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Severson KS, Xu D, Van de Loo M, Bai L, Ginty DD, O'Connor DH. Active Touch and Self-Motion Encoding by Merkel Cell-Associated Afferents. Neuron 2017; 94:666-676.e9. [PMID: 28434802 DOI: 10.1016/j.neuron.2017.03.045] [Citation(s) in RCA: 66] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2016] [Revised: 02/15/2017] [Accepted: 03/29/2017] [Indexed: 01/12/2023]
Abstract
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.
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Affiliation(s)
- Kyle S Severson
- Kavli Neuroscience Discovery Institute, Brain Science Institute, The Solomon H. Snyder Department of Neuroscience, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA; Neuroscience Training Program, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Duo Xu
- Kavli Neuroscience Discovery Institute, Brain Science Institute, The Solomon H. Snyder Department of Neuroscience, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA; Neuroscience Training Program, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Margaret Van de Loo
- Kavli Neuroscience Discovery Institute, Brain Science Institute, The Solomon H. Snyder Department of Neuroscience, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Ling Bai
- Department of Neurobiology, Howard Hughes Medical Institute, Harvard Medical School, 220 Longwood Avenue, Boston, MA 02115, USA; Neuroscience Training Program, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - David D Ginty
- Department of Neurobiology, Howard Hughes Medical Institute, Harvard Medical School, 220 Longwood Avenue, Boston, MA 02115, USA
| | - Daniel H O'Connor
- Kavli Neuroscience Discovery Institute, Brain Science Institute, The Solomon H. Snyder Department of Neuroscience, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
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52
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Claverie LN, Boubenec Y, Debrégeas G, Prevost AM, Wandersman E. Whisker Contact Detection of Rodents Based on Slow and Fast Mechanical Inputs. Front Behav Neurosci 2017; 10:251. [PMID: 28119582 PMCID: PMC5222834 DOI: 10.3389/fnbeh.2016.00251] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2016] [Accepted: 12/23/2016] [Indexed: 11/13/2022] Open
Abstract
Rodents use their whiskers to locate nearby objects with an extreme precision. To perform such tasks, they need to detect whisker/object contacts with a high temporal accuracy. This contact detection is conveyed by classes of mechanoreceptors whose neural activity is sensitive to either slow or fast time varying mechanical stresses acting at the base of the whiskers. We developed a biomimetic approach to separate and characterize slow quasi-static and fast vibrational stress signals acting on a whisker base in realistic exploratory phases, using experiments on both real and artificial whiskers. Both slow and fast mechanical inputs are successfully captured using a mechanical model of the whisker. We present and discuss consequences of the whisking process in purely mechanical terms and hypothesize that free whisking in air sets a mechanical threshold for contact detection. The time resolution and robustness of the contact detection strategies based on either slow or fast stress signals are determined. Contact detection based on the vibrational signal is faster and more robust to exploratory conditions than the slow quasi-static component, although both slow/fast components allow localizing the object.
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Affiliation(s)
- Laure N Claverie
- Sorbonne Universités, UPMC Univ Paris 06, UMR 8237, Laboratoire Jean Perrin Paris, France
| | - Yves Boubenec
- Laboratoire des Systèmes Perceptifs, Département d'études Cognitives, ENS, PSL Research University, Centre National de la Recherche Scientifique Paris, France
| | - Georges Debrégeas
- Sorbonne Universités, UPMC Univ Paris 06, UMR 8237, Laboratoire Jean Perrin Paris, France
| | - Alexis M Prevost
- Sorbonne Universités, UPMC Univ Paris 06, UMR 8237, Laboratoire Jean Perrin Paris, France
| | - Elie Wandersman
- Sorbonne Universités, UPMC Univ Paris 06, UMR 8237, Laboratoire Jean Perrin Paris, France
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53
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Belli HM, Yang AET, Bresee CS, Hartmann MJZ. Variations in vibrissal geometry across the rat mystacial pad: base diameter, medulla, and taper. J Neurophysiol 2016; 117:1807-1820. [PMID: 27881718 DOI: 10.1152/jn.00054.2016] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2016] [Accepted: 11/02/2016] [Indexed: 11/22/2022] Open
Abstract
Many rodents tactually sense the world through active motions of their vibrissae (whiskers), which are regularly arranged in rows and columns (arcs) on the face. The present study quantifies several geometric parameters of rat whiskers that determine the tactile information acquired. Findings include the following. 1) A meta-analysis of seven studies shows that whisker base diameter varies with arc length with a surprisingly strong dependence on the whisker's row position within the array. 2) The length of the whisker medulla varies linearly with whisker length, and the medulla's base diameter varies linearly with whisker base diameter. 3) Two parameters are required to characterize whisker "taper": radius ratio (base radius divided by tip radius) and radius slope (the difference between base and tip radius, divided by arc length). A meta-analysis of five studies shows that radius ratio exhibits large variability due to variations in tip radius, while radius slope varies systematically across the array. 4) Within the resolution of the present study, radius slope does not differ between the proximal and distal segments of the whisker, where "proximal" is defined by the presence of the medulla. 5) Radius slope of the medulla is offset by a constant value from radius slope of the proximal portion of the whisker. We conclude with equations for all geometric parameters as functions of row and column position.NEW & NOTEWORTHY Rats tactually explore their world by brushing and tapping their whiskers against objects. Each whisker's geometry will have a large influence on its mechanics and thus on the tactile signals the rat obtains. We performed a meta-analysis of seven studies to generate equations that describe systematic variations in whisker geometry across the rat's face. We also quantified the geometry of the whisker medulla. A database provides access to geometric parameters of over 500 rat whiskers.
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Affiliation(s)
- Hayley M Belli
- Department of Biomedical Engineering, Northwestern University, Evanston, Illinois
| | - Anne E T Yang
- Department of Mechanical Engineering, Northwestern University, Evanston, Illinois; and
| | - Chris S Bresee
- Interdepartmental Neuroscience Program, Northwestern University, Evanston, Illinois
| | - Mitra J Z Hartmann
- Department of Biomedical Engineering, Northwestern University, Evanston, Illinois; .,Department of Mechanical Engineering, Northwestern University, Evanston, Illinois; and
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54
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Layer 4 fast-spiking interneurons filter thalamocortical signals during active somatosensation. Nat Neurosci 2016; 19:1647-1657. [PMID: 27749825 DOI: 10.1038/nn.4412] [Citation(s) in RCA: 68] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2016] [Accepted: 09/08/2016] [Indexed: 01/03/2023]
Abstract
We rely on movement to explore the environment, for example, by palpating an object. In somatosensory cortex, activity related to movement of digits or whiskers is suppressed, which could facilitate detection of touch. Movement-related suppression is generally assumed to involve corollary discharges. Here we uncovered a thalamocortical mechanism in which cortical fast-spiking interneurons, driven by sensory input, suppress movement-related activity in layer 4 (L4) excitatory neurons. In mice locating objects with their whiskers, neurons in the ventral posteromedial nucleus (VPM) fired in response to touch and whisker movement. Cortical L4 fast-spiking interneurons inherited these responses from VPM. In contrast, L4 excitatory neurons responded mainly to touch. Optogenetic experiments revealed that fast-spiking interneurons reduced movement-related spiking in excitatory neurons, enhancing selectivity for touch-related information during active tactile sensation. These observations suggest a fundamental computation performed by the thalamocortical circuit to accentuate salient tactile information.
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55
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Whisking mechanics and active sensing. Curr Opin Neurobiol 2016; 40:178-188. [PMID: 27632212 DOI: 10.1016/j.conb.2016.08.001] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2016] [Revised: 08/03/2016] [Accepted: 08/04/2016] [Indexed: 11/20/2022]
Abstract
We describe recent advances in quantifying the three-dimensional (3D) geometry and mechanics of whisking. Careful delineation of relevant 3D reference frames reveals important geometric and mechanical distinctions between the localization problem ('where' is an object) and the feature extraction problem ('what' is an object). Head-centered and resting-whisker reference frames lend themselves to quantifying temporal and kinematic cues used for object localization. The whisking-centered reference frame lends itself to quantifying the contact mechanics likely associated with feature extraction. We offer the 'windowed sampling' hypothesis for active sensing: that rats can estimate an object's spatial features by integrating mechanical information across whiskers during brief (25-60ms) windows of 'haptic enclosure' with the whiskers, a motion that resembles a hand grasp.
