Research Overview

resprog For the latest publications please see the publications page, or my CV, for my publication metrics please see my Google Scholar profile.

For our research into legged systems, we aim to discover how the neural, muscular, and skeletal components of an organism work together to produce locomotion. This research is of fundamental importance in medicine (how can we improve the lives of those living with spinal cord injuries, patients with neurological disease, or amputees?), engineering (how do we build more agile robots?), basic biology (how has evolution shaped animal movement?), and veterinary science (how do we treat lameness, and create safe environments for animals?). We take an integrative approach that fuses experimental neuroscience, genetic tools, new instrumentation, and mathematical and physical (robot) models. Much of our past work in legged systems focused on how many-legged (>2) animals handle different surfaces.

In recent years we have developed a new focus on spinal cord injury. Specifically, we seek to understand how stimulation of sensory nerves with rehabilitation after injury improves recovery, referred to as electrical epidural stimulation. Working the rat model, we are using cutting edge genetic tools (DREADDs) to activate or suppress afferent activity while animals run on a treadmill. These tools allow us to target specific neurons and activate them remotely with drug delivery, and then trace the activated neurons with histological methods, dissecting the helpful plasticity that occurs in spinal cord circuits.

A long term focus on the lab has been a dynamical systems approach to quadrupedal gaits. In dogs, horses and spiders we are developing tools to quantify gaits, and how animals choose gaits. With these new tools, we have found that gait transitions are remarkably stereotyped. Formulating a dynamical systems model of quadrupedal gait, we found that dogs walking outside on natural rough terrain adjust their gait towards the idealised trot. They further allowed analysis of limping in spiders that have lost legs, demonstrating their mechanisms of robustness. Finally, other groups have started using these tools to analyze the gaits of spinal cord injured animals, giving better insight into how neural circuitry is affected.

Finally, we have a thread of research focused on the biomechanics and evolution of gliding. This has been a long term collaboration with Dr. Greg Byrnes.

Research By Project/Grant

dreadds ees PA CURE Spinal Cord Research Program - Enhancing rehabilitation effectiveness with coactivation of corticospinal neurons.
Enhancing rehabilitation effectiveness with coactivation of corticospinal neurons.

Spinal cord injuries (SCI) affect approximately 100,000 patients each year, causing motor, sensory and autonomic dysfunction. Approximately 55% of all SCIs occur at the cervical level in human patients, effecting forelimb function (National Spinal Cord Injury Statistical Center, 2017). Patients effected by a cervical SCI desire recovery of hand and digit function to improve their lifestyle. Since spontaneous regeneration does not occur within the central nervous system, sprouting or plasticity within descending motor circuits is the primary driver of functional recovery after SCI. Understanding the key intersection points of plasticity within these circuits supporting functional recovery can help identify targets for developing new therapies to enhance recovery after spinal cord injury. Here we will use chemogenetic tools to modulate cortical activity and drive plasticity during remodeling of neural circuits during rehabilitation. This study will provide key insight into how circuits adapt to the injury during rehabilitation and how cortical activity can influence the extent of this recovery.

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dreadds ees NIH NINDS R01 Chemogenetic afferent modulation to understand spinal cord circuit function and plasticity post injury
Uncovering the mechanisms of improved recovery from spinal cord injury

