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  • 1
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    German Medical Science GMS Publishing House; Düsseldorf
    In:  68. Jahrestagung der Deutschen Gesellschaft für Neurochirurgie (DGNC), 7. Joint Meeting mit der Society of British Neurological Surgeons (SBNS); 20170514-20170517; Magdeburg; DOCP 037 /20170609/
    Publication Date: 2017-06-09
    Keywords: ddc: 610
    Language: English
    Type: conferenceObject
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  • 2
    ISSN: 1432-1106
    Keywords: Key words Transcranial magnetic stimulation ; Plasticity ; Synchronization ; Motor system ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  We used focal transcranial magnetic stimulation to examine the effects of 120 synchronized thumb and foot movements on the motor output map of the right abductor pollicis brevis muscle (APB) (experiment 1). To evaluate the performance, the latencies between the onset of the electromyographic activity (EMG) