Physiology Brownbag Seminars – Fall 2017

Physiology Brownbag Seminars – Fall 2017

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, September 20, 2017

Using ultrasound imaging to understand dynamic muscle-tendon behaviour: experimental and modelling approaches

Taylor Dick, PhD
School of Biomedical Sciences, University of Queensland, Australia
Department of Mechanical Engineering, Georgia Tech

Abstract

Skeletal muscle is the engine that produces force to power movement in humans and animals alike. To date the invasive nature of obtaining muscle-tendon forces in humans has limited our understanding of muscle function and restricted our ability to develop effective treatment protocols for diseased populations. Phenomenological, Hill-type models of are often used to predict muscle force, for example within musculoskeletal simulations of human movement. However, few studies have examined the accuracy of forces obtained from such models during in vivo motor tasks. The goal of my work is to develop, test, and refine methods to better quantify muscle mechanical output in humans, using ultrasound and electromyographic recordings, together with advanced Hill-type models. In this seminar I will first discuss imaging techniques to non-invasively estimate in vivo muscle-tendon forces.  Next, I will present a series of comparisons between ultrasound-based force estimates and predictions from traditional Hill-type models as well as from new-age models that account for task-dependent changes in motor unit recruitment or alterations in 3-dimensional muscle shape. These studies are helping to identify the contractile and architectural features of muscle models that are most critical for predicting time-varying patterns of force during dynamic muscle contractions in healthy and clinical populations. Finally, I will share new insights into how we are using ultrasound imaging to look ‘under the skin’ during tasks where muscle-tendon behaviour is challenging to predict—for example, during exoskeleton-assisted walking or during recovery from a fall.

  BIO: Dr Taylor Dick is a Lecturer in the School of Biomedical Sciences at the University of Queensland, Australia. She completed her PhD in 2016 at Simon Fraser University, Canada under the supervision of Dr James Wakeling. Following this, she conducted a Post-Doc in the PoWeR Lab within the Joint Department of Biomedical Engineering at North Carolina State University- University of North Carolina at Chapel Hill. Her researc focuses on using novel experimental and modelling tools to study muscle-tendon mechanics, to determine how neuromuscular properties are altered with age or disease, and to unveil how these disruptions affect muscle force production and locomotor performance.

 

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

 

SEMINAR: Wednesday, September 27, 2017

Muscles Stretch: factors that influence the active lengthening of skeletal muscles

Emily Abbott, PhD
Department of Mechanical Engineering
Georgia Tech

Abstract

Terrestrial vertebrates pounce on prey, negotiate uneven terrain, and ultimately come to a complete stop. To perform these controlled decelerations, an animal must absorb, or dissipate, mechanical energy in its skeletal muscles. This is achieved by eccentric contractions in which skeletal muscles actively produce force during an imposed stretch. My dissertation research investigated how timing of activation, relaxation rate and muscle architecture influence the rate of active lengthening of skeletal muscle.

  BIO: I am a recent PhD graduate from Dr. Azizi’s comparative biomechanics lab at UC Irvine. I am excited to join the lab of Dr. Sawicki as a postdoctoral scholar and collaborate with the Georgia Tech community. Here, I plan to continue to investigate physiological principles that underpin locomotion.

 

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

 

SEMINAR: Wednesday October 4, 2017

The effect of motor lateralization on bimanual coordination

Andrzej Przybyla, PhD
Department of Physical Therapy
University of North Georgia

Abstract

Bimanual coordination has been studied extensively for decades and the vast majority of work has been reporting a strong coupling between the two arms following the proposition by Kelso et al. (1979) who hypothesized that a single ‘super-ordinate’ controller is recruited during bilateral tasks. Given evidence of hemispheric lateralization of motor control and resulting significant interlimb differences in intralimb coordination (Sainburg et al., Dynamic Dominance Hypthesis), it is interesting to further our understanding of interplay between these two mechanisms of neural control of movement. Does a single ‘super-ordinate’ controller take over during bimanual coordination changing intralimb coordination of one or both arms? During this talk, I will present evidence suggesting individual control of each arm during bimanual coordination, i.e. no coupling. Namely, interlimb differences do persist in bimanual movements coordination and each limb cooperates in compensating task errors, thus stabilizing task performance, i.e. synergy. Furthermore, these synergies can be modified fairly rapidly, even in mild stroke patients whose bimanual coordination also reveals evidence that predictive mechanisms of bimanual coordination depend on the left hemisphere, consistently with Dynamic Dominance Hypothesis.