Spinal cord injury (SCI) causes life-long neurological impairment, and there is currently no effective treatment. The premise of this proposal is recent work demonstrating that afferent stimulation paired with treadmill training can enhance standing, stepping, and volitional control in humans and animal models. Therefore, it is critically important to understand the mechanisms by which afferent stimulation drives motor improvement. Tools that can identify which afferents are necessary and sufficient to enhance recovery, and that can facilitate characterization of the helpful neural plasticity, are urgently needed. Our long-term goal is to develop approaches for selective afferent modulation, and apply them to the dissection of the mechanisms underlying recovery from SCI. The objective of this grant is to identify which sets of afferents are important for recovery and how spinal circuits change to facilitate it. To achieve selective modulation of afferents and enable genetic tracing we will use Designer Receptors Exclusively Activated by Designer Drugs (DREADDs) that can modulate excitability in specific populations of neurons. To accurately quantify improvement, we will use Deep Learning to analyze large kinematic data sets. Our preliminary data shows strong expression of DREADDs in large diameter DRG neurons, that their activation by CNO can excite or inhibit the H-reflex, and that activation of excitatory DREADDs during treadmill training post-SCI improves stepping. Our main hypothesis is that activation of large afferents by the excitatory DREADD (hM3Dq) during treadmill training will enhance recovery, whereas inhibitory DREADDs (hM4Di) will suppress recovery. Four sub- hypotheses will test whether recovery is mediated by increased afferent projection onto 1) motor neurons, or 2) inhibitory interneurons; or by sprouting of 3) reticulospinal and 4) propriospinal circuits. Our Specific Aims are to determine whether selective expression of DREADDs in (Aim 1) all large diameter (proprioceptive and tactile) neurons and (Aim 2) large proprioceptive afferents only can enhance recovery. The rationale for these aims is that afferent stimulation is hypothesized to work through selective excitation of large diameter sensory afferents (LDSA) that both drive motor pools locally and facilitate proprio- and surpraspinal input. To date, it has not been possible to definitively determine which afferents were recruited after electrical stimulation, or to select between afferents of similar diameter. The significance of this work lies in determining whether recovery is mediated exclusively by proprioceptive axons or a combination of proprioceptive and tactile afferents, and uncovering the mechanisms of functional plasticity in the spinal cord.

  • Chemogenetic modulation of sensory afferents induces locomotor changes and plasticity after spinal cord injury.
    Frontiers in Molecular Neuroscience - Neuroplasticity and Development Special Topic 26 August 2022
    Jaclyn T. Eisdorfer, Hannah Sobotka-Briner, Susan Schramfield, George Moukarzel, Jie Chen, Thomas Campion, Rupert Smit, Bradley C. Rauscher, Michel A. Lemay, George M. Smith, Andrew J. Spence.
  • Epidural Electrical Stimulation: A Review of Plasticity Mechanisms That Are Hypothesized to Underlie Enhanced Recovery From Spinal Cord Injury With Stimulation. 2 Sept. 2020. Frontiers in Molecular Neuroscience. 2 September 2020.
    Jaclyn T. Eisdorfer, Rupert D. Smit, Kathleen M. Keefe, Michel A. Lemay, George M. Smith and Andrew J. Spence
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    dreadds ees NIH CNNT R01 Adaptation of internal motor copy circuits in recovery after spinal cord injury.
    Adaptation of internal motor copy circuits in recovery after spinal cord injury.

    Cervical injury to the spinal cord results in dimished forelimb function. The Smith lab recently identified that the C3-C4 propriospinal neurons, which connect to the lateral reticular nucleus, can promote recovery of forelimb function after cervical lesions and rehabilitative training. We hypothesized that rehabilitation promotes recovery by inducing sprouting along the propriospinal-lateral reticular formation-cerebellar-brainstem loop and important pathway that normal functions to correct forelimb-patterning errors during the movement. The Spence group is excited to add kinematic tracking of forelimb reaching tasks in rats for this project, and to develop motor control relevant models of this behavior.

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    dreadds ees Craig H. Neilsen Foundation Senior Research Grant - Can chemogenetic afferent stimulation enhance recovery from SCI?
    Can chemogenetic afferent stimulation enhance recovery from SCI?

    The goal of this Craig H. Neilsen proposal was to selectively target only proprioceptive afferents during rehabilitation in rats, to determine whether this is as effective as stimuilating all large diameter afferents. To date, it has not been possible to definitively determine which afferents were recruited after electrical stimulation, or to select between afferents of similar diameter. The significance of this work lies in determining whether recovery is mediated exclusively by proprioceptive axons or a combination of proprioceptive and tactile afferents, and uncovering the mechanisms of functional plasticity in the spinal cord.

