Input-output functions of mammalian motoneurons

Powers, Randall K.; Binder, Marc D.

doi:10.1007/bfb0115594

Cited by 244 publications

(286 citation statements)

References 370 publications

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“…Increased monoaminergic input to motoneurons originating from the metabotropic outputs of the raphe nucleus (Alvarez et al 1998) and locus coeruleus nucleus (Giroux et al 1999) is known to result in increased spinal motoneuronal excitability (Heckman et al 2003). In addition to the neuromodulatory influences on motoneurons, primary descending input for volitional movement is likely through an ionotropic mechanism (Powers and Binder 2001). Descending pontomedullary reticular formation output to the limbs is shown primarily to be from shoulder abductors and elbow flexors (Davidson and Buford 2004) and contribute to the bilateral control of reaching movements in the cat (Schepens and Drew 2004) and monkey (Davidson and Buford 2006).…”

Section: Discussionmentioning

confidence: 99%

Position-dependent torque coupling and associated muscle activation in the hemiparetic upper extremity

et al. 2006

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Previous studies have demonstrated abnormal joint torque coupling and associated muscle coactivations of the upper extremity in individuals with unilateral stroke. We investigated the effect of upper limb configuration on the expression of the well-documented patterns of shoulder abduction/ elbow flexion and shoulder adduction/elbow extension. Maximal isometric shoulder and elbow torques were measured in stroke subjects in four different arm configurations. Additionally, an isometric combined torque task was completed where subjects were required to maintain various levels of shoulder abduction/adduction torque while attempting to maximize elbow flexion or extension torque. The dominant abduction/elbow flexion pattern was insensitive to changes in limb configuration while the elbow extension component of the adduction/extension pattern changed to elbow flexion at smaller shoulder abduction angles. This effect was not present in control subjects without stroke. The reversal of the torque-coupling pattern could not be explained by mechanical factors such as muscle length changes or muscle strength imbalances across the elbow joint. Potential neural mechanisms underlying the sensitivity of the adduction/elbow extension pattern to different somatosensory input resultant from changes in limb configuration are discussed along with the implications for future research.

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Section: Discussionmentioning

confidence: 99%

Position-dependent torque coupling and associated muscle activation in the hemiparetic upper extremity

et al. 2006

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“…This article begins with a review of Eccles' contributions to our early understanding of motoneuron physiology, moves on to early studies in repetitive firing behavior by Ragnar Granit (1900-1991, Daniel Kernell, and their colleagues, and then addresses our current understanding of motoneuronal activity during behavior. My intent is not to provide a comprehensive review of motoneuron physiology, which can be found elsewhere (e.g., Rekling et al, 2000;Powers and Binder, 2001). Nor is this article a thorough historical analysis of Eccles' contributions (for such references, see Curtis and Andersen, 2001;Stuart and Pierce, 2006).…”

Section: Introductionmentioning

confidence: 99%

Beginning at the end: Repetitive firing properties in the final common pathway

Brownstone

2006

Progress in Neurobiology

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Since the early 20th century, it has been recognized that motoneurons must fire repetitive trains of action potentials to produce muscle contraction. In 1932, Sir John Eccles, together with Hebbel Hoff, found that action potential spike trains in motor axons were produced by "rhythmic centres", which were within the motoneurons themselves. Two decades later, Eccles attended a Cold Spring Harbor Symposium in NY, USA entitled "The Neuron". Two of the many notable presentations at this symposium were juxtaposed: one by Eccles from the University of Otago, Dunedin, NZL, and the other by J. Walter Woodbury and Harry Patton from the University of Washington, Seattle, USA. Both presentations included data obtained using sharp microelectrodes to study the intracellularly recorded potentials of cat motoneurons. In this review, I discuss some of the events leading up to and surrounding this jointly accomplished advance and proceed to discussion of subsequent studies over 5+ decades that have made use of intracellular recordings from motoneurons to study their repetitive firing behavior. This begins with early descriptions of primary and secondary range firing, and continues to the discovery of dendritic persistent inward currents and their relation to plateau potentials, synaptic amplification, and motoneuronal firing. Following a brief description of the possible mechanisms underlying spike frequency adaptation, I discuss the modulation of repetitive firing properties during various motor behaviors. It has become increasingly clear that the central nervous system has exquisite control of the repetitive firing of motoneurons. Eccles' work laid the foundation for the present-day study of these processes.

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“…The neuroinflammation response is a promising approach (Philips and Robberecht, 2011); another could be to manipulate neuromodulatory input to the spinal cord. Serotonin (5HT) and norepinephrine (NE) have potent effects on motoneurons, including increasing PIC amplitude, decreasing input conductance, hyperpolarizing spike threshold, and depolarizing resting potential (Hounsgaard and Kiehn, 1989, Lee and Heckman, 1999, Powers and Binder, 2001, Alaburda et al, 2002, Hultborn et al, 2004, Perrier and Delgado-Lezama, 2005, Heckman et al, 2008. Furthermore, neuromodulators are constantly scaling the level of activation of motoneurons as needed (Heckman et al, 2004).…”

Section: Future Directionsmentioning

confidence: 99%