  BIO: Dr. Andrzej Przybyla (Dre) is a new Associate Professor in the Department of Physical Therapy at the University of North Georgia. He completed his PhD and the first postdoctoral experience in spine biomechanics at the University of Bristol, U.K. (2000-06), under the supervision of Drs. Michael Adams and Patricia Dolan. Following this, he joined Dr. Robert Sainburg’s laboratory at the Penn State University (2006-15) focusing his research on hemispheric lateralization of motor functions, i.e. bimanual coordination, motor decisions, stroke rehabilitation. He spent one year (2015-16) in the School of Sports and Exercises Sciences at the Liverpool John Moores University, U.K., working on clinical gait biomechanics and motor behavior. His research focuses on neural mechanisms of movement control and motor decision making with strong emphasis in applications to motor adaptation and learning, i.e. physical therapy, athletic training, aging.

 

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

 

SEMINAR: Wednesday, October 18, 2017

Performance stability in tasks performed by two persons

Stanislaw Solnik, PhD, PT
Department of Physical Therapy
University of North Georgia

Abstract

People frequently coordinate their motor behavior in daily life, and stability of this joint motor performance is crucial for successful implementation of many tasks (e.g., passing a glass of water, care-giver interactions with patients, etc.). When a person executes a task alone, the central nervous system coordinates redundant sets of elements to stabilize task performance. However, when two persons share a task, their nervous systems can only interact via sensory feedback. Thus, it is unclear whether similar coordination strategy may be facilitated in these situations. I will discuss recent projects exploring performance–stabilizing synergies in motor tasks involving two actors, including accurate multi-finger force production and prehension tasks.

  BIO: Throughout his academic career, Dr. Solnik conducted multidisciplinary research spanning the broad spectrum of movement science, including biomechanics, motor control and neuroscience. Dr. Solnik’s research exemplifies his commitment to the interdisciplinary and collaborative study of human movement, that justifies and provides evidence to clinical practice. He pursued research that helps to direct more focused and efficient interventions, ultimately advancing the practice of physical therapy. He received his pre and postdoctoral training in numerous research institutions including University of Southern California, East Carolina University, and Pennsylvania State University. Currently, Dr. Solnik is leading the research agenda of the Physical Therapy Department as director of research. He accepted an assistant professor position in the Physical Therapy Department in 2016.

 

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

SEMINAR: Friday, October 27, 2017

Learning to use a prosthetic device: Can serious games help?

Raoul M. Bongers, PhD
Center for Human Movement Sciences, University Medical Center Groningen
University of Groningen
The Netherlands

Abstract

Describing kinematics of grasping objects with a prosthesis and showing that this is less fluent than grasping with
an anatomical hand is taken as a starting point to focus on learning to improve rehabilitation of the use of upper
extremity prostheses. It will be argued that serious games have benefits for rehabilitation, and a main question
addressed in the presentation is on the requirements of serious games for prosthetic rehabilitation. Results will
be described of experiments on hand opening and closing control in 1-DOF prosthesis hands as well as the
producing of triggers to switch between grip types in multi-DOF prosthesis hands and how these can be trained
with serious games. It will be argued that a task specific approach, inspired from Ecological Psychology, is
required when developing serious games for prosthesis use. Finally, it will be shown how different types of
feedback in conventional training as well as training with a game affect the learning of the producing of grip types
in multi-DOF prostheses controlled with pattern recognition. In the conclusions recommendations with regard
to developing serious games for prosthesis use will be provided that is inspired from a combined approach of
Ecological Psychology and Dynamical Systems Account to motor coordination.