  • Chemogenetic modulation of sensory afferents induces locomotor changes and plasticity after spinal cord injury.
    Frontiers in Molecular Neuroscience - Neuroplasticity and Development Special Topic 26 August 2022
    Jaclyn T. Eisdorfer, Hannah Sobotka-Briner, Susan Schramfield, George Moukarzel, Jie Chen, Thomas Campion, Rupert Smit, Bradley C. Rauscher, Michel A. Lemay, George M. Smith, Andrew J. Spence.
  • Epidural Electrical Stimulation: A Review of Plasticity Mechanisms That Are Hypothesized to Underlie Enhanced Recovery From Spinal Cord Injury With Stimulation. 2 Sept. 2020. Frontiers in Molecular Neuroscience. 2 September 2020.
    Jaclyn T. Eisdorfer, Rupert D. Smit, Kathleen M. Keefe, Michel A. Lemay, George M. Smith and Andrew J. Spence
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    dreadds ees Shriners Hospitals For Children Research Grant - Chemogenetic Afferent Modulation to Improve Recovery from SCI
    Chemogenetic Afferent Modulation to Improve Recovery from SCI

    This Shriners grant was the launching point for our SCI research program - seeking to activate large diameter sensory afferents in the rat model of spinal cord injury, we are looking to uncover the mechanisms by which these treatments help regain function after injury. This early grant sought to activate all large diameter afferents with DREADDs.

  • Chemogenetic modulation of sensory afferents induces locomotor changes and plasticity after spinal cord injury.
    Frontiers in Molecular Neuroscience - Neuroplasticity and Development Special Topic 26 August 2022
    Jaclyn T. Eisdorfer, Hannah Sobotka-Briner, Susan Schramfield, George Moukarzel, Jie Chen, Thomas Campion, Rupert Smit, Bradley C. Rauscher, Michel A. Lemay, George M. Smith, Andrew J. Spence.
  • Epidural Electrical Stimulation: A Review of Plasticity Mechanisms That Are Hypothesized to Underlie Enhanced Recovery From Spinal Cord Injury With Stimulation. 2 Sept. 2020. Frontiers in Molecular Neuroscience. 2 September 2020.
    Jaclyn T. Eisdorfer, Rupert D. Smit, Kathleen M. Keefe, Michel A. Lemay, George M. Smith and Andrew J. Spence
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    NMOPTO Army Research Office (ARO) — NOFALL: Neuromechanics and Optogenetics: Dissecting Fast Legged Locomotion
    NOFALL: Neuromechanics and Optogenetics: Dissecting Fast Legged Locomotion

    The goal of this grant was to develop theoretical, robotic, and genetic tools to tackle long standing questions in motor control, in the mouse genetic model organism. Using a robotic "earthquake" treadmill, we uncovered the structure of the mouse gait controller, and laid foundations for optical and electrical neural perturbations with a novel, simple magnetic headmount.

  • A versatile system for neuromuscular stimulation and recording in the mouse model using a lightweight magnetically coupled headmount.
    Journal of Neuroscience Methods 1 October 2021.
    Annie Vahedipour, Matthew R.Short, Azadeh Timnak, Omid Haji Maghsoudi, Thomas Hallowell, Jonathan Gerstenhaber, Ornella Cappellari, Michel Lemay, Andrew J.Spence.
  • A novel method for robust markerless tracking of rodent paws in 3D.
    URASIP Journal on Image and Video Processing. 14 September 2019.
    Omid Haji Maghsoudi, Annie Vahedipour, and Spence, A. J.
  • Uncovering the structure of the mouse gait controller: mice respond to substrate perturbations with adaptations in gait on a continuum between trot and bound.
    Journal of Biomechanics 78 pp. 77-86. September 10th, 2018.
    Vahedipour, A., Haji-Maghsoudi, O., Wilshin, S., Shamble, P., Robertson, B. D. and Spence, A. J.
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    NMOPTO BBSRC — Foundations of Neuromechanical Systems Biology
    BBSRC — Foundations of Neuromechanical Systems Biology

    The goal of this grant was to develop instrumentation and experimental tools to tackle long standing questions in the control of locomotion, in the mouse genetic model organism. We published a closed-loop treadmill system for perturbing freely running small animals, that became the foundation for many more studies, and with our co-investigators on the grant, John Hutchinson and Nic Wells, we published two highly cited papers with a detailed computational musculoskeletal model of the mouse hindlimb.

