The spinal cord exhibits motor function after all neuronal connections with supraspinal structures are severed. Our work contributes to spinal motor neurophysiology by examining the neuronal mechanisms responsible for the production of three types of scratch reflexes in the spinal turtle. The sequences of motor neuron activity patterns characteristic of each type of scratch are produced in a spinal turtle immobilized with neuromuscular blockade. This preparation has the mechanical stability to allow intracellular recordings from spinal cord neurons during the production of scratch reflex motor activity. We will characterize the excitatory and inhibitory synaptic potentials in motor neurons during the three forms of the scratch reflex using intracellular recording techniques. We will use these data to predict the timing characteristics of spinal interneurons generating the scratch reflex. We will examine the activity patterns of spinal interneurons directly during these reflexes using both intracellular and extracellular recording techniques. We will examine restricted preparations consisting of two to four segments of the spinal cord that are capable of producing scratch motor patterns. We will use these data to determine the segmental locations of the interneurons generating each of the forms of the scratch reflex. We will develop in vitro preparations using these restricted portions of the spinal cord suitable for pharmacological manipulations of the generator network. We will use our PDP-11/23+ computer to analyze the motor patterns during the scratch and will develop graphical techniques for computer pattern recognition of the scratch motor patterns. We will study blends of several forms of the scratch reflex that are produced by simultaneous stimulation of two sites on the body surface in order to determine the rules of selection and interruption of motor programs. We will use our data to test a set of working hypotheses concerning the interneuronal organization of spinal cord motor pattern generators. Since the spinal cord of humans is similar to that of the lower vertebrates, our work will serve as useful working hypotheses for those currently developing neural motor prostheses for spinal-injured humans.

Agency
National Institute of Health (NIH)
Institute
National Institute of Neurological Disorders and Stroke (NINDS)
Type
Research Project (R01)
Project #
2R01NS015049-07
Application #
3395922
Study Section
Neurology B Subcommittee 1 (NEUB)
Project Start
1979-09-24
Project End
1989-02-28
Budget Start
1986-03-01
Budget End
1987-02-28
Support Year
7
Fiscal Year
1986
Total Cost
Indirect Cost
Name
Washington University
Department
Type
Schools of Arts and Sciences
DUNS #
062761671
City
Saint Louis
State
MO
Country
United States
Zip Code
63130
Stein, P S; Victor, J C; Field, E C et al. (1995) Bilateral control of hindlimb scratching in the spinal turtle: contralateral spinal circuitry contributes to the normal ipsilateral motor pattern of fictive rostral scratching. J Neurosci 15:4343-55
Currie, S N; Stein, P S (1990) Cutaneous stimulation evokes long-lasting excitation of spinal interneurons in the turtle. J Neurophysiol 64:1134-48
Mortin, L I; Stein, P S (1990) Cutaneous dermatomes for initiation of three forms of the scratch reflex in the spinal turtle. J Comp Neurol 295:515-29
Mortin, L I; Stein, P S (1989) Spinal cord segments containing key elements of the central pattern generators for three forms of scratch reflex in the turtle. J Neurosci 9:2285-96
Stein, P S (1989) Spinal cord circuits for motor pattern selection in the turtle. Ann N Y Acad Sci 563:1-10
Currie, S N; Stein, P S (1989) Interruptions of fictive scratch motor rhythms by activation of cutaneous flexion reflex afferents in the turtle. J Neurosci 9:488-96
Stein, P S; Schild, C P (1989) N-methyl-D-aspartate antagonist applied to the spinal cord hindlimb enlargement reduces the amplitude of flexion reflex in the turtle. Brain Res 479:379-83
Currie, S N; Stein, P S (1988) Electrical activation of the pocket scratch central pattern generator in the turtle. J Neurophysiol 60:2122-37
Stein, P S (1988) Motor mechanisms in the turtle spinal cord. Acta Biol Hung 39:155-60
Stein, P S; Camp, A W; Robertson, G A et al. (1986) Blends of rostral and caudal scratch reflex motor patterns elicited by simultaneous stimulation of two sites in the spinal turtle. J Neurosci 6:2259-66

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