Physiology Brownbag Seminars – Spring 2018

Physiology Brownbag Seminars – Spring 2018

Physiology “brown-bag” lunchtime seminars are held twice a month on WEDNESDAYS at noon in Applied Physiology Building, room 1253 (or as indicated). Special seminar dates/times outside of the regular schedule are indicated as such.

Contact Dr. Boris Prilutsky, boris.prilutsky@biosci.gatech.edu, to be considered as a future speaker, added to the e-mail distribution list, if you would like to meet with a speaker, or for other seminar-related inquiries.
For directions: Applied Physiology

SEMINAR: Wednesday, January 24, 2018

New players and concepts in skeletal biomechanics

Elazar Zelzer, PhD
Department of Molecular Genetics
Weizmann Institute of Science

Abstract

The main focus of my lab is on regulatory interactions among different tissues, including bone and cartilage, muscle and tendon and neuronal tissues, during the development and function of the musculoskeletal system.

  BIO: Elazar Zelzer completed his bachelor’s and master’s degrees at Ben-Gurion University of the Negev in Israel, and went on to receive his Ph.D. in 1999 in molecular genetics from the Weizmann Institute of Science. He then worked as a postdoctoral fellow in Professor Bjorn Olsen’s lab at Harvard Medical School from 1999 to 2004, during which he studied bone development. He returned to the Weizmann Institute of Science in Israel in 2004, where he was appointed Senior Scientist in the Department of Molecular Genetics. His research group’s interest lies in skeletogenesis, and they focus specifically on two different aspects of skeletal development using advanced murine research techniques; the first, looking at the development of the musculoskeletal system, and the second, at the complex interactions between the developing skeleton and the vasculature.

Host: Timothy C. Cope, PhD
Time: 12:00 – 1:00 PM
Location: Applied Physiology Building, Room 1253

SEMINAR: Wednesday, February 7, 2018

Minimal evidence for a secondary loss of strength after skeletal muscle injury but NSAIDs seem to work anyhow

Gordon Warren, PhD
Department of Physical Therapy
Georgia State University

Abstract

In most types of skeletal muscle injury, there is an immediate loss of strength after the injury is induced. However, there has been debate as to where a secondary, additional strength loss occurs as a result of inflammation spilling over onto initially undamaged tissue (a.k.a. bystander injury). This talk will present strong evidence that a secondary injury does not occur, at least not one that results in a strength loss. However, this talk will also provide strong evidence that non-steroidal anti-inflammatory drugs (NSAIDs) improve the recovery of strength after injury, presumably by their effects on inflammatory processes. An attempt to explain the apparent disconnect between the two observations will be done by discussing the spatial and temporal heterogeneity of injury and recovery processes.

  BIO: Dr. Gordon Warren is a Distinguished University Professor in the Department of Physical Therapy at Georgia State University. He has a B.S. in nuclear engineering from Georgia Tech and a M.S. in biomedical engineering from MIT. His Ph.D. was in exercise physiology from UGA. He has conducted research on skeletal muscle injury and combined muscle-bone injuries for 27 years. He has conducted this research using both human and animal models. In his animal research, he has implemented single fiber models as well as in vitro, in situ, and in vivo muscle models in the induction of muscle injury as well as in the assessment of the muscle’s functional capacities. His research has focused on explaining the mechanisms of strength loss after injury and the recovery therefrom.

Host: Boris I. Prilutsky, PhD
Time: 12:00 – 1:00 PM
Location: Applied Physiology Building, Room 1253

SEMINAR: Wednesday, February 21, 2018

Title: Organization of Golgi tendon organ feedback in the lower limb: functional inferences

Mark Lyle, PT, PhD
Division of Physical Therapy
Emory University School of Medicine

Abstract

Proprioceptive feedback from muscle spindles and Golgi tendon organs are known to influence motor coordination during locomotor tasks. The coordinating influences from proprioceptive feedback are made possible by the extensive neural projections in the spinal cord that connect lower limb muscles. In this talk, I will highlight work over the last several years examining the strength and distribution of Golgi tendon organ feedback between lower limb muscles, and the growing evidence that this network could function as neural linkages that help regulate whole-limb mechanics.