For those who want to meet with Dr. Bongers, please contact Lewis Wheaton (law@gatech.edu). He will
have availability on Friday morning.

Host: Lewis A. Wheaton, PhD
Time: 12:00 – 1:00 PM
Location: Applied Physiology Building, Room 1253

 

SEMINAR: Wednesday, November 1, 2017

Distribution of TTX-sensitive voltage-gated sodium channels in primary sensory endings of mammalian muscle spindles

Dario I. Carrasco, PhD
School of Biological Sciences
Georgia Tech

Abstract

Knowledge of the molecular mechanisms underlying signaling of mechanical stimuli by muscle spindles remains incomplete.  In particular, the ionic conductances that sustain tonic firing during static muscle stretch are unknown.  We hypothesized that tonic firing by spindle afferents depends on sodium persistent inward current (INaP), and we tested for the necessary presence of the appropriate voltage-gated sodium (NaV) channels in primary sensory endings.  We began study of the NaV1.6 isoform, selected both for its capacity to produce INaP and for its presence in other mechanosensors that fire tonically.  We found NaV1.6 immunoreactivity (IR) concentrated in heminodes, where tonic firing is presumably generated, and we were surprised to find NaV1.6 IR strongly expressed also in the sensory terminals where mechano-transduction occurs.  We established consistency in this spatial pattern of NaV1.6 IR distribution for three mammalian species (rat, cat, and mouse) and went on to verify that primary spindle afferents in all three species fire tonically.  These findings meet some of the conditions needed to establish participation of INaP in tonic firing by primary sensory endings.  We extended study to two additional NaV isoforms, selected for their sensitivity to tetrodoxin (TTX), excluding TTX resistant NaV channels, which alone are insufficient to support firing by primary spindle endings.  Positive immunoreactivity was found for NaV1.1, predominantly in sensory terminals together with NaV1.6, and for NaV1.7 mainly in pre-terminal axons.  Differential distribution in primary sensory endings suggests specialized roles for these three NaV isoforms in the process of mechanosensory signaling by muscle spindles.

BIO:  Dr. Dario Carrasco is a Research Scientist in the School of Biological Science at Georgia Tech.  He completed his PhD in Exercise Physiology at the University of Georgia (1993-1996).  Immediately after, he conducted a Post-Doc in Dr. Arthur English’s laboratory in the Department of Cell Biology at Emory University (1996-2003) where he studied the contribution of neuromuscular compartments to joint biomechanics and later, under an NRSA fellowship, studied the influence of Neurotrophin on the development of skeletal muscle fiber phenotype.  He later joined Dr. Marty Pinter’s laboratory in the Department of Physiology at Emory University where he focused his research on motor neuron disease (2003-2015).  He joined Dr. Timothy Cope’s laboratory at Georgia Tech in 2015. Currently, the main focus of his research is to understand the molecular mechanisms underlying the changes in neuronal excitability observed in sensory and motor neurons after trauma, disease, and chemotherapy-induced injury.

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

 

SEMINAR: Wednesday, November 22, 2017

Multimodal Processing in the Central Vestibular System: Vestibular and Somatosensory Inputs

Andrew A. McCall, PhD
Department of Otolaryngology
University of Pittsburgh

Abstract

Balance control is inherently multimodal: the central nervous system receives afferent inputs from multiple sensory systems, including the vestibular, visual, and somatosensory systems, and processes these sensory inputs to adjust motor outflow for maintenance of balance.  Dysfunction of any of these inputs can lead to sensory ambiguity and increased postural instability and risk of fall.  Improved understanding of the neural underpinnings of balance control should lead to novel therapeutic targets for patients suffering from sensory dysfunction disorders leading to imbalance.  The focus of this talk will be on the processing of somatosensory and vestibular information within the central nervous system, with a particular focus on limb somatosensory inputs to vestibular processing centers in the brainstem.

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