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Irina I. Beloozerova, Ph. D.
Department of Neurobiology
Barrow Neurological Institute
Abstract
Results of a number of studies suggest that movements of different segments of the limb are controlled differently during locomotion. Several lines of evidence suggest that distinct neuronal mechanisms underlie the difference in the control. These mechanisms, however, have been never explicitly studied until recently. In my talk, I will present our findings of differential activities of the shoulder, elbow, and wrist-related populations of neurons in the thalamo-cortical network during simple locomotion and accurate stepping on a complex terrain.
In chronically instrumented cats walking on a flat surface and along a horizontal ladder we have recorded the activity of single neurons in the primary motor and somatosensory cortices, and all neurons from motor cortex and many from somatosensory cortex were identified as pyramidal tract projecting neurons (PTNs, Stout and Beloozerova, 2012; Favorov et al., 2015). We have also recorded the activity of neurons in the motor thalamus, most of which were identified as thalamo-cortical projecting neurons (TCs) of the ventrolateral thalamus (VL, Marlinski et al., 2012a). In addition, we have recorded the activity of inhibitory interneurons of the motor compartment of the reticular nucleus of the thalamus (RE, Marlinski et al., 2012b; Marlinski and Beloozerova, 2014). We grouped the neurons according to the location of their receptive field into shoulder-, elbow, and wrist/paw-related subpopulations. We compared the step cycle-related activity of these subpopulations within each of the motor centers, as well as the activity of populations with the same receptive field from different centers. We found significant differences in both comparisons.
Our data suggest strategic differences in the thalamo-cortical controls for the shoulder, elbow, and wrist during locomotion (Beloozerova et al., 2013). The activity of the RE is at the heart of these differences. Commands controlling the shoulder only moderately activate inhibitory RE neurons, so the ascending thalamo-cortical signals related to the shoulder, which come from the cerebellum and spinal cord, can reach motor cortex at any time during the stride. In contrast, commands controlling the wrist significantly enhance the activity of inhibitory RE neurons during the swing phase. This is likely to attenuate thalamo-cortical signals during the swing phase, so that other inputs to motor cortex such as inputs along the cortico-cortical pathways may have a larger contribution to the control of the motor cortical output related to the wrist during the swing phase of the stride.
About the Speaker
Dr. Irina Beloozerova studies the organization and function of motor systems, particularly, neuronal mechanisms and biomechanics of locomotion and posture. Her goal is to understand how locomotion and posture are controlled by the nervous system and adapt to the environment. Irina has investigated the mechanisms of locomotion and posture in mollusks, rabbits, cats, and non-human primates. Her latest work is in chronically instrumented and freely behaving cats. In these experiments, she uses single-unit recordings, biomechanical analysis, and pharmacological and optogenetic manipulations to understand the organization of locomotion and posture.Dr. Irina Beloozerova graduated in 1981 from the Lomonosov University in Moscow, Russia, with a degree in biology. She received her early training in neuroscience as a Master’s student working in mollusks under Drs. Orlovsky and Arshavsky. Thereafter, Irina worked 12 years in the Soviet Space program studying limbsand eye-head coordination in Rhesus monkeys. During that time she also completed her PhD as a self-directed study of cortical mechanisms of visually guided locomotion in cats. Her postdoctoral training was with Dr. Armstrong at the University of Bristol, UK; Dr. Rossignol at the University of Montreal, Canada; and Dr. Swadlow at the University of Connecticut, USA. Irina has been a faculty member of the Barrow Neurological Institute in Phoenix, Arizona since 2000. She established two research programs: one in the thalamo-cortical mechanisms of visually guided locomotion and another, in the supra-spinal control of posture. Irina’s laboratory has been funded by several NIH R01 grants, two smaller NIH awards, and an NSF grant. Irina published 58 full size research papers and 10 reviews, and founded a Cat-Brain database, an open database of cat neuronal activity and body biomechanics.
Physiology Brownbag Seminars
The Physiology Group in the School of Biological Sciences hosts Brownbag Lunchtime Seminars twice a month on Wednesdays at noon in room 1253 of the Applied Physiology Building located at 555 14th Street NW, Atlanta, GA 30318. You are welcome to bring a lunch and join us as we ruminate with us on topics in Physiology! A full listing of seminars can be found at http://pwp.gatech.edu/bmmc/physiology-brownbag-seminars-fall-2018/.