Mark Lyle BIO: Dr. Mark Lyle is an Assistant Professor in the Division of Physical Therapy at Emory University School of Medicine. He has a B.S. in Zoology (Neuroscience Minor) from Miami University, Oxford, OH, an M.S. in Physical Therapy from Simmons College, Boston, MA and a Ph.D. in Biokinesiology from University of Southern California, Los Angeles. He did his postdoctoral research in Neurophysiology at Georgia Institute of Technology. His research focus over the last 10 years has been to identify governing neural control principles that enable normal and underlie impaired task dependent lower limb control with an emphasis on clarifying the functional role of proprioceptive feedback (i.e. muscle spindles and Golgi tendon organs). His lab is particularly interested in determining how and to what extent proprioceptive feedback is modulated to meet unique task demands, and the extent to which the adaptive capacity to modulate proprioceptive feedback is influenced by injuries, aging and rehabilitation strategies (e.g. motor practice, targeted neuromodulation).

Host: Boris I. Prilutsky, PhD
Time: 12:00 – 1:00 PM
Location: Applied Physiology Building, Room 1253

 

SEMINAR: Wednesday, March 7, 2018

Title: Neuronal activity, neurotrophins, and axon regeneration in peripheral nerves

Arthur W. English, PhD
Department of Cell Biology
Emory University School of Medicine

Abstract

Traumatic injuries to peripheral nerves are common and recovery from them is rare. No non-surgical treatments exist. Exercise applied following nerve injuries has been shown to enhance axon regeneration, but exercise cannot be applied to many nerve injuries, so the basis for its effectiveness is of interest. One hypothesis is that an increase in neuronal activity during exercise that promotes enhanced axon regeneration. This was tested using optogenetics. Optical activation of both motor and sensory neurons resulted in enhanced regeneration. Optical inhibition of motoneurons during exercise blocked its effect on axon regeneration. Subthreshold activation of motoneurons using excitatory Designer Receptors Exclusively Activated by Designer Drugs (DREADDs) also stimulated axon regeneration. Using selective knockout mice, neuronal BDNF-trkB signaling was shown to be required for the effects of exercise on axon regeneration in peripheral nerves. Similar augmentation can be achieved using treatments with small molecule trkB agonists. Manipulation of downstream effects of this neurotrophin, and perhaps other activity-stimulated growth factors, on the stabilization of nascent microtubules in regenerating axons has a particularly potent effect on regeneration.

Photo of Arthur W. English BIO: Dr. Arthur W. English is a Professor of Cell Biology, Associate Professor of Rehabilitation Medicine, Affiliate Scientist, Yerkes Regional Primate Research Center at Emory University. He received his Ph.D. in Neuroscience, at the University of Illinois in 1974. The main interest in his laboratory is enhancing functional recovery following injury to the peripheral nervous system. Peripheral nerve injuries are common clinically but functional recovery from them is rare. Following nerve injury, denervated muscles are deprived of neural control and sensory feedback regulating muscle function is lost. In addition, synaptic inputs onto spinal motoneurons are withdrawn. The slow growth of regenerating axons and the slow reformation of synapses, both in the periphery and in the CNS, are the reasons given for poor functional outcomes.

 

Host: Boris I. Prilutsky, PhD
Time: 12:00 – 1:00 PM
Location: Applied Physiology Building, Room 1253

 

SEMINAR: Wednesday, March 28, 2018

Title: Do the springs in your muscles put a bounce in your step?