  • Musculoskeletal Geometry, Muscle Architecture and Functional Specialisations of the Mouse Hindlimb.
    PLoS ONE (2016) 11 (4): e147669. April 26th, 2016.
    Charles, J.P., O. Cappellari, A.J. Spence, J.R. Hutchinson and D.J. Wells.
  • Muscle moment arms and sensitivity analysis of a mouse hindlimb musculoskeletal model.
    Journal of Anatomy (2016) 229 (4) 514-535.
    Charles, J.P., O. Cappellari, A.J. Spence, D.J. Wells and J.R. Hutchinson.
  • Uncovering the structure of the mouse gait controller: mice respond to substrate perturbations with adaptations in gait on a continuum between trot and bound.
    Journal of Biomechanics 78 pp. 77-86. September 10th, 2018.
    Vahedipour, A., Haji-Maghsoudi, O., Wilshin, S., Shamble, P., Robertson, B. D. and Spence, A. J.
  • Closing the loop in legged neuromechanics: an open-source computer vision controlled treadmill.
    Journal of Neuroscience Methods (2013) 215 (2): 164–169. 15 May 2013.
    A.J. Spence, G. Nicholson-Thomas & R. Lampe.
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    running cockroach with backpack Royal Society — Closing the loop in legged neuromechanics
    xrl robot EPSRC — Bioinspired Control Architectures for Multileggd Locomotion

    Research By Topic

    Click on each topic for a more detailed description
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    Spinal Cord Injury

    Mechanisms of helpful plasticity after spinal cord injury
    Mechanisms of helpful plasticity after spinal cord injury

    draftAs a group we are excited to be working in the area of spinal cord injury. Broadly speaking, we seek to understand how treatment methods such as epidural stimulation or other modulation of the nervous system can improve recovery from an injury. Working in the rat model of spinal cord injury, we use kinematic data, robotic systems, genetic tools, and electrophysilogy to try to understand how neuronal circuitry can change in helpful ways so that persons living with spinal cord injury may have a higher quality of life.

  • Chemogenetic modulation of sensory afferents induces locomotor changes and plasticity after spinal cord injury.
    Frontiers in Molecular Neuroscience - Neuroplasticity and Development Special Topic 26 August 2022
    Jaclyn T. Eisdorfer, Hannah Sobotka-Briner, Susan Schramfield, George Moukarzel, Jie Chen, Thomas Campion, Rupert Smit, Bradley C. Rauscher, Michel A. Lemay, George M. Smith, Andrew J. Spence.
  • Epidural Electrical Stimulation: A Review of Plasticity Mechanisms That Are Hypothesized to Underlie Enhanced Recovery From Spinal Cord Injury With Stimulation. 2 Sept. 2020. Frontiers in Molecular Neuroscience. 2 September 2020.
    Jaclyn T. Eisdorfer, Rupert D. Smit, Kathleen M. Keefe, Michel A. Lemay, George M. Smith and Andrew J. Spence
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    Instrumentation, Devices, Computer Vision, Imaging, and Robotics

    Neural interfacing, robotics, software, imaging, and microdevices for neuromechanics and organismal biology
    Neural interfacing, robotics, software, imaging, and microdevices for neuromechanics and organismal biology

    draftTwo of the major limitations in experimental biology are 1) obtaining detailed data from intact, freely behaving animals in their natural environment, and 2) placing measurements of one part of an animal in the full context of the rest of the animal. With the first problem, we desire naturalistic stimuli to ensure that our explanations of function are both relevant to the animal's biology, and not artifact. For the second, the problem is that the function of any one organ within an animal is intertwined with the rest of the animal; the more we can do to simultanously monitor multiple parts of the animal, the better our explanations of organ function can be. To these ends, we have worked to develop sensor backpacks for animals in the wild (see Colugo work with Greg Byrnes), and flexible microarrays to record from multiple muscles in insects. With the advent of miniature sensors, microcontrollers, GPS tracking, and machine vision techniques, we are entering a golden age for integrative biology.