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McGuire LM, Telian G, Laboy-Juárez KJ, Miyashita T, Lee DJ, Smith KA, Feldman DE. Short Time-Scale Sensory Coding in S1 during Discrimination of Whisker Vibrotactile Sequences. PLoS Biol 2016; 14:e1002549. [PMID: 27574970 PMCID: PMC5004814 DOI: 10.1371/journal.pbio.1002549] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2016] [Accepted: 08/09/2016] [Indexed: 11/18/2022] Open
Abstract
Rodent whisker input consists of dense microvibration sequences that are often temporally integrated for perceptual discrimination. Whether primary somatosensory cortex (S1) participates in temporal integration is unknown. We trained rats to discriminate whisker impulse sequences that varied in single-impulse kinematics (5–20-ms time scale) and mean speed (150-ms time scale). Rats appeared to use the integrated feature, mean speed, to guide discrimination in this task, consistent with similar prior studies. Despite this, 52% of S1 units, including 73% of units in L4 and L2/3, encoded sequences at fast time scales (≤20 ms, mostly 5–10 ms), accurately reflecting single impulse kinematics. 17% of units, mostly in L5, showed weaker impulse responses and a slow firing rate increase during sequences. However, these units did not effectively integrate whisker impulses, but instead combined weak impulse responses with a distinct, slow signal correlated to behavioral choice. A neural decoder could identify sequences from fast unit spike trains and behavioral choice from slow units. Thus, S1 encoded fast time scale whisker input without substantial temporal integration across whisker impulses. Recordings in whisker somatosensory cortex of rats during discrimination of rapid whisker deflection sequences show that whisker input is encoded at very short time scales (less than 20 ms). Sensory input is rich in temporal patterns, but how the brain processes this temporal information is not well understood. This process is important in the whisker tactile system of rodents, in which active whisking on objects generates dense streams of stick-slip and contact events. Rats can discriminate vibrotactile sequences applied to the whiskers, and prior studies show that this often involves behavioral integration over time to calculate mean whisker-speed. How the brain represents and integrates vibrotactile input is not known. We recorded neural activity in primary somatosensory cortex as rats discriminated rapid vibrotactile sequences. We found that neurons in the primary somatosensory cortex encoded whisker sensory information at very fast time scales (<20 ms), without evidence for substantial temporal integration. A subset of neurons encoded relatively little stimulus information but strongly encoded the rat’s behavioral choice on each trial. Thus, primary sensory cortex represents immediate sensory input, suggesting that temporal integration occurs in downstream brain areas.
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Affiliation(s)
- Leah M. McGuire
- Department of Molecular and Cellular Biology, and Helen Wills Neuroscience Institute, University of California Berkeley, Berkeley, California, United States of America
| | - Gregory Telian
- Department of Molecular and Cellular Biology, and Helen Wills Neuroscience Institute, University of California Berkeley, Berkeley, California, United States of America
| | - Keven J. Laboy-Juárez
- Department of Molecular and Cellular Biology, and Helen Wills Neuroscience Institute, University of California Berkeley, Berkeley, California, United States of America
| | - Toshio Miyashita
- Department of Molecular and Cellular Biology, and Helen Wills Neuroscience Institute, University of California Berkeley, Berkeley, California, United States of America
| | - Daniel J. Lee
- Department of Molecular and Cellular Biology, and Helen Wills Neuroscience Institute, University of California Berkeley, Berkeley, California, United States of America
| | - Katherine A. Smith
- Department of Molecular and Cellular Biology, and Helen Wills Neuroscience Institute, University of California Berkeley, Berkeley, California, United States of America
| | - Daniel E. Feldman
- Department of Molecular and Cellular Biology, and Helen Wills Neuroscience Institute, University of California Berkeley, Berkeley, California, United States of America
- * E-mail:
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57
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Yang AET, Hartmann MJZ. Whisking Kinematics Enables Object Localization in Head-Centered Coordinates Based on Tactile Information from a Single Vibrissa. Front Behav Neurosci 2016; 10:145. [PMID: 27486390 PMCID: PMC4949211 DOI: 10.3389/fnbeh.2016.00145] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2016] [Accepted: 06/23/2016] [Indexed: 11/13/2022] Open
Abstract
During active tactile exploration with their whiskers (vibrissae), rodents can rapidly orient to an object even though there are very few proprioceptors in the whisker muscles. Thus a long-standing question in the study of the vibrissal system is how the rat can localize an object in head-centered coordinates without muscle-based proprioception. We used a three-dimensional model of whisker bending to simulate whisking motions against a peg to investigate the possibility that the 3D mechanics of contact from a single whisker are sufficient for localization in head-centered coordinates. Results show that for nearly all whiskers in the array, purely tactile signals at the whisker base - as would be measured by mechanoreceptors, in whisker-centered coordinates - could be used to determine the location of a vertical peg in head-centered coordinates. Both the "roll" and the "elevation" components of whisking kinematics contribute to the uniqueness and resolution of the localization. These results offer an explanation for a behavioral study showing that rats can more accurately determine the horizontal angle of an object if one column, rather than one row, of whiskers is spared.
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Affiliation(s)
- Anne E T Yang
- Department of Mechanical Engineering, Northwestern University, Evanston IL, USA
| | - Mitra J Z Hartmann
- Department of Mechanical Engineering, Northwestern University, EvanstonIL, USA; Department of Biomedical Engineering, Northwestern University, EvanstonIL, USA
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58
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Bush NE, Schroeder CL, Hobbs JA, Yang AE, Huet LA, Solla SA, Hartmann MJ. Decoupling kinematics and mechanics reveals coding properties of trigeminal ganglion neurons in the rat vibrissal system. eLife 2016; 5. [PMID: 27348221 PMCID: PMC4999311 DOI: 10.7554/elife.13969] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2015] [Accepted: 06/26/2016] [Indexed: 11/13/2022] Open
Abstract
Tactile information available to the rat vibrissal system begins as external forces that cause whisker deformations, which in turn excite mechanoreceptors in the follicle. Despite the fundamental mechanical origin of tactile information, primary sensory neurons in the trigeminal ganglion (Vg) have often been described as encoding the kinematics (geometry) of object contact. Here we aimed to determine the extent to which Vg neurons encode the kinematics vs. mechanics of contact. We used models of whisker bending to quantify mechanical signals (forces and moments) at the whisker base while simultaneously monitoring whisker kinematics and recording single Vg units in both anesthetized rats and awake, body restrained rats. We employed a novel manual stimulation technique to deflect whiskers in a way that decouples kinematics from mechanics, and used Generalized Linear Models (GLMs) to show that Vg neurons more directly encode mechanical signals when the whisker is deflected in this decoupled stimulus space. DOI:http://dx.doi.org/10.7554/eLife.13969.001 Animals must gather sensory information from the world around them and act on that information. Specialized sensory cells convert physical information from the environment into electrical signals that the brain can interpret. In the case of hearing, this physical information consists of changes in air pressure, and for vision, it is patterns of light bouncing off of objects. Rodents rely heavily on touch information from their whiskers to explore their world. When a whisker touches an object, it deforms and bends. The first neurons to respond to whisker touch – so called primary sensory neurons – represent contact between the whisker and the object in the form of electrical signals, but exactly how they do this is unclear. One possibility is that primary sensory neurons encode the movement of the whisker itself. Whenever a whisker touches an object, the whisker is deflected in a particular direction by a particular amount and at a particular speed. These movement-related features are referred to as the “kinematic” properties of whisker-object contact. Alternatively, these whisker sensory neurons might be more concerned with the forces at the base of the whisker caused by object contact. These forces are the “mechanical” properties of whisker-object contact. Bush, Schroeder et al. set out to determine whether the electrical response of these whisker sensory neurons mainly encode kinematic or mechanical information. However, these two types of information are often closely related to each other: put simply, small whisker movements tend to accompany small forces and vice versa. Bush, Schroeder et al. therefore devised a method to deliver touch stimuli to the whiskers in a way that separates kinematic from mechanical information. Mathematical models were then developed to compare how well the neurons represent each type of information. The models showed that whisker sensory neurons generally encode mechanical signals more directly than kinematic ones. This information adds to our understanding of how animals learn about the world through their senses. However, the analysis of Bush, Schroeder et al. relies on the long-standing simplification that whisker motion is two-dimensional, whereas in reality whiskers move in three dimensions. Therefore, a future challenge is to examine how sensory neurons represent information about touch, such as the location or shape of an object, during three-dimensional whisker-object contact. DOI:http://dx.doi.org/10.7554/eLife.13969.002
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Affiliation(s)
- Nicholas E Bush
- Interdepartmental Neuroscience Program, Northwestern University, Evanston, United States
| | | | - Jennifer A Hobbs
- Department of Physics and Astronomy, Northwestern University, Evanston, United States
| | - Anne Et Yang
- Department of Mechanical Engineering, Northwestern University, Evanston, United States
| | - Lucie A Huet
- Department of Mechanical Engineering, Northwestern University, Evanston, United States
| | - Sara A Solla
- Department of Physics and Astronomy, Northwestern University, Evanston, United States.,Department of Physiology, Northwestern University, Chicago, United States
| | - Mitra Jz Hartmann
- Department of Biomedical Engineering, Northwestern University, Evanston, United States.,Department of Mechanical Engineering, Northwestern University, Evanston, United States
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59
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Hires SA, Schuyler A, Sy J, Huang V, Wyche I, Wang X, Golomb D. Beyond cones: an improved model of whisker bending based on measured mechanics and tapering. J Neurophysiol 2016; 116:812-24. [PMID: 27250911 DOI: 10.1152/jn.00511.2015] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2015] [Accepted: 05/22/2016] [Indexed: 11/22/2022] Open
Abstract
The sense of touch is represented by neural activity patterns evoked by mechanosensory input forces. The rodent whisker system is exceptional for studying the neurophysiology of touch in part because these forces can be precisely computed from video of whisker deformation. We evaluate the accuracy of a standard model of whisker bending, which assumes quasi-static dynamics and a linearly tapered conical profile, using controlled whisker deflections. We find significant discrepancies between model and experiment: real whiskers bend more than predicted upon contact at locations in the middle of the whisker and less at distal locations. Thus whiskers behave as if their stiffness near the base and near the tip is larger than expected for a homogeneous cone. We assess whether contact direction, friction, inhomogeneous elasticity, whisker orientation, or nonconical shape could explain these deviations. We show that a thin-middle taper of mouse whisker shape accounts for the majority of this behavior. This taper is conserved across rows and columns of the whisker array. The taper has a large effect on the touch-evoked forces and the ease with which whiskers slip past objects, which are key drivers of neural activity in tactile object localization and identification. This holds for orientations with intrinsic whisker curvature pointed toward, away from, or down from objects, validating two-dimensional models of simple whisker-object interactions. The precision of computational models relating sensory input forces to neural activity patterns can be quantitatively enhanced by taking thin-middle taper into account with a simple corrective function that we provide.
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Affiliation(s)
- Samuel Andrew Hires
- Neurobiology Section, Department of Biological Sciences, University of Southern California, Los Angeles, California;
| | - Adam Schuyler
- Neurobiology Section, Department of Biological Sciences, University of Southern California, Los Angeles, California
| | - Jonathan Sy
- Neurobiology Section, Department of Biological Sciences, University of Southern California, Los Angeles, California
| | - Vincent Huang
- Neurobiology Section, Department of Biological Sciences, University of Southern California, Los Angeles, California
| | - Isis Wyche
- Neurobiology Section, Department of Biological Sciences, University of Southern California, Los Angeles, California
| | - Xiyue Wang
- Neurobiology Section, Department of Biological Sciences, University of Southern California, Los Angeles, California
| | - David Golomb
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, Virginia; and Department of Physiology and Cell Biology, Department of Physics, and Zlotowski Center for Neuroscience, Faculty of Health Sciences, Ben Gurion University, Be'er-Sheva, Israel
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60
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Lucianna FA, Albarracín AL, Vrech SM, Farfán FD, Felice CJ. The mathematical whisker: A review of numerical models of the rat׳s vibrissa biomechanics. J Biomech 2016; 49:2007-2014. [PMID: 27260019 DOI: 10.1016/j.jbiomech.2016.05.019] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2016] [Revised: 04/27/2016] [Accepted: 05/15/2016] [Indexed: 11/25/2022]
Abstract
The vibrissal system of the rat refers to specialized hairs the animal uses for tactile sensory perception. Rats actively move their whiskers in a characteristic way called "whisking". Interaction with the environment produces elastic deformation of the whiskers, generating mechanical signals in the whisker-follicle complex. Advances in our understanding of the vibrissal complex biomechanics is of interest not only for the biological research field, but also for biomimetic approaches. The recent development of whisker numerical models has contributed to comprehending its sophisticated movements and its interactions with the follicle. The great diversity of behavioral patterns and complexities of the whisker-follicle ensemble encouraged the creation of many different biomechanical models. This review analyzes most of the whisker biomechanical models that have been developed so far. This review was written so as to render it accessible to readers coming from different research areas.
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Affiliation(s)
- Facundo Adrián Lucianna
- Laboratorio de Medios e Interfases (LAMEIN), Instituto Superior de Investigaciones Biológicas (INSIBIO), Universidad Nacional de Tucumán (UNT), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), San Miguel de Tucumán, Argentina.
| | - Ana Lía Albarracín
- Laboratorio de Medios e Interfases (LAMEIN), Instituto Superior de Investigaciones Biológicas (INSIBIO), Universidad Nacional de Tucumán (UNT), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), San Miguel de Tucumán, Argentina
| | - Sonia Mariel Vrech
- Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Center for Numerical and Computational Methods in Engineering (CEMCI), Universidad Nacional de Tucumán (UNT), San Miguel de Tucumán, Argentina
| | - Fernando Daniel Farfán
- Laboratorio de Medios e Interfases (LAMEIN), Instituto Superior de Investigaciones Biológicas (INSIBIO), Universidad Nacional de Tucumán (UNT), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), San Miguel de Tucumán, Argentina
| | - Carmelo José Felice
- Laboratorio de Medios e Interfases (LAMEIN), Instituto Superior de Investigaciones Biológicas (INSIBIO), Universidad Nacional de Tucumán (UNT), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), San Miguel de Tucumán, Argentina
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61
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Abstract
Perception of external objects involves sensory acquisition via the relevant sensory organs. A widely-accepted assumption is that the sensory organ is the first station in a serial chain of processing circuits leading to an internal circuit in which a percept emerges. This open-loop scheme, in which the interaction between the sensory organ and the environment is not affected by its concurrent downstream neuronal processing, is strongly challenged by behavioral and anatomical data. We present here a hypothesis in which the perception of external objects is a closed-loop dynamical process encompassing loops that integrate the organism and its environment and converging towards organism-environment steady-states. We discuss the consistency of closed-loop perception (CLP) with empirical data and show that it can be synthesized in a robotic setup. Testable predictions are proposed for empirical distinction between open and closed loop schemes of perception.
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Affiliation(s)
- Ehud Ahissar
- Department of Neurobiology, Weizmann Institute of Science, Rehovot, Israel
| | - Eldad Assa
- Department of Neurobiology, Weizmann Institute of Science, Rehovot, Israel
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62
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Huet LA, Hartmann MJZ. Simulations of a Vibrissa Slipping along a Straight Edge and an Analysis of Frictional Effects during Whisking. IEEE TRANSACTIONS ON HAPTICS 2016; 9:158-169. [PMID: 26829805 PMCID: PMC5753595 DOI: 10.1109/toh.2016.2522432] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
During tactile exploration, rats sweep their whiskers against objects in a motion called whisking. Here, we investigate how a whisker slips along an object's edge and how friction affects the resulting tactile signals. First, a frictionless model is developed to simulate whisker slip along a straight edge and compared with a previous model that incorporates friction but cannot simulate slip. Results of both models are compared to behavioral data obtained as a rat whisked against a smooth, stainless steel peg. As expected, the frictionless model predicts larger magnitudes of vertical slip than observed experimentally. The frictionless model also predicts forces and moments at the whisker base that are smaller and have a different direction than those predicted by the model with friction. Estimates for the friction coefficient yielded values near 0.48 (whisker/stainless steel). The present work provides the first assessments of the effects of friction on the mechanical signals received by the follicle during active whisking. It also demonstrates a proof-of-principle approach for reducing whisker tracking requirements during experiments and demonstrates the feasibility of simulating a full array of vibrissae whisking against a peg.
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63
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Campagner D, Evans MH, Bale MR, Erskine A, Petersen RS. Prediction of primary somatosensory neuron activity during active tactile exploration. eLife 2016; 5. [PMID: 26880559 PMCID: PMC4764568 DOI: 10.7554/elife.10696] [Citation(s) in RCA: 59] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2015] [Accepted: 01/06/2016] [Indexed: 11/13/2022] Open
Abstract
Primary sensory neurons form the interface between world and brain. Their function is well-understood during passive stimulation but, under natural behaving conditions, sense organs are under active, motor control. In an attempt to predict primary neuron firing under natural conditions of sensorimotor integration, we recorded from primary mechanosensory neurons of awake, head-fixed mice as they explored a pole with their whiskers, and simultaneously measured both whisker motion and forces with high-speed videography. Using Generalised Linear Models, we found that primary neuron responses were poorly predicted by whisker angle, but well-predicted by rotational forces acting on the whisker: both during touch and free-air whisker motion. These results are in apparent contrast to previous studies of passive stimulation, but could be reconciled by differences in the kinematics-force relationship between active and passive conditions. Thus, simple statistical models can predict rich neural activity elicited by natural, exploratory behaviour involving active movement of sense organs.
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Affiliation(s)
- Dario Campagner
- Faculty of Life Sciences, The University of Manchester, Manchester, United Kingdom
| | - Mathew Hywel Evans
- Faculty of Life Sciences, The University of Manchester, Manchester, United Kingdom
| | - Michael Ross Bale
- Faculty of Life Sciences, The University of Manchester, Manchester, United Kingdom.,School of Life Sciences, University of Sussex, Brighton, United Kingdom
| | - Andrew Erskine
- Faculty of Life Sciences, The University of Manchester, Manchester, United Kingdom.,Mill Hill Laboratory, The Francis Crick Institute, London, United Kingdom
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Schroeder JB, Ritt JT. Selection of head and whisker coordination strategies during goal-oriented active touch. J Neurophysiol 2016; 115:1797-809. [PMID: 26792880 DOI: 10.1152/jn.00465.2015] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2015] [Accepted: 01/15/2016] [Indexed: 11/22/2022] Open
Abstract
In the rodent whisker system, a key model for neural processing and behavioral choices during active sensing, whisker motion is increasingly recognized as only part of a broader motor repertoire employed by rodents during active touch. In particular, recent studies suggest whisker and head motions are tightly coordinated. However, conditions governing the selection and temporal organization of such coordinated sensing strategies remain poorly understood. We videographically reconstructed head and whisker motions of freely moving mice searching for a randomly located rewarded aperture, focusing on trials in which animals appeared to rapidly "correct" their trajectory under tactile guidance. Mice orienting after unilateral contact repositioned their whiskers similarly to previously reported head-turning asymmetry. However, whisker repositioning preceded head turn onsets and was not bilaterally symmetric. Moreover, mice selectively employed a strategy we term contact maintenance, with whisking modulated to counteract head motion and facilitate repeated contacts on subsequent whisks. Significantly, contact maintenance was not observed following initial contact with an aperture boundary, when the mouse needed to make a large corrective head motion to the front of the aperture, but only following contact by the same whisker field with the opposite aperture boundary, when the mouse needed to precisely align its head with the reward spout. Together these results suggest that mice can select from a diverse range of sensing strategies incorporating both knowledge of the task and whisk-by-whisk sensory information and, moreover, suggest the existence of high level control (not solely reflexive) of sensing motions coordinated between multiple body parts.
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Affiliation(s)
- Joseph B Schroeder
- Department of Biomedical Engineering, Boston University, Boston, Massachusetts
| | - Jason T Ritt
- Department of Biomedical Engineering, Boston University, Boston, Massachusetts
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65
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Hobbs JA, Towal RB, Hartmann MJZ. Spatiotemporal Patterns of Contact Across the Rat Vibrissal Array During Exploratory Behavior. Front Behav Neurosci 2016; 9:356. [PMID: 26778990 PMCID: PMC4700281 DOI: 10.3389/fnbeh.2015.00356] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2015] [Accepted: 12/08/2015] [Indexed: 11/13/2022] Open
Abstract
The rat vibrissal system is an important model for the study of somatosensation, but the small size and rapid speed of the vibrissae have precluded measuring precise vibrissal-object contact sequences during behavior. We used a laser light sheet to quantify, with 1 ms resolution, the spatiotemporal structure of whisker-surface contact as five naïve rats freely explored a flat, vertical glass wall. Consistent with previous work, we show that the whisk cycle cannot be uniquely defined because different whiskers often move asynchronously, but that quasi-periodic (~8 Hz) variations in head velocity represent a distinct temporal feature on which to lock analysis. Around times of minimum head velocity, whiskers protract to make contact with the surface, and then sustain contact with the surface for extended durations (~25-60 ms) before detaching. This behavior results in discrete temporal windows in which large numbers of whiskers are in contact with the surface. These "sustained collective contact intervals" (SCCIs) were observed on 100% of whisks for all five rats. The overall spatiotemporal structure of the SCCIs can be qualitatively predicted based on information about head pose and the average whisk cycle. In contrast, precise sequences of whisker-surface contact depend on detailed head and whisker kinematics. Sequences of vibrissal contact were highly variable, equally likely to propagate in all directions across the array. Somewhat more structure was found when sequences of contacts were examined on a row-wise basis. In striking contrast to the high variability associated with contact sequences, a consistent feature of each SCCI was that the contact locations of the whiskers on the glass converged and moved more slowly on the sheet. Together, these findings lead us to propose that the rat uses a strategy of "windowed sampling" to extract an object's spatial features: specifically, the rat spatially integrates quasi-static mechanical signals across whiskers during the period of sustained contact, resembling an "enclosing" haptic procedure.
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Affiliation(s)
- Jennifer A Hobbs
- Department of Physics and Astronomy, Northwestern University Evanston, IL, USA
| | - R Blythe Towal
- Department of Biomedical Engineering, Northwestern University Evanston, IL, USA
| | - Mitra J Z Hartmann
- Department of Biomedical Engineering, Northwestern UniversityEvanston, IL, USA; Department of Mechanical Engineering, Northwestern UniversityEvanston, IL, USA
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66
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Sofroniew NJ, Vlasov YA, Hires SA, Freeman J, Svoboda K. Neural coding in barrel cortex during whisker-guided locomotion. eLife 2015; 4. [PMID: 26701910 PMCID: PMC4764557 DOI: 10.7554/elife.12559] [Citation(s) in RCA: 65] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2015] [Accepted: 12/21/2015] [Indexed: 11/15/2022] Open
Abstract
Animals seek out relevant information by moving through a dynamic world, but sensory systems are usually studied under highly constrained and passive conditions that may not probe important dimensions of the neural code. Here, we explored neural coding in the barrel cortex of head-fixed mice that tracked walls with their whiskers in tactile virtual reality. Optogenetic manipulations revealed that barrel cortex plays a role in wall-tracking. Closed-loop optogenetic control of layer 4 neurons can substitute for whisker-object contact to guide behavior resembling wall tracking. We measured neural activity using two-photon calcium imaging and extracellular recordings. Neurons were tuned to the distance between the animal snout and the contralateral wall, with monotonic, unimodal, and multimodal tuning curves. This rich representation of object location in the barrel cortex could not be predicted based on simple stimulus-response relationships involving individual whiskers and likely emerges within cortical circuits. DOI:http://dx.doi.org/10.7554/eLife.12559.001 Mice are primarily nocturnal animals that rely on their whiskers to navigate dark underground burrows and winding corridors. When a whisker touches an object, cells called neurons at the base of the whiskers produce electrical signals that are relayed to other neurons in an area of the brain called the barrel cortex. However, it is not clear how information is encoded in these electrical signals, in part, because it is technically challenging to collect data about neuron activity and behavior while the mice move around. To overcome these difficulties, Sofroniew, Vlasov et al. used a touch-based (or 'tactile') virtual reality system to study how mice navigate along corridors. The system simulated the contact the whiskers would have with the walls of a winding corridor. This was achieved by moving the walls with motors while holding the mouse still enough to be able to measure the activity of neurons in the barrel cortex and observe the behavior of the animal. The experiments show that the electrical signals in the barrel cortex encode information about motion as well as the distance between the mouse and the wall. For example, some neurons in the barrel cortex were only activated when a mouse was a particular distance from the walls. The experiments suggest that the barrel cortex processes signals received from several whiskers to build an overall picture of the locations and shapes of objects. Sofroniew, Vlasov et al. also used a technique called optogenetics to deliberately activate particular neurons in a manner that mimics their activity patterns during interactions with walls. In the absence of walls, the optogenetic stimuli guided the behavior of the mice so that they tracked along the paths of 'illusory' corridors. Together, these findings reveal the neural code in the barrel cortex that allows mice to navigate by touch. DOI:http://dx.doi.org/10.7554/eLife.12559.002
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Affiliation(s)
| | - Yurii A Vlasov
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, United States.,IBM Thomas J. Watson Research Center, New York, United States
| | - Samuel Andrew Hires
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, United States
| | - Jeremy Freeman
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, United States
| | - Karel Svoboda
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, United States
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67
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Abstract
Eyes may be 'the window to the soul' in humans, but whiskers provide a better path to the inner lives of rodents. The brain has remarkable abilities to focus its limited resources on information that matters, while ignoring a cacophony of distractions. While inspecting a visual scene, primates foveate to multiple salient locations, for example mouths and eyes in images of people, and ignore the rest. Similar processes have now been observed and studied in rodents in the context of whisker-based tactile sensation. Rodents use their mechanosensitive whiskers for a diverse range of tactile behaviors such as navigation, object recognition and social interactions. These animals move their whiskers in a purposive manner to locations of interest. The shapes of whiskers, as well as their movements, are exquisitely adapted for tactile exploration in the dark tight burrows where many rodents live. By studying whisker movements during tactile behaviors, we can learn about the tactile information available to rodents through their whiskers and how rodents direct their attention. In this primer, we focus on how the whisker movements of rats and mice are providing clues about the logic of active sensation and the underlying neural mechanisms.
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68
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Motion makes sense: an adaptive motor-sensory strategy underlies the perception of object location in rats. J Neurosci 2015; 35:8777-89. [PMID: 26063912 DOI: 10.1523/jneurosci.4149-14.2015] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Tactile perception is obtained by coordinated motor-sensory processes. We studied the processes underlying the perception of object location in freely moving rats. We trained rats to identify the relative location of two vertical poles placed in front of them and measured at high resolution the motor and sensory variables (19 and 2 variables, respectively) associated with this whiskers-based perceptual process. We found that the rats developed stereotypic head and whisker movements to solve this task, in a manner that can be described by several distinct behavioral phases. During two of these phases, the rats' whiskers coded object position by first temporal and then angular coding schemes. We then introduced wind (in two opposite directions) and remeasured their perceptual performance and motor-sensory variables. Our rats continued to perceive object location in a consistent manner under wind perturbations while maintaining all behavioral phases and relatively constant sensory coding. Constant sensory coding was achieved by keeping one group of motor variables (the "controlled variables") constant, despite the perturbing wind, at the cost of strongly modulating another group of motor variables (the "modulated variables"). The controlled variables included coding-relevant variables, such as head azimuth and whisker velocity. These results indicate that consistent perception of location in the rat is obtained actively, via a selective control of perception-relevant motor variables.
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69
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Hires SA, Gutnisky DA, Yu J, O'Connor DH, Svoboda K. Low-noise encoding of active touch by layer 4 in the somatosensory cortex. eLife 2015; 4. [PMID: 26245232 PMCID: PMC4525079 DOI: 10.7554/elife.06619] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2015] [Accepted: 07/07/2015] [Indexed: 11/13/2022] Open
Abstract
Cortical spike trains often appear noisy, with the timing and number of spikes varying across repetitions of stimuli. Spiking variability can arise from internal (behavioral state, unreliable neurons, or chaotic dynamics in neural circuits) and external (uncontrolled behavior or sensory stimuli) sources. The amount of irreducible internal noise in spike trains, an important constraint on models of cortical networks, has been difficult to estimate, since behavior and brain state must be precisely controlled or tracked. We recorded from excitatory barrel cortex neurons in layer 4 during active behavior, where mice control tactile input through learned whisker movements. Touch was the dominant sensorimotor feature, with >70% spikes occurring in millisecond timescale epochs after touch onset. The variance of touch responses was smaller than expected from Poisson processes, often reaching the theoretical minimum. Layer 4 spike trains thus reflect the millisecond-timescale structure of tactile input with little noise.
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Affiliation(s)
- Samuel Andrew Hires
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, United States
| | - Diego A Gutnisky
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, United States
| | - Jianing Yu
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, United States
| | - Daniel H O'Connor
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, United States
| | - Karel Svoboda
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, United States
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70
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Adineh VR, Liu B, Rajan R, Yan W, Fu J. Multidimensional characterisation of biomechanical structures by combining Atomic Force Microscopy and Focused Ion Beam: A study of the rat whisker. Acta Biomater 2015; 21:132-41. [PMID: 25839121 DOI: 10.1016/j.actbio.2015.03.028] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2014] [Revised: 03/23/2015] [Accepted: 03/23/2015] [Indexed: 01/13/2023]
Abstract
Understanding the heterogeneity of biological structures, particularly at the micro/nano scale can offer insights valuable for multidisciplinary research in tissue engineering and biomimicry designs. Here we propose to combine nanocharacterisation tools, particularly Focused Ion Beam (FIB) and Atomic Force Microscopy (AFM) for three dimensional mapping of mechanical modulus and chemical signatures. The prototype platform is applied to image and investigate the fundamental mechanics of the rat face whiskers, a high-acuity sensor used to gain detailed information about the world. Grazing angle FIB milling was first applied to expose the interior cross section of the rat whisker sample, followed by a "lift-out" method to retrieve and position the target sample for further analyses. AFM force spectroscopy measurements revealed a non-uniform pattern of elastic modulus across the cross section, with a range from 0.8GPa to 13.5GPa. The highest elastic modulus was found at the outer cuticle region of the whisker, and values gradually decreased towards the interior cortex and medulla regions. Elemental mapping with EDS confirmed that the interior of the rat whisker is dominated by C, O, N, S, Cl and K, with a significant change of elemental distribution close to the exterior cuticle region. Based on these data, a novel comprehensive three dimensional (3D) elastic modulus model was constructed, and stress distributions under realistic conditions were investigated with Finite Element Analysis (FEA). The simulations could well account for the passive whisker deflections, with calculated resonant frequency as well as force-deflection for the whiskers being in good agreement with reported experimental data. Limitations and further applications are discussed for the proposed FIB/AFM approach, which holds good promise as a unique platform to gain insights on various heterogeneous biomaterials and biomechanical systems.
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Affiliation(s)
- Vahid Reza Adineh
- Department of Mechanical and Aerospace Engineering, Monash University, Clayton, VIC 3800, Australia
| | - Boyin Liu
- Department of Mechanical and Aerospace Engineering, Monash University, Clayton, VIC 3800, Australia
| | - Ramesh Rajan
- Department of Physiology, Monash University, Clayton, VIC 3800, Australia
| | - Wenyi Yan
- Department of Mechanical and Aerospace Engineering, Monash University, Clayton, VIC 3800, Australia
| | - Jing Fu
- Department of Mechanical and Aerospace Engineering, Monash University, Clayton, VIC 3800, Australia.
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71
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Ossato A, Vigolo A, Trapella C, Seri C, Rimondo C, Serpelloni G, Marti M. JWH-018 impairs sensorimotor functions in mice. Neuroscience 2015; 300:174-88. [PMID: 25987201 DOI: 10.1016/j.neuroscience.2015.05.021] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2015] [Revised: 05/04/2015] [Accepted: 05/09/2015] [Indexed: 02/01/2023]
Abstract
Naphthalen-1-yl-(1-pentylindol-3-yl)methanone (JWH-018) is a synthetic cannabinoid agonist illegally marketed in "Spice" and "herbal blend" for its psychoactive effect greater than those produced by cannabis. In rodents JWH-018 reproduces typical effects of (-)-Δ(9)-THC or Dronabinol® (Δ(9)-THC) such as hypothermia, analgesia, hypolocomotion and akinesia, while its effects on sensorimotor functions are still unknown. Therefore, the aim of the present study is to investigate the effect of acute administration of JWH-018 (0.01-6mg/kg i.p.) on sensorimotor functions in male CD-1 mice and to compare its effects with those caused by the administration of Δ(9)-THC (0.01-6mg/kg i.p.). A specific battery of behavioral tests were adopted to investigate effects of cannabinoid agonists on sensorimotor functions (visual, auditory, tactile) and neurological changes (convulsion, myoclonia, hyperreflexia) while video-tracking analysis was used to study spontaneous locomotion. JWH-018 administration inhibited sensorimotor responses at lower doses (0.01-0.1mg/kg), reduced spontaneous locomotion at intermediate/high doses (1-6mg/kg) and induced convulsions, myoclonia and hyperreflexia at high doses (6mg/kg). Similarly, administration of Δ(9)-THC reduced sensorimotor responses in mice but it did not inhibit spontaneous locomotion and it did not induce neurological alterations. All behavioral effects and neurological alterations were prevented by the administration of the selective CB1 receptor antagonist/inverse agonist 1-(2,4-dichlorophenyl)-5-(4-iodophenyl)-4-methyl-N-(piperidin-1-yl)-1H-pyrazole-3-carboxamide (AM 251). For the first time these data demonstrate that JWH-018 impairs sensorimotor responses in mice. This aspect should be carefully evaluated to better understand the potential danger that JWH-018 may pose to public health, with particular reference to decreased performance in driving and hazardous works.
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Affiliation(s)
- A Ossato
- Department of Life Sciences and Biotechnology (SVeB), University of Ferrara, Italy
| | - A Vigolo
- Department of Life Sciences and Biotechnology (SVeB), University of Ferrara, Italy
| | - C Trapella
- Department of Chemistry and Pharmaceutical Sciences, University of Ferrara, Italy
| | - C Seri
- Italian National Early Warning System, Drug Policies Department, Presidency of the Council of Ministers, Verona Coordination Unit, Italy
| | - C Rimondo
- Italian National Early Warning System, Drug Policies Department, Presidency of the Council of Ministers, Verona Coordination Unit, Italy; Department of Public Health and Community Medicine, University of Verona, Italy
| | - G Serpelloni
- Italian National Early Warning System, Drug Policies Department, Presidency of the Council of Ministers, Verona Coordination Unit, Italy
| | - M Marti
- Department of Life Sciences and Biotechnology (SVeB), University of Ferrara, Italy; Center for Neuroscience and Istituto Nazionale di Neuroscienze, Italy.
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72
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Peron SP, Freeman J, Iyer V, Guo C, Svoboda K. A Cellular Resolution Map of Barrel Cortex Activity during Tactile Behavior. Neuron 2015; 86:783-99. [PMID: 25913859 DOI: 10.1016/j.neuron.2015.03.027] [Citation(s) in RCA: 203] [Impact Index Per Article: 22.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2014] [Revised: 01/29/2015] [Accepted: 03/11/2015] [Indexed: 11/17/2022]
Abstract
Comprehensive measurement of neural activity remains challenging due to the large numbers of neurons in each brain area. We used volumetric two-photon imaging in mice expressing GCaMP6s and nuclear red fluorescent proteins to sample activity in 75% of superficial barrel cortex neurons across the relevant cortical columns, approximately 12,000 neurons per animal, during performance of a single whisker object localization task. Task-related activity peaked during object palpation. An encoding model related activity to behavioral variables. In the column corresponding to the spared whisker, 300 layer (L) 2/3 pyramidal neurons (17%) each encoded touch and whisker movements. Touch representation declined by half in surrounding columns; whisker movement representation was unchanged. Following the emergence of stereotyped task-related movement, sensory representations showed no measurable plasticity. Touch direction was topographically organized, with distinct organization for passive and active touch. Our work reveals sparse and spatially intermingled representations of multiple tactile features. VIDEO ABSTRACT.
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Affiliation(s)
- Simon P Peron
- Janelia Research Campus, Howard Hughes Medical Institute, 19700 Helix Drive, Ashburn, VA 20147, USA
| | - Jeremy Freeman
- Janelia Research Campus, Howard Hughes Medical Institute, 19700 Helix Drive, Ashburn, VA 20147, USA
| | - Vijay Iyer
- Janelia Research Campus, Howard Hughes Medical Institute, 19700 Helix Drive, Ashburn, VA 20147, USA
| | - Caiying Guo
- Janelia Research Campus, Howard Hughes Medical Institute, 19700 Helix Drive, Ashburn, VA 20147, USA
| | - Karel Svoboda
- Janelia Research Campus, Howard Hughes Medical Institute, 19700 Helix Drive, Ashburn, VA 20147, USA.
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73
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Huet LA, Schroeder CL, Hartmann MJZ. Tactile signals transmitted by the vibrissa during active whisking behavior. J Neurophysiol 2015; 113:3511-8. [PMID: 25867739 DOI: 10.1152/jn.00011.2015] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2015] [Accepted: 03/30/2015] [Indexed: 11/22/2022] Open
Abstract
The rodent vibrissal-trigeminal system is one of the most widely used models for the study of somatosensation and tactile perception, but to date the field has been unable to quantify the complete set of mechanical input signals generated during natural whisking behavior. In this report we show that during whisking behavior of awake rats (Rattus norvegicus), the whisker will often bend out of its plane of rotation, generating sizeable mechanical (tactile) signals out of the plane. We then develop a model of whisker bending that allows us to compute the three-dimensional tactile signals at the vibrissal base during active whisking behavior. Considerable information can be lost if whisking motions are considered only in two dimensions, and we offer some suggestions for experimentalists concerned with monitoring the direction of bending. These data represent the first quantification of the physical signals transmitted to the mechanoreceptors in the follicle during active whisking behavior.
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Affiliation(s)
- Lucie A Huet
- Department of Mechanical Engineering, Northwestern University, Evanston, Illinois; and
| | | | - Mitra J Z Hartmann
- Department of Mechanical Engineering, Northwestern University, Evanston, Illinois; and Department of Biomedical Engineering, Northwestern University, Evanston, Illinois
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74
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Lottem E, Gugig E, Azouz R. Parallel coding schemes of whisker velocity in the rat's somatosensory system. J Neurophysiol 2014; 113:1784-99. [PMID: 25552637 DOI: 10.1152/jn.00485.2014] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The function of rodents' whisker somatosensory system is to transform tactile cues, in the form of vibrissa vibrations, into neuronal responses. It is well established that rodents can detect numerous tactile stimuli and tell them apart. However, the transformation of tactile stimuli obtained through whisker movements to neuronal responses is not well-understood. Here we examine the role of whisker velocity in tactile information transmission and its coding mechanisms. We show that in anaesthetized rats, whisker velocity is related to the radial distance of the object contacted and its own velocity. Whisker velocity is accurately and reliably coded in first-order neurons in parallel, by both the relative time interval between velocity-independent first spike latency of rapidly adapting neurons and velocity-dependent first spike latency of slowly adapting neurons. At the same time, whisker velocity is also coded, although less robustly, by the firing rates of slowly adapting neurons. Comparing first- and second-order neurons, we find similar decoding efficiencies for whisker velocity using either temporal or rate-based methods. Both coding schemes are sufficiently robust and hardly affected by neuronal noise. Our results suggest that whisker kinematic variables are coded by two parallel coding schemes and are disseminated in a similar way through various brain stem nuclei to multiple brain areas.
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Affiliation(s)
- Eran Lottem
- Department of Physiology and Cell Biology, Zlotowski Center for Neuroscience, Ben-Gurion University of the Negev, Beer-Sheva, Israel
| | - Erez Gugig
- Department of Physiology and Cell Biology, Zlotowski Center for Neuroscience, Ben-Gurion University of the Negev, Beer-Sheva, Israel
| | - Rony Azouz
- Department of Physiology and Cell Biology, Zlotowski Center for Neuroscience, Ben-Gurion University of the Negev, Beer-Sheva, Israel
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75
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Modeling forces and moments at the base of a rat vibrissa during noncontact whisking and whisking against an object. J Neurosci 2014; 34:9828-44. [PMID: 25057187 DOI: 10.1523/jneurosci.1707-12.2014] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
During exploratory behavior, rats brush and tap their whiskers against objects, and the mechanical signals so generated constitute the primary sensory variables upon which these animals base their vibrissotactile perception of the world. To date, however, we lack a general dynamic model of the vibrissa that includes the effects of inertia, damping, and collisions. We simulated vibrissal dynamics to compute the time-varying forces and bending moment at the vibrissa base during both noncontact (free-air) whisking and whisking against an object (collision). Results show the following: (1) during noncontact whisking, mechanical signals contain components at both the whisking frequency and also twice the whisking frequency (the latter could code whisking speed); (2) when rats whisk rhythmically against an object, the intrinsic dynamics of the vibrissa can be as large as many of the mechanical effects of the collision, however, the axial force could still generate responses that reliably indicate collision based on thresholding; and (3) whisking velocity will have only a small effect on the transient response generated during a whisker-object collision. Instead, the transient response will depend in large part on how the rat chooses to decelerate its vibrissae after the collision. The model allows experimentalists to estimate error bounds on quasi-static descriptions of vibrissal shape, and its predictions can be used to bound realistic expectations from neurons that code vibrissal sensing. We discuss the implications of these results under the assumption that primary sensory neurons of the trigeminal ganglion are sensitive to various combinations of mechanical signals.
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76
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Abstract
During many natural behaviors the relevant sensory stimuli and motor outputs are difficult to quantify. Furthermore, the high dimensionality of the space of possible stimuli and movements compounds the problem of experimental control. Head fixation facilitates stimulus control and movement tracking, and can be combined with techniques for recording and manipulating neural activity. However, head-fixed mouse behaviors are typically trained through extensive instrumental conditioning. Here we present a whisker-based, tactile virtual reality system for head-fixed mice running on a spherical treadmill. Head-fixed mice displayed natural movements, including running and rhythmic whisking at 16 Hz. Whisking was centered on a set point that changed in concert with running so that more protracted whisking was correlated with faster running. During turning, whiskers moved in an asymmetric manner, with more retracted whisker positions in the turn direction and protracted whisker movements on the other side. Under some conditions, whisker movements were phase-coupled to strides. We simulated a virtual reality tactile corridor, consisting of two moveable walls controlled in a closed-loop by running speed and direction. Mice used their whiskers to track the walls of the winding corridor without training. Whisker curvature changes, which cause forces in the sensory follicles at the base of the whiskers, were tightly coupled to distance from the walls. Our behavioral system allows for precise control of sensorimotor variables during natural tactile navigation.
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77
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Maravall M, Diamond ME. Algorithms of whisker-mediated touch perception. Curr Opin Neurobiol 2014; 25:176-86. [PMID: 24549178 DOI: 10.1016/j.conb.2014.01.014] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2014] [Accepted: 01/23/2014] [Indexed: 11/18/2022]
Abstract
Comparison of the functional organization of sensory modalities can reveal the specialized mechanisms unique to each modality as well as processing algorithms that are common across modalities. Here we examine the rodent whisker system. The whisker's mechanical properties shape the forces transmitted to specialized receptors. The sensory and motor systems are intimately interconnected, giving rise to two forms of sensation: generative and receptive. The sensory pathway is a test bed for fundamental concepts in computation and coding: hierarchical feature detection, sparseness, adaptive representations, and population coding. The central processing of signals can be considered a sequence of filters. At the level of cortex, neurons represent object features by a coordinated population code which encompasses cells with heterogeneous properties.
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Affiliation(s)
- Miguel Maravall
- Instituto de Neurociencias de Alicante UMH-CSIC, Campus de San Juan, Apartado 18, 03550 Sant Joan d'Alacant, Spain
| | - Mathew E Diamond
- Tactile Perception and Learning Lab, International School for Advanced Studies-SISSA, Via Bonomea 265, 34136 Trieste, Italy.
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78
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Guo ZV, Hires SA, Li N, O'Connor DH, Komiyama T, Ophir E, Huber D, Bonardi C, Morandell K, Gutnisky D, Peron S, Xu NL, Cox J, Svoboda K. Procedures for behavioral experiments in head-fixed mice. PLoS One 2014; 9:e88678. [PMID: 24520413 PMCID: PMC3919818 DOI: 10.1371/journal.pone.0088678] [Citation(s) in RCA: 249] [Impact Index Per Article: 24.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2013] [Accepted: 12/14/2013] [Indexed: 12/03/2022] Open
Abstract
The mouse is an increasingly prominent model for the analysis of mammalian neuronal circuits. Neural circuits ultimately have to be probed during behaviors that engage the circuits. Linking circuit dynamics to behavior requires precise control of sensory stimuli and measurement of body movements. Head-fixation has been used for behavioral research, particularly in non-human primates, to facilitate precise stimulus control, behavioral monitoring and neural recording. However, choice-based, perceptual decision tasks by head-fixed mice have only recently been introduced. Training mice relies on motivating mice using water restriction. Here we describe procedures for head-fixation, water restriction and behavioral training for head-fixed mice, with a focus on active, whisker-based tactile behaviors. In these experiments mice had restricted access to water (typically 1 ml/day). After ten days of water restriction, body weight stabilized at approximately 80% of initial weight. At that point mice were trained to discriminate sensory stimuli using operant conditioning. Head-fixed mice reported stimuli by licking in go/no-go tasks and also using a forced choice paradigm using a dual lickport. In some cases mice learned to discriminate sensory stimuli in a few trials within the first behavioral session. Delay epochs lasting a second or more were used to separate sensation (e.g. tactile exploration) and action (i.e. licking). Mice performed a variety of perceptual decision tasks with high performance for hundreds of trials per behavioral session. Up to four months of continuous water restriction showed no adverse health effects. Behavioral performance correlated with the degree of water restriction, supporting the importance of controlling access to water. These behavioral paradigms can be combined with cellular resolution imaging, random access photostimulation, and whole cell recordings.
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Affiliation(s)
- Zengcai V. Guo
- Janelia Farm Research Campus, Howard Hughes Medical Institute, Ashburn, Virginia, United States of America
| | - S. Andrew Hires
- Janelia Farm Research Campus, Howard Hughes Medical Institute, Ashburn, Virginia, United States of America
| | - Nuo Li
- Janelia Farm Research Campus, Howard Hughes Medical Institute, Ashburn, Virginia, United States of America
| | - Daniel H. O'Connor
- Janelia Farm Research Campus, Howard Hughes Medical Institute, Ashburn, Virginia, United States of America
| | - Takaki Komiyama
- Janelia Farm Research Campus, Howard Hughes Medical Institute, Ashburn, Virginia, United States of America
| | - Eran Ophir
- Janelia Farm Research Campus, Howard Hughes Medical Institute, Ashburn, Virginia, United States of America
| | - Daniel Huber
- Janelia Farm Research Campus, Howard Hughes Medical Institute, Ashburn, Virginia, United States of America
- Department of Basic Neurosciences, University of Geneva, Geneva, Switzerland
| | - Claudia Bonardi
- Department of Basic Neurosciences, University of Geneva, Geneva, Switzerland
| | - Karin Morandell
- Department of Basic Neurosciences, University of Geneva, Geneva, Switzerland
| | - Diego Gutnisky
- Janelia Farm Research Campus, Howard Hughes Medical Institute, Ashburn, Virginia, United States of America
| | - Simon Peron
- Janelia Farm Research Campus, Howard Hughes Medical Institute, Ashburn, Virginia, United States of America
| | - Ning-long Xu
- Janelia Farm Research Campus, Howard Hughes Medical Institute, Ashburn, Virginia, United States of America
| | - James Cox
- Janelia Farm Research Campus, Howard Hughes Medical Institute, Ashburn, Virginia, United States of America
| | - Karel Svoboda
- Janelia Farm Research Campus, Howard Hughes Medical Institute, Ashburn, Virginia, United States of America
- * E-mail:
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79
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Mongeau JM, Demir A, Dallmann CJ, Jayaram K, Cowan NJ, Full RJ. Mechanical processing via passive dynamic properties of the cockroach antenna can facilitate control during rapid running. J Exp Biol 2014; 217:3333-45. [DOI: 10.1242/jeb.101501] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Abstract
The integration of information from dynamic sensory structures operating on a moving body is a challenge for locomoting animals and engineers seeking to design agile robots. As a tactile sensor is a physical linkage mediating mechanical interactions between body and environment, mechanical tuning of the sensor is critical for effective control. We determined the open-loop dynamics of a tactile sensor, specifically the antenna of the American cockroach, Periplaneta americana, an animal that escapes predators by using its antennae during rapid closed-loop tactilely mediated course control. Geometrical measurements and static bending experiments revealed an exponentially decreasing flexural stiffness (EI) from base to tip. Quasi-static experiments with a physical model support the hypothesis that a proximodistally decreasing EI can simplify control by increasing preview distance and allowing effective mapping to a putative control variable - body-to-wall distance - compared to an antenna with constant EI. We measured the free response at the tip of the antenna following step deflections and determined that the antenna rapidly damps large deflections: over 90% of the perturbation is rejected within the first cycle, corresponding to almost one stride period during high-speed running (~50 ms). An impulse-like perturbation near the tip revealed dynamics that were characteristic of an inelastic collision, keeping the antenna in contact with an object after impact. We contend that proximodistally decreasing stiffness, high damping, and inelasticity simplify control during high-speed tactile tasks by increasing preview distance, providing a one-dimensional map between antennal bending and body-to-wall distance, and increasing the reliability of tactile information.
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80
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Abstract
Perceptual decisions involve distributed cortical activity. Does information flow sequentially from one cortical area to another, or do networks of interconnected areas contribute at the same time? Here we delineate when and how activity in specific areas drives a whisker-based decision in mice. A short-term memory component temporally separated tactile "sensation" and "action" (licking). Using optogenetic inhibition (spatial resolution, 2 mm; temporal resolution, 100 ms), we surveyed the neocortex for regions driving behavior during specific behavioral epochs. Barrel cortex was critical for sensation. During the short-term memory, unilateral inhibition of anterior lateral motor cortex biased responses to the ipsilateral side. Consistently, barrel cortex showed stimulus-specific activity during sensation, whereas motor cortex showed choice-specific preparatory activity and movement-related activity, consistent with roles in motor planning and movement. These results suggest serial information flow from sensory to motor areas during perceptual decision making.
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81
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Abstract
Many mammals forage and burrow in dark constrained spaces. Touch through facial whiskers is important during these activities, but the close quarters makes whisker deployment challenging. The diverse shapes of facial whiskers reflect distinct ecological niches. Rodent whiskers are conical, often with a remarkably linear taper. Here we use theoretical and experimental methods to analyze interactions of mouse whiskers with objects. When pushed into objects, conical whiskers suddenly slip at a critical angle. In contrast, cylindrical whiskers do not slip for biologically plausible movements. Conical whiskers sweep across objects and textures in characteristic sequences of brief sticks and slips, which provide information about the tactile world. In contrast, cylindrical whiskers stick and remain stuck, even when sweeping across fine textures. Thus the conical whisker structure is adaptive for sensor mobility in constrained environments and in feature extraction during active haptic exploration of objects and surfaces. DOI:http://dx.doi.org/10.7554/eLife.01350.001 When foraging in dark, confined spaces, mammals use the information gathered by their whiskers to ‘see’ the world around them. Mammalian whiskers come in a variety of shapes and sizes, most likely reflecting the way in which they are used. Rodent whiskers are conical and precisely tapered, whereas some harbor seals have flattened whiskers with wave-like undulations. Human hair is cylindrical. Rodents sweep their whiskers back and forth over objects and surfaces without moving their head. They use this process, called whisking, to build up a three-dimensional picture of objects. Whisking allows the rodent to estimate where an object is located, how big it is, and what kind of surface texture it has. Information about surface texture can, for example, help the animal to distinguish a stone from a seed. Hires et al. have used theoretical and experimental methods to analyze the interaction of mouse whiskers with objects. The conical shape of a mouse whisker makes the tip thousands of times more flexible than the base. Hires et al. show that this flexibility gradient allows the whiskers to slip past objects close to the face and to move freely across rough surfaces. Cylindrical whiskers, on the other hand, become stuck behind nearby objects and get caught on tiny features in an object’s surface texture. Hires et al. conclude that conical whiskers are advantageous in the tight confines of the tunnels that mice live, forage and socialize in, because they are able to gather a more complete sensory picture of their surroundings. The maneuverability of the whiskers also allows the mouse to move their whiskers forwards or backwards when rough tunnel walls are close by. By contrast, the sticking experienced by cylindrical whiskers would lead to ‘blind spots’. In addition to providing insights into the ways that mice interact with their environment, this work could also lead to improvements in the design of the canes used by the visually impaired to navigate human environments. DOI:http://dx.doi.org/10.7554/eLife.01350.002
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Affiliation(s)
- Samuel Andrew Hires
- Janelia Farm Research Campus, Howard Hughes Medical Institute, Ashburn, United States
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82
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O'Connor DH, Hires SA, Guo ZV, Li N, Yu J, Sun QQ, Huber D, Svoboda K. Neural coding during active somatosensation revealed using illusory touch. Nat Neurosci 2013; 16:958-65. [PMID: 23727820 PMCID: PMC3695000 DOI: 10.1038/nn.3419] [Citation(s) in RCA: 190] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2013] [Accepted: 05/05/2013] [Indexed: 12/14/2022]
Abstract
Active sensation requires the convergence of external stimuli with representations of body movements. We used mouse behavior, electrophysiology and optogenetics to dissect the temporal interactions among whisker movement, neural activity and sensation of touch. We photostimulated layer 4 activity in single barrels in a closed loop with whisking. Mimicking touch-related neural activity caused illusory perception of an object at a particular location, but scrambling the timing of the spikes over one whisking cycle (tens of milliseconds) did not abolish the illusion, indicating that knowledge of instantaneous whisker position is unnecessary for discriminating object locations. The illusions were induced only during bouts of directed whisking, when mice expected touch, and in the relevant barrel. Reducing activity biased behavior, consistent with a spike count code for object detection at a particular location. Our results show that mice integrate coding of touch with movement over timescales of a whisking bout to produce perception of active touch.
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Affiliation(s)
- Daniel H O'Connor
- Janelia Farm Research Campus, Howard Hughes Medical Institute, Ashburn, Virginia, USA
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83
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Pre-neuronal morphological processing of object location by individual whiskers. Nat Neurosci 2013; 16:622-31. [PMID: 23563582 DOI: 10.1038/nn.3378] [Citation(s) in RCA: 76] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2012] [Accepted: 03/11/2013] [Indexed: 11/08/2022]
Abstract
In the vibrissal system, touch information is conveyed by a receptorless whisker hair to follicle mechanoreceptors, which then provide input to the brain. We examined whether any processing, that is, meaningful transformation, occurs in the whisker itself. Using high-speed videography and tracking the movements of whiskers in anesthetized and behaving rats, we found that whisker-related morphological phase planes, based on angular and curvature variables, can represent the coordinates of object position after contact in a reliable manner, consistent with theoretical predictions. By tracking exposed follicles, we found that the follicle-whisker junction is rigid, which enables direct readout of whisker morphological coding by mechanoreceptors. Finally, we found that our behaving rats pushed their whiskers against objects during localization in a way that induced meaningful morphological coding and, in parallel, improved their localization performance, which suggests a role for pre-neuronal morphological computation in active vibrissal touch.
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