Thomas Roberts, PhD
Department of Ecology and Evolutionary Biology
Brown University

Abstract

Elastic structures within muscles have the potential to store and recover energy during movement, potentially enhancing muscle performance.  Intramuscular elasticity is often modelled (e.g., in Hill-type models) as a spring element parallel to the contractile element. Such arrangement implies that intramuscular springs are engaged only at long muscle lengths, and only when fibers are lengthened, predictions that are generally supported by measurements of passive muscle stiffness. Because most studies suggest that muscles operate at relatively short lengths during locomotion, and often do not lengthen, the role of intramuscular elasticity has generally been assumed to be limited. Recent work in our lab has focused on an alternative construction of a Hill-type model that includes the deformation of muscles in three dimensions. Model and experimental data predict that in pennate muscles, intramuscular springs will cycle elastic strain energy in virtually all contractions, regardless of fiber length or length trajectory, due to deformation of the muscle off-axis to the fiber line of action. We hypothesize that the collagenous extracellular matrix of muscles acts as a spring to perform functions that have previously been assigned only to in-series tendons, including the cycling of elastic energy during running, and the amplification of muscle power output during jumping.

  BIO: Tom Roberts is a professor in the department of Ecology and Evolutionary Biology at Brown University. As a comparative biomechanist, he exploits animal diversity to investigate the link between muscle function and movement. A particular focus of his work has been the central role that elastic mechanisms play in a wide range of movements, in particular how tendon elasticity interacts with the contractile properties of muscle to influence the energetics and mechanics of locomotion. Recent work in his lab focuses on the role that elastic structures within muscle, such as the collagenous extracellular matrix, store and recover energy associated with muscle shaped changes that occur during contractions.

Host: Greg Sawicki, PhD
Time: 12:00 – 1:00 PM
Location: Applied Physiology Building, Room 1253

 

SEMINAR: Wednesday, April 4, 2018

Title: Network mechanisms underlying stable motor actions

William Liberti, PhD
Department of Electrical Engineering & Computer Science
University of California, Berkeley

Abstract

Precise motor skills are acquired and maintained through practice; a process of exploratory trial-and-error learning where evaluation mechanisms can differentially reinforce network patterns that produce more desired outcomes and weaken or punish patterns of activity that produce worse outcomes. However, the neural underpinnings of how practice may evaluate, maintain and sharpen the stereotypy of a precise motor action are not well understood. The zebra finch songbird offers a chance to explore the mechanisms of motor maintenance in a  particularly well defined setting: song is a constrained behavior that naturally converges around a set point, and is actively maintained and stabilized in light of external feedback and environmental challenges. While song is primarily a courtship ritual to attract females, finches will also sing in isolation, otherwise known as ‘undirected’ song,  and these songs have comparatively lower stereotypy.  Undirected song could serve as an opportunity for premotor networks to explore potentially better configurations to optimize motor output, since the performance outcome is less critical. We developed custom carbon fiber microelectrodes, cell-type specific genetic tools, and ultra-light head-mounted miniscopes to investigate the mechanistic basis of long-term motor stability of the premotor area HVC. We find that during undirected practice, some neurons are active more probabilistically, and less robustly, and trial to trial variability is not highly correlated across cells. In contrast, when song is directed to a female, this exploration is largely diminished.  In addition, while the timing of projection neurons is extremely stereotyped and precise within a day, neurons can ‘dropout’ and new neurons can ‘drop-in’  across days-  largely over intervals of sleep. In spite of these shifts at the single neuron level, local ensembles and inhibitory interneurons produce reliable patterns of activity over month-long timescales. These observations suggest that state-dependent variations could contribute to the long-term stability of the motor network, and that stereotyped motor skills can be supported by stable ensemble dynamics that persist in spite of single neuron instability.

 

Host: T. Richard Nichols, PhD
Time: 12:00 – 1:00 PM
Location: Applied Physiology Building, Room 1253

 

SEMINAR: Wednesday, April 18, 2018

Title: Effort Minimization: A General Principle of Legged Locomotion?