  • Leveraging elastic instabilities for amplified performance: Spine-inspired high-speed and high-force soft robots. Science Advances. 8 May 2020. Yichao Tang, Yinding Chi, Jiefeng Sun, Tzu-Hao Huang, Omid H. Maghsoudi, Andrew Spence, Jianguo Zhao, Hao Su, Jie Yin
  • Infrared videography of a subcutaneous knee tattoo as a simple and inexpensive method to overcome skin motion artifact in rodent kinematics. BioRXiv. Available soon after Aug 22nd, 2022. George Moukarzel, Bradley C. Rauscher, Chetan A. Patil, Andrew J. Spence.
  • A versatile system for neuromuscular stimulation and recording in the mouse model using a lightweight magnetically coupled headmount.Journal of Neuroscience Methods 1 October 2021. Annie Vahedipour, Matthew R.Short, Azadeh Timnak, Omid Haji Maghsoudi, Thomas Hallowell, Jonathan Gerstenhaber, Ornella Cappellari, Michel Lemay, Andrew J.Spence.
  • A MATLAB application for automated H-Reflex measurements and analyses.Biomedical Signal Processing and Control. Volume 66, April 2021. George Moukarzel, Michel A. Lemay, Andrew J.Spence.
  • Addition of angled rungs to the horizontal ladder walking task for more sensitive probing of sensorimotor changes.PLOS One. 5 February 2021. Jaclyn T. Eisdorfer, Michael A. Phelan, Kathleen M. Keefe, Morgan M. Rollins, Thomas J. Campion III, Kaitlyn M. Rauscher, Hannah Sobotka-Briner, Mollie Senior, Gabrielle Gordon, George M. Smith, Andrew J. Spence.
  • A novel method for robust markerless tracking of rodent paws in 3D.URASIP Journal on Image and Video Processing. 14 September 2019. Omid Haji Maghsoudi, Annie Vahedipour, and Spence, A. J.
  • 3D Based Landmark Tracker Employing a Superpixels Method for Neuroscience, Biomechanics, and Biology Studies.International Journal of Imaging Systems and Technology Online Early. 12 March 2019. Haji Maghsoudi, O., Vahedipour, A. and Spence, A.
  • Open-source Python software for analysis of 3D kinematics from quadrupedal animals.Biomedical Signal Processing and Control 51, pp 364-373. 26 February 2019. Haji Maghsoudi, O., Vahedipour, A. and Hallowell, T., and Spence, A.
  • Matlab Software to Characterize Electrode Impedances for Neuroscience Applications.Journal of Neuroscience Methods 307, 1 September 2018, Pages 70-83. Haji Maghsoudi, O., Vahedipour, A., George, S. P., Hallowell, T., Robertson, B., Short, M., Gerstenhaber, J. and Spence, A.
  • Application of Superpixels to Segment Several Landmarks in Running Rodents.Journal of Pattern Recognition and Image Analysis (PRIA) 28:3 pp. 468-482, July 2018. Omid Maghsoudi, Annie Vahedipour, Ben Robertson, and Andrew Spence.
  • Superpixels Based Marker Tracking vs. Hue Thresholding In Rodent Biomechanics Application.51st Asilomar Conference on Signals, Systems and Computers. Pacific Grove, California, IEEE. October 29th, 2017. Omid Maghsoudi, Annie Vahedipour-Tabrizi, Ben Robertson and Andrew Spence.
  • A Rodent Paw Tracker Using Support Vector Machine.IEEE Signal Processing in Medicine and Biology Symposium (SPMB) (2016). Haji Maghsoudi, O., A. V. Tabrizi, B. Robertson, P. Shamble and A. Spence.
  • A Novel Automatic Method to Track the Body and Paws of Running Mice in High Speed Video.The IEEE Signal Processing in Medicine and Biology Symposium (2015) Maghsoudi, O., A. Vahedipour-Tabrizi, B.D. Robertson, P.D. Shamble, and A.J. Spence.
  • A.J. Spence, K.B. Neeves, D. Murphy, S. Sponberg, B.R. Land, R.R. Hoy, and M.S. Isaacson, Flexible multielectrodes can resolve multiple muscles in an insect appendage. (2007). Journal of Neuroscience Methods 159, p 116-124.
  • G. Byrnes, N. T-L. Lim, and A.J. Spence. Take-off and landing kinetics of free-ranging Malayan colugos (Galeopterus variegatus). Proceedings of the Royal Society B 275, no 1638, p. 1007-1013.
  • Accuracy of the TurfTrax Racing Data System for determination of speed and position.
    Equine Veterinary Journal, 40, (2008) 680-683.
    A.J. Spence, H. Tan & A.M. Wilson.
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    Terrestrial Locomotion

