title: Integrating multiple sensory systems to modulate neural networks controlling posture.
abstract: In this study we investigated the ability of sensory input to produce tonic responses in hindlimb muscles to facilitate standing in adult spinal rats and tested two hypotheses: 1) whether the spinal neural networks below a complete spinal cord transection can produce tonic reactions by activating different sensory inputs and 2) whether facilitation of tonic and rhythmic responses via activation of afferents and with spinal cord stimulation could engage similar neuronal mechanisms. We used a dynamically controlled platform to generate vibration during weight bearing, epidural stimulation (at spinal cord level S1), and/or tail pinching to determine the postural control responses that can be generated by the lumbosacral spinal cord. We observed that a combination of platform displacement, epidural stimulation, and tail pinching produces a cumulative effect that progressively enhances tonic responses in the hindlimbs. Tonic responses produced by epidural stimulation alone during standing were represented mainly by monosynaptic responses, whereas the combination of epidural stimulation and tail pinching during standing or epidural stimulation during stepping on a treadmill facilitated bilaterally both monosynaptic and polysynaptic responses. The results demonstrate that tonic muscle activity after complete spinal cord injury can be facilitated by activation of specific combinations of afferent inputs associated with load-bearing proprioception and cutaneous input in the presence of epidural stimulation and indicate that whether activation of tonic or rhythmic responses is generated depends on the specific combinations of sources and types of afferents activated in the hindlimb muscles.
authors.affiliation: Departments of Integrative Biology and Physiology and Neurobiology, University of California, Los Angeles, California; Institute of Fundamental Medicine and Biology, Kazan Federal University, Kazan, Russia; and igor.lavrov@gmail.com.
authors.forename: I
authors.initials: I
authors.lastname: Lavrov
authors.affiliation: Departments of Integrative Biology and Physiology and Neurobiology, University of California, Los Angeles, California; Pavlov Institute of Physiology, St. Petersburg, Russia; Institute of Fundamental Medicine and Biology, Kazan Federal University, Kazan, Russia; and.
authors.forename: Y
authors.initials: Y
authors.lastname: Gerasimenko
authors.affiliation: Bioengineering, California Institute of Technology, Pasadena, California.
authors.forename: J
authors.initials: J
authors.lastname: Burdick
authors.affiliation: Departments of Integrative Biology and Physiology and Neurobiology, University of California, Los Angeles, California; Brain Research Institute, University of California, Los Angeles, California;
authors.forename: H
authors.initials: H
authors.lastname: Zhong
authors.affiliation: Departments of Integrative Biology and Physiology and Neurobiology, University of California, Los Angeles, California; Brain Research Institute, University of California, Los Angeles, California;
authors.forename: R R
authors.initials: RR
authors.lastname: Roy
authors.affiliation: Departments of Integrative Biology and Physiology and Neurobiology, University of California, Los Angeles, California; Brain Research Institute, University of California, Los Angeles, California;
authors.forename: V R
authors.initials: VR
authors.lastname: Edgerton
mesh_terms: D000818:Animals; D005260:Female; D006614:Hindlimb / Q000294:innervation / Q000502:physiology*; D018482:Muscle, Skeletal / Q000294:innervation / Q000502:physiology; D009415:Nerve Net / Q000502:physiology*; D011187:Posture; D051381:Rats; D017207:Rats, Sprague-Dawley; D012677:Sensation; D013116:Spinal Cord / Q000502:physiology*; D013569:Synapses / Q000502:physiology
keywords: locomotion; postural control; spinal cord stimulation; spinal cord transection; vibration