The mammalian spinal cord contains pattern generating circuits for locomotion. In addition, there are sensory pathways in the spinal cord that regulate muscular stiffness, inter-joint coordination, and the pattern-generating networks. Evidence exists also that the same sensory information is used to regulate posture and stability in three dimensions during both standing and movement, but the identity of the underlying neural pathways is unknown. The purpose of the proposed project is to build on the work from previous grant cycles and test the hypothesis that the distributed network of spinal pathways from muscle spindle receptors and Golgi tendon organs can mediate appropriate postural responses in three dimensions in a way that resembles the strategy for maintaining balance and stability in normal animals. Alternatively, a neural network in the brainstem might be required for this regulation while the spinal pathways provide more local regulation of the mechanical properties of joints and limbs. In the proposed project, the decerebrate cat preparation will be used to investigate the roles of sensory receptors, neural pathways in the spinal cord, and mechanics of the musculoskeletal system in postural regulation. First, intra-axonal recordings from single muscle spindle receptors and Golgi tendon organs from a variety of muscles will be used to determine the manner in which these receptors respond to translations of the support surface in three dimensions. Second, ground reaction forces and electromyographic responses will be recorded during platform translations to determine whether the strategy used by intact animals can be observed in the decerebrate preparation, and the manner in which the strategy that is observed changes with limb orientation. Third, the organization of intermuscular, sensory pathways will be investigated during treadmill locomotion to understand how spinal mechanisms of balance and stability are altered during locomotion as compared to quiet standing. Demonstration of an intrinsic ability of the spinal cord to regulate posture in three dimensions would greatly facilitate the design of treatments for patients with spinal injury and other motor disorders, since standing and balance are basic to voluntary movement.

Agency
National Institute of Health (NIH)
Institute
National Institute of Neurological Disorders and Stroke (NINDS)
Type
Research Project (R01)
Project #
5R01NS020855-22
Application #
7082186
Study Section
Integrative, Functional and Cognitive Neuroscience 8 (IFCN)
Program Officer
Chen, Daofen
Project Start
1983-09-01
Project End
2008-06-30
Budget Start
2006-07-01
Budget End
2008-06-30
Support Year
22
Fiscal Year
2006
Total Cost
$310,948
Indirect Cost
Name
Emory University
Department
Physiology
Type
Schools of Medicine
DUNS #
066469933
City
Atlanta
State
GA
Country
United States
Zip Code
30322
Honeycutt, Claire F; Nichols, T Richard (2014) The mechanical actions of muscles predict the direction of muscle activation during postural perturbations in the cat hindlimb. J Neurophysiol 111:900-7
Livingston, Beven P; Nichols, T Richard (2014) Effects of reinnervation of the triceps brachii on joint kinematics and electromyographic patterns of the feline forelimb during level and upslope walking. Cells Tissues Organs 199:405-22
Nichols, T Richard; Gottschall, Jinger S; Tuthill, Christopher (2014) The regulation of limb stiffness in the context of locomotor tasks. Adv Exp Med Biol 826:41-54
Livingston, Beven P; Nichols, T Richard (2014) Effects of reinnervation of the biarticular shoulder-elbow muscles on joint kinematics and electromyographic patterns of the feline forelimb during downslope walking. Cells Tissues Organs 199:423-40
Honeycutt, Claire F; Nardelli, Paul; Cope, Timothy C et al. (2012) Muscle spindle responses to horizontal support surface perturbation in the anesthetized cat: insights into the role of autogenic feedback in whole body postural control. J Neurophysiol 108:1253-61
Gottschall, Jinger S; Nichols, T Richard (2011) Neuromuscular strategies for the transitions between level and hill surfaces during walking. Philos Trans R Soc Lond B Biol Sci 366:1565-79
Honeycutt, Claire F; Nichols, T Richard (2010) The decerebrate cat generates the essential features of the force constraint strategy. J Neurophysiol 103:3266-73
Honeycutt, Claire F; Nichols, T Richard (2010) Disruption of cutaneous feedback alters magnitude but not direction of muscle responses to postural perturbations in the decerebrate cat. Exp Brain Res 203:765-71
Nichols, Richard; Ross, Kyla T (2009) The implications of force feedback for the lambda model. Adv Exp Med Biol 629:663-79
Ross, Kyla T; Nichols, T Richard (2009) Heterogenic feedback between hindlimb extensors in the spontaneously locomoting premammillary cat. J Neurophysiol 101:184-97

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