Jonas Rubenson, PhD
College of Health and Human Development
Pennsylvania State University

Abstract

The nervous system has numerous objectives during locomotion.  Studies of humans and other animals suggest that energy (effort) minimization may be one of the primary objectives during steady-speed walking and running.  The importance of effort minimization is, however, likely context-dependent. In this talk I will provide brief snapshots into a series of studies exploring effort minimization during legged locomotion including: 1) the generality of locomotor energetic optimization across bipedal species; 2) optimization of muscle efficiency; 3) effort minimization in human gait transitions; 4) developmental plasticity of locomotor energetics; and 5) recent human gait experiments aimed at teasing out the relative importance of energy vs. stability optimization and global (organismal) vs. local (muscle) effort.  These topics are intended as a background to discuss and debate the question of effort minimization as a design principal in legged locomotion (and more broadly, animal motor coordination).

 BIO: Dr. Rubenson is an Associate Professor in the Biomechanics Laboratory (Department of Kinesiology) and directs the Muscle Function + Locomotion Lab, Penn State University. Rubenson’s work is dedicated to understanding the biomechanics and energetics of legged locomotion.  His group is interested in mechanisms of locomotor adaptation and optimization, and, in particular, the biomechanical determinants of locomotor energy cost. Rubenson’s work primarily focuses on basic research both in humans and using a comparative approach, and more recently includes clinical- and pre-clinical studies.

Host: Greg Sawicki, PhD
Time: 12:00 – 1:00 PM
Location: Applied Physiology Building, Room 1253

 

SEMINAR: Wednesday, April 25, 2018

Title: Reverse engineering of firing patterns of human motoneurons to identify the synaptic organization of motor commands

Charles J. Heckman, PhD
Physiology, Physical Medicine and Rehabilitation
Physical Therapy and Human Movement Sciences

Northwestern University Feinberg School of Medicine

Abstract

Motoneurons are unique in being the only neurons in the CNS whose firing patterns can be easily recorded in humans, but only recently has it become possible to simultaneously record the firing patterns of many motoneurons via array electrodes placed on the skin.  These population firing patterns contain detailed information about the synaptic organization of motor commands.  It is now well established that motor commands consist of three components, excitation, inhibition and neuromodulation;  the importance of the third component had become increasingly evident. Firing parameters linked to each of these three components will be considered, along with discussion of their limitations.  Our recent efforts to develop a quantitative “reverse engineering” approach to estimate both the amplitudes and temporal patterns of inputs to motoneurons will also be presented. Taken together, these analyses have the potential to transform our understanding of the structure of human motor commands in both normal and pathological states.

 BIO: Dr. Heckman’s lab has worked on the mechanisms of spinal motor output for over 25 years. Motoneurons provide the output to muscle for all movements and his systematic studies of these cells provide a fundamental underpinning for understanding motor function and its rehabilitation. The techniques in his lab span the cellular, circuit and system levels in animal preparations and the resulting data has allowed him to achieve remarkably deep insights in motor function in human subjects. His development of biologically realistic computer simulations of motoneurons synthesizes this multi-level information and provides both predictions to guide experiments in humans and a deeper understanding of cellular mechanisms of human function, with an emphasis on developing new therapies for spinal injury, ALS and cerebral stroke.

Host: Tim Cope, PhD
Time: 12:00 – 1:00 PM
Location: Applied Physiology Building, Room 1253

SEMINAR: Friday, May 18, 2018

Title: Adaptation and balance in people with locomotor deficits

Brian Selgrade , PhD
Department of Biomedical Engineering
University of North Carolina, Chapel Hill

 BIO: Dr. Selgrade’s  research focuses on biomechanics, motor learning, and adaptation to mechanical perturbations and visual feedback. He is particularly interested in how changes to the environment during locomotion affect balance in healthy and clinical populations

Host: Young-Hui Chang, PhD
Time: 12:00 – 1:00 PM
Location: Applied Physiology Building, Room 1253