    running cockroach with backpack Energetics of Locomotion Primer
    How much energy does it cost to move?

    In this primer, we provide a birds-eye view of what costs energy when animals move, and the ways in which they minimize energy consumption. For terrestrial animals, this includes their selection of gaits as a function of speed.

  • The economy of terrestrial locomotion.
    Current Biology.Volume 32, Issue 12, 20 June 2022, Pages R676-R680.
    Andrew J. Spence, Simon D. Wilshin, Greg Byrnes.
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    gaits Gait Dynamics
    Gaits

    gaitspotWhen animals move they often choose a specific gait, or stereotyped pattern of movement, for a given speed. These include the familiar walk, trot, and gallop of horses. Postdoc Simon Wilshin, working with our collaborators Clark Haynes, Shai Revzen, and Dan Koditschek, has been spearheading some fascinating new work on animal gaits. We have developed new phase based approaches to quantifying gaits, on top of which we are developing a dynamical systems model of gait control. With these tools, we have been able to examine the role of static stability in shaping gait transitions in dogs, have found that dogs walking on natural rough terrain adjust their gait to be more "trot like," and are gearing up to use this model as a controller for our legged robot.

  • Longitudinal quasi-static stability predicts changes in dog gait on rough terrain. Journal of Experimental Biology (2017) (2017) 220 (10) 1864–1874. May 17th, 2017. Simon Wilshin, Michelle Reeve, G. Clark Haynes, Shai Revzen, Daniel Koditschek, and Andrew Spence.
  • Morphology and the gradient of a symmetric potential predicts gait transitions of dogs. Biological Cybernetics (2017) 111 (3) 269-277. August 2017. Simon Wilshin, G. Clark Haynes, Jack Porteous, Daniel Koditschek, Shai Revzen, and Andrew Spence.
  • Limping following limb loss increases locomotor stability. Journal of Experimental Biology 221: jeb174268, September 25th, 2018. Simon Wilshin, Paul Shamble, Kyle J. Hovey, Ryan Harris, Andrew J. Spence, and S. Tonia Hsieh.
  • Uncovering the structure of the mouse gait controller: mice respond to substrate perturbations with adaptations in gait on a continuum between trot and bound. Journal of Biomechanics 78 pp. 77-86. September 10th, 2018. Vahedipour, A., Haji-Maghsoudi, O., Wilshin, S., Shamble, P., Robertson, B. D. and Spence, A. J.
  • Dog galloping on rough terrain exhibits similar limb co-ordination patterns and gait variability to that on flat terrain. Bioinspiration & Biomimetics. Online Accepted Manuscript 21 August 2020. Wilshin, S., Reeve, Michelle A., and Spence, A.J.
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    running cockroach with backpack Control of legged locomotion on soft surfaces
    Control of legged locomotion on soft surfaces

    We know that legged animals, irrespective of size and leg number, have running mechanics that resemble a mass bouncing forward on a virtual leg spring. Further, we know that humans compensate for soft surfaces by stiffening this virtual leg. In this paper we showed that, surprisingly, insects do not compensate for the surface by adjusting their virtual leg stiffness. Instead we found that a simple, feedforward model actuated at the hip was sufficient to explain our results. This impacts future research into which aspects of locomotion the neural controller must handle, and could aid in designing active prosthetic limbs that are stable on compressible terrain.

    Technologically, this paper leveraged tools from physics and computer science to break new ground in biology. We measured the dynamics of the freely running insect with a MEMS accelerometer backpack fused to data from an automatic video tracking system. Not only does the backpack allow continuous recording of large amounts of data, a requirement to test many of the most exciting, dynamical systems based hypotheses of control, it enables real-time, phase locked perturbations.

    Currently, we are looking at whether dogs stiffen their virtual leg on soft surfaces, and seeking explanations for their behaviour with a six-legged robot, the X-RHex Lite (XRL), in collaboration with Prof. Dan Koditschek at the Univ. of Penn.


  • Spence, A.J., Revzen, S., Seipel, J., Mullens, C., and Full, R.J. (2010). Insects running on elastic surfaces. J. Exp. Biol. 213: 1907-1920
  • Spence, A.J. (2011). Control strategies for legged locomotion: a comparative approach. 7th European Nonlinear Dynamics Conference (ENOC), Rome, Italy.
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    max Maximum performance
    Maximum performance

    draftWhat limits maximum performance in legged locomotion? Can we apply different loads to moving animals to determine the constraints to speed? Many animals rely on speed to escape predators or catch prey, and some do so in groups. How does being in a pack of animals affect performance? In a 2009 Science paper, we studied the mechanics of race riding jockeys, and found that their crouched posture, which mechanically isolates them from the horse, makes it easier for the horse, causing a large drop in race times at the turn of the century. More recently, using a large data set from a wireless tracking system in place during actual horse races, we have found that aerodynamic drafting, or moving close behind another horse to reduce drag, has a significant effect on race times. PhD student Zoe Self has done further nice work with these data, showing that horses slow down far more than expected when going downhill, suggesting a mechanical, or force limit, to their performance.

  • Ground Reaction Forces Of Overground Galloping In Ridden Thoroughbred Racehorses.Journal of Experimental Biology. 23 August 2019. Self-Davies, Z.T., Spence, A.J., Wilson, A.M.
  • External Mechanical Work in the Galloping Race Horse. Biology Letters. 20 February 2019. Self, Z.T., Spence, A.J., Wilson, A.M.
  • Not just great TV -- broad insights from extreme animal performance.Current Biology Magazine 28:20. 22 October 2018, Pages R1176-R1177. Spence, A. J.
  • Fast horses, robots, and neurotechnologies: Discovering how to go fast on legs.Science in Parliament (2013) 70 (3): 23–25. Summer 2013 Issue. A.J. Spence.
  • Andrew Spence, Andrew Thurman, Michael Maher, and Alan Wilson. (2012). Speed, pacing strategy and aerodynamic drafting in Thoroughbred horse racing. Biology Letters. Online ahead of print.
  • T. Pfau, A.J. Spence, S. Starke, M. Ferrari, and A.M. Wilson. (2009). Modern Riding Style Improves Horse Racing Times.Science 325 p. 289.
  • Racehorse speed supports a power constraint to incline running and a force constraint to decline running.Journal of Applied Physiology (2012) Zoe Self, Andrew Spence, & Alan Wilson.
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    degu Neuromuscular control of legged locomotion
    Neuromuscular control of legged locomotion

