Paul S.G. Stein, Ph.D.
212 Monsanto Laboratory
behavior, central pattern generators, neurobiology, physiology, spinal cord
Sensorimotor integration; spinal cord neural networks; turtle hindlimb motor output
Tactile inputs excite neural networks in the spinal cord that produce patterns of motor output responsible for specific behaviors (Stein, 2005, 2008, 2010). We study the physiology of spinal networks that generate the scratch reflex. A turtle with a complete transection of the spinal cord exhibits a scratch reflex in response to tactile stimulation of a specific site on the body surface. During a scratch, a limb reaches toward and rubs against the stimulated site. We stimulate sites on the turtle shell to elicit three different types or "forms" of scratching. We have characterized the patterns of muscular activation during these three forms. After immobilization of the spinal turtle with a neuromuscular blocking agent, tactile stimulation of a specific site will elicit a pattern of motor neuron activity that is an excellent replica of the sequence of muscle activity recorded in the mobile preparation. This pattern, recorded from peripheral nerves of the immobilized animal, is termed "fictive" since it occurs in the absence of actual movements. We test hypotheses of modular spinal cord motor pattern generation. We study preparations that can produce either a flexor rhythm, an extensor rhythm, or rhythmic alternation between flexor and extensor activation. We use extracellular microsuction electrodes to obtain single-unit axonal recordings of interneurons. These recordings provide support for the concept of modular spinal cord organization (Stein and Daniels-McQueen, 2002, 2004; Stein, 2005, 2008, 2010; Stein et al., 2016).
Stein PSG, Daniels-McQueen S, Lai J, Liu Z, Corman TS (2016) Modular organization of the multipartite central pattern generator for turtle rostral scratch: knee-related interneurons during deletions. J Neurophysiol 115: 3130-3139. http://www.ncbi.nlm.nih.gov/pubmed/27030737
Stein PSG (2013) Molecular, genetic, cellular, and network functions in the spinal cord and brainstem. Ann NY Acad Sci 1279: 1-12. http://www.ncbi.nlm.nih.gov/pubmed/23530997
Stein PSG (2010) Alternation of agonists and antagonists during turtle hindlimb motor rhythms. Ann NY Acad Sci 1198: 105-118. http://www.ncbi.nlm.nih.gov/pubmed/20536925
Stein PSG (2008) Motor pattern deletions and modular organization of turtle spinal cord. Brain Res Rev 57: 118-124. http://www.ncbi.nlm.nih.gov/pubmed/17826841
Stein PSG (2005) Neuronal control of turtle hindlimb motor rhythms. J Comp Physiol A Neuroethol Sens Neural Behav Physiol 2005 191: 213-229. http://www.ncbi.nlm.nih.gov/pubmed/15452660
Stein PSG, Daniels-McQueen S (2004) Variations in motor patterns during fictive rostral scratching in the turtle: Knee-related deletions. J Neurophysiol 91: 2380-2384. http://www.ncbi.nlm.nih.gov/pubmed/14724267
Stein PSG, Daniels-McQueen S (2002) Modular organization of turtle spinal interneurons during normal and deletion fictive rostral scratching. J Neurosci 22: 6800-6809. http://www.jneurosci.org/content/22/15/6800
Stein PSG, McCullough ML, Currie SN (1998) Reconstruction of flexor/extensor alternation during fictive rostral scratching by two-site stimulation in the spinal turtle with a transverse spinal hemisection. J Neurosci 18:467-479. http://www.jneurosci.org/content/18/1/467
Robertson GA, Stein PSG (1988) Synaptic control of hindlimb motoneurones during three forms of the fictive scratch reflex in the turtle. J Physiol (London) 404:101-128. http://jp.physoc.org/content/404/1/101
Robertson GA, Mortin LI, Keifer J, Stein PSG (1985) Three forms of the scratch reflex in the spinal turtle: central generation of motor patterns. J Neurophysiol 53:1517-1534. http://jn.physiology.org/content/53/6/1517
Last Updated: 6/23/2016 9:49:17 AM
I am a co-editor of the 2010 volume titled Neurons and Networks in the Spinal Cord, published in the Annals of the New York Academy of Sciences.