Physiology Brownbag Seminars – Fall 2021

Physiology “brown-bag” lunchtime seminars are normally held 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. In Fall 2021, speakers will present their talks in person or remotely. All talks will be broadcast via BlueJeans.

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, August 25, 2021

Flexibility, Robustness, and Multifunctionality of Bursting Patterns of Half-Center Oscillators

Gennady S. Cymbalyuk, PhD
Neuroscience Institute and Department of Physics and Astronomy
Georgia State University

Abstract

Specialized oscillatory neuronal circuits, central pattern generators (CPGs), control rhythmic movements in a flexible yet robust fashion to adjust to changes of environment and behavioral goals.  We investigate dynamics of bursting patterns produced by models of Half-Center Oscillators (HCOs). HCO is a ubiquitous motif of CPGs, where two neurons or two neuronal populations are connected in a mutually inhibitory manner. We show that HCOs are capable of producing a wide variety of rhythmic patterns on different time scales. In the medicinal leech, a HCO model explains how co-modulation of ionic currents provides flexibility and robustness to a CPG controlling heart beat with a period of 8 s. With similar HCO models we describe mechanisms of multifunctional CPGs. One model describes how an isolated neonatal rodent spinal cord preparation could exhibit continuous locomotor bursting rhythms (period ~1 s) and a complex pattern evoked by dopamine: a very slow episodic bursting rhythm (period ~50 s), in which episodes of the fast-bursting rhythm are interrupted by long pauses. Another model describes how an HCO circuit representing a cat’s CPG could produce continuous locomotor bursting rhythms (period ~1 s) and a transient paw shake response (period ~0.1 s). We discuss possible roles of interactions of membrane ionic currents, like the Na+/K+ pump and hyperpolarization-activated currents in the cases of the leech heartbeat HCO and rodent spinal HCO.

Bio: Dr. Gennady S. Cymbalyuk is an Associate Professor and the Head of the Dynamical Neuroscience Laboratory at the Neuroscience Institute of Georgia State University. He received his Ph.D. degree in Physics and Mathematics from the Physics Department at Moscow State University and the Institute of Mathematical Problems in Biology of Russian Academy of Sciences in 1996. The topic of his thesis was “Modeling of movement coordination during locomotion on the basis of synchronization of oscillators.” His Ph.D. adviser was professor Roman Borisyuk. Dr. Cymbalyuk did his postdoctoral work in the laboratory of professor Ronald L. Calabrese in the Biology Department at Emory University in 1998-2003. He studied the leech heartbeat central pattern generation. Dr. Cymbalyuk joined the Department of Physics and Astronomy at Georgia State University in 2004. His current research interests are experimental and theoretical analysis of oscillatory neuronal circuits.

Host: Boris I. Prilutsky, PhD
Time: 12:00 – 1:00 PM
Location: Applied Physiology Building (555 14th Street NW, 30318), Room 1253

BlueJeans Link

SEMINAR: Wednesday, October 20, 2021

Spinal locomotor networks activated by supraspinal commands and by epidural stimulation of the spinal cord in cats

Pavel V. Zelenin, PhD
Department of Neuroscience
Karolinska Institute

Abstract

Locomotion is a vital motor function for both animals and humans. The basic neuronal networks controlling forward locomotion are located at the spinal–brainstem–cerebellum level. The basic pattern for locomotor movements is generated by spinal neuronal networks. These networks are activated by supraspinal commands caused by activation of brainstem command centers (e.g., mesencephalic locomotor region, MLR). Injuries to the descending pathways prevents such activation resulting in lost/impaired locomotor function. Epidural electrical stimulation (ES) of the spinal cord can restore/improve locomotor movements in patients. However, operation of locomotor networks during ES as well as mechanisms of the ES effects have never been studied. In a series of studies, we recorded activity of individual spinal neurons recorded in decerebrate cats during treadmill locomotion evoked either by stimulation of the mesencephalic locomotor region (MLR) or by epidural electrical stimulation (ES) of the spinal cord. First, we compared activity of the same neurons during MLR-evoked forward locomotion and ES-evoked forward locomotion. We found that under both conditions, the same neurons had modulation of their activity related to the locomotor rhythm, suggesting that the network generating locomotion under the two conditions is formed by the same neurons. About 40% of these neurons had stable modulation and a similar phase and shape of activity burst in MLR- and ES-evoked locomotor cycles. These neurons may form a part of the locomotor networks that operates similarly under the two conditions and are critical for generation of locomotion. Second, we compared activity of the same neurons during ES-evoked forward locomotion and ES-evoked backward locomotion. Three groups of modulated neurons have been revealed: Group 1 neurons had similar phase of modulation during both FW and BW, Group 2 neurons changed the phase of their modulation in locomotor cycle depending on the direction of locomotion. Group 3 neurons were modulated during FW only or during BW only. We suggest that Group 1 neurons belong to the network generating the vertical component of steps, while Groups 2 and 3 neurons belong to the networks controlling direction of stepping. Third, we analyzed effects of the epidural stimulation upon individual spinal neurons. We found a group of modulated neurons that presumably strongly contribute to initial activation of the locomotor networks, as well as to maintenance of the high level of excitability during ongoing ES-evoked locomotion.

Bio: Dr. Pavel Zelenin is an Associate Professor in the Department of Neuroscience of Karolinska Institute. He received his BS, MS and PhD degrees in Biophysics in the Department of Physics at Moscow State University. In his PhD thesis, he investigated the formation of synaptic connections during regeneration in pteropodal molluscs. He did his postdoctoral work in the lab of Dr. Tatiana Deliagina and Dr. Grigori Orlovsky at Karolinska Institute and investigated brain stem and spinal cord mechanisms of postural control. Currently, Dr. Zelenin investigates the organization and operation of neuronal networks responsible for maintenance of body balance and for control of locomotion after spinal cord injury in lampreys, rabbits and cats.

Host: Boris I. Prilutsky, PhD
Time: 12:00 – 1:00 PM
Location: This seminar will be presented online.

BlueJeans Link

SEMINAR: Wednesday, November 3, 2021

Title: TBA

Ying Zhang, PhD
Department of Medical Neuroscience
Dalhousie University

 

Bio: TBA.

Host: Boris I. Prilutsky, PhD
Time: 12:00 – 1:00 PM
Location: Applied Physiology Building (555 14th Street NW, 30318), Room 1253

BlueJeans Link