    controlHow legged animals move fast is still an intriguing puzzle. We know what parts of the animal contribute to it: muscles, skeleton, sense organs, the nervous system. But we don't know how much of fast locomotion is handled by the musculoskeletal system, and how much is actively controlled by the nervous system. Muscles are complicated, non-linear actuators, that may be able to handle a broad range of perturbations with the same input signal. Sensory feedback from limbs may be too delayed during fast locomotion to be useful, and therefore be ignored. PhD student Anna Liedtke has been working to understand whether large animals, in this case horses, can make use of sensory feedback from the distal limb during trotting on a treadmill. So far, anesthetizing the hoof does not appear to affect the kinematics of horse locomotion: suggesting that this feedback is not necessary for steady state trotting in horses. With Simon Sponberg, we examined the potential of muscles to control the body of cockroaches: we found that injecting spikes into a main extensor muscle of freely running cockroaches had surprisingly little effect on their body dynamics: this highlighted to context dependence of neural commands.

  • Liedtke, A.M., Moore, S., Witte, T., Spence, A.J. (2012). How do animals with limited distal limb musculature use sensory feedback during locomotion? SICB 2012 Charleston 79.2
  • Simon Sponberg, Andrew J. Spence, Chris H. Mullens, Robert J. Full. (2011). A single muscle's multifunctional control potential of body dynamics for postural control and running Phil. Trans. Roy. Soc. B 366, no. 1570 p. 1592-1605.
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    scaling Scaling
    Scaling

    scalingfigEvolution as carried out experiments for us, producing animals of a huge range of size. Not only that, but animals have adapted diverse locomotor behaviours. This presents us with an opportunity: because the physics of the world changes with size, we can use size as a "knob" to look for systematic changes in how animals work. With size as a control parameter, we can try to see if, for example, there are consistent differences in how small animals like insects, versus larger animals like dogs and horses, control their bodies as they move. In a 2009 Primer, I offer an introduction to analysis of scale in biology, and highlight some fertile ground for future analyses of scaling. In an editorial with John Hutchinson, we highlight the growing opportunities to link across length scales in analyses of size, and how size is controlled.

  • Spence, A.J. and Hutchinson, J.R. (2012). A Growing Size Synthesis. Current Biology 22 R309-R314.
  • Spence, A.J. (2009). Scaling in biology Current Biology 19, R57-R61.
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    Gliding

    Biomechanics and evolution of gliding in mammals
    Biomechanics and evolution of gliding in mammals

    draftSome animals have evolved spectacular locomotor adaptations to their ecological niche. Colugos are large, nocturnal primates that live in the rainforests of Singapore. Weighing a kilogram, they glide many tens of meters through the canopy at night. In a long term collaboration with Greg Byrnes, we have studied the biomechanics and evolution of colugos, in order to understand the evolutionary pressures that have shaped this extraordinary behaviour, and to identify the key mechanisms that support gliding behaviour. Using novel accelerometer backpacks specifically designed for these animals, we discovered that colugos are quite aerobatic; they use a parachute maneuver to reduce forces on landing. Placed in a evolutionary context, we further found that gliding is significantly correlated with a shift in diet: particularly to one consistenting of relatively low quality neutrients, that are sparsely located. Interestingly, we did not find support for the hypothesis that gliding evolved as an energetically cheap form of locomotin.

  • Greg Byrnes, Thomas Libby, Norman, T.-L. Lim, and A.J. Spence. (2011). Gliding saves time but not energy in Malayan Colugos. Journal of Experimental Biology 214 p2690-2696.
  • Greg Byrnes and A. J. Spence. (2011). Ecological and biomechanical insights into the evolution of gliding in mammals Integrative and Comparative Biology 51(6): 991-1001.
  • G. Byrnes, N. T-L. Lim, C. Yeong, and A.J. Spence. Sex differences in the locomotor behavior and ecology of a gliding mammal ( Galeopterus variegatus) determined from animal-borne inertial sensors. (2011) Journal of Mammology 92 no. 2, p444-451.
  • G. Byrnes, N. T-L. Lim, and A.J. Spence. Take-off and landing kinetics of free-ranging Malayan colugos (Galeopterus variegatus). Proceedings of the Royal Society B 275, no 1638, p. 1007-1013.
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