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  • 1
    Electronic Resource
    Electronic Resource
    Voluntary rhythmical movement is reset by stimulating the motor cortex (1996)
    Springer
    Experimental brain research 111 (1996), S. 113-120 
    Details
    ISSN: 1432-1106
    Keywords: Cortical stimulation ; Resetting ; Voluntary movement ; Motor cortex
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Using six normal subjects, we mapped the best location for magnetic cortical stimulation to “reset” the phase of a voluntary alternating movement of the right wrist made against three different torques (0.26 N m extension, 0 and 0.09 N m flexion torque) at the subjects' preferred rate. We used “nett resetting” as a measure of phase resetting, based upon the relative amplitudes of the averages of the stimulated and a phase-locked control position record. Nine sites covering a 5 cm square region of the contralateral cortex were systematically stimulated. All the subjects showed evidence of resetting in response to magnetic stimulation over one or more cortical sites during movements made against the extension torque and all subjects demonstrated higher levels of nett resetting under these conditions than in response to similar cortical stimulation during unloaded movements. The best cortical sites for inducing resetting were the same as those from which the largest short-latency responses were evoked in the contralateral forearm flexor and extensor muscles, i.e. the motor cortex. At the cortical sites where magnetic stimulation did induce resetting, the initial electromyographic (EMG) effects consisted of a short-latency excitation followed by a period of inhibition. This silent period was followed by a short burst of excitation often occurring simultaneously in the wrist flexor and extensor muscles, and only thereafter by the return of rhythmical alternating EMG activity characteristic of the wrist movement. The latency to the first rhythmical EMG peak following the stimulus was closely related to the period of the subject's prestimulus movement.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00229560
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Resetting voluntary movement using peripheral nerve stimulation: influence of loading conditions and relative effectiveness (1999)
    Springer
    Experimental brain research 125 (1999), S. 67-74 
    Details
    ISSN: 1432-1106
    Keywords: Key words Resetting ; Magnetic stimulation ; Rhythmical movement ; Human physiology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  The effect of peripheral nerve stimulation on voluntary rhythmic flexion-extension movements at the wrist was studied in nine normal volunteers, and the results compared with the effect of cortical stimulation on the same task. In the first part of the study, magnetic stimulation was given over the inner aspect of the right arm at levels which, at rest, resulted in a wrist flexion twitch of at least 10°. We were able to confirm that this form of (peripheral-nerve) stimulation is an effective means of phase-resetting voluntary wrist movements. In addition, and unlike magnetic stimulation applied over the contralateral motor cortex, changes in the standing torque load, against which the subjects moved, had little influence on the effectiveness of this form of stimulation. Similarly, the amplitude and direction of the averaged first post-stimulus position peak (”P1”), previously identified as important determinants of the resetting induced by a cortical stimulus, were largely independent of the loading torque. In a second part to the study, we directly compared, for a constant loading torque, the resetting induced by magnetic cortical stimulation with that following magnetic stimulation of peripheral nerves. The relationship between the amplitude of P1 and the associated resetting index was identical for both forms of stimulation. Our observations indicate that magnetic stimulation of peripheral nerves is an effective means of resetting voluntary movement. It differs from magnetic cortical stimulation in that the effects of peripheral nerve stimulation are little altered by changes in loading torque. When differences in the size of P1 are allowed for, both peripheral nerve and cortical stimulation are equally effective means of resetting voluntary rhythmical movement.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002210050659
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    The influence of peripheral load on resetting voluntary movement by cortical stimulation: importance of the induced twitch (1997)
    Springer
    Experimental brain research 117 (1997), S. 87-96 
    Details
    ISSN: 1432-1106
    Keywords: Key words Magnetic stimulation ; Resetting ; Motor cortex ; Rhythmical movement ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  We studied the effects of changes in loading torque on the effectiveness of magnetic cortical stimulation in evoking phase resetting of voluntary wrist movement. Nine normal subjects were studied (five on two occasions), while making rhythmical movements of the right wrist, at their preferred rate, against extension torque loads of 0.35 Nm, 0.26 Nm and 0.18 Nm, flexion torque loads of 0.09 Nm and 0.18 Nm and without external load. The position records of individual trials were used to measure the effectiveness of resetting (resetting index: the slope of the phase-response curve) and the ”null phase”, the phase to which the trials were being reset. The loading torque had a strong influence upon both the resetting index and the null phase, generated by a constant intensity of cortical stimulation such that the largest resetting indices were obtained for movements made against the largest extension torque load (mean resetting index 0.72). The degree of resetting and null phase were related to the mean amplitude and direction of the first poststimulus position peak, which in turn was largely determined by the twitch induced by the cortical shock. The timings of the averaged poststimulus position peaks following the first were simple multiples of the prestimulus movement period. Our results indicate that loading conditions profoundly influence the effectiveness of magnetic cortical stimulation in resetting a voluntary movement and that these effects appear to be largely explicable by the changes in the muscle twitch evoked by the stimulus with the different loads. We suggest that the magnetic shock is therefore unlikely to reset voluntary movement by an action directly upon the motor programme. We propose that the main method by which magnetic cortical stimulation resets repetitive wrist movement is indirect: normal generation of repetitive wrist flexion and extension is disrupted by the cortical shock, following which afferent information related to the twitch induced is able to reset the movement.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002210050202
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    Paper (German National Licenses)
    Fulltext
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