highly non-Gaussian stimulus ensembles. We computed and analyzed short-term auditory spectro-temporal receptive field (SIRE) estimates with characteristic temporal resolution 5-30 s based on model simulations and responses from in total 60 single-unit recordings in anesthetized Mongolian gerbil auditory midbrain and cortex. Stimulation was performed with short (100 ms) overlapping frequency-modulated tones. Results demonstrate identification of time-varying STRFs, with obtained predictive model likelihoods exceeding those from baseline static SIRE estimation. Quantitative characterization of SIRE variability reveals a higher degree thereof in auditory cortex compared to midbrain. Cluster analysis indicates that significant deviations from the long-term static SIRE are brief, but reliably estimated. We hypothesize that the observed variability more likely reflects spontaneous or state-dependent internal fluctuations that interact with stimulus-induced processing, rather than experimental or stimulus design.

关键词： sensory coding receptive field inferior colliculus auditory cortex time-varying zero-mean prior generalized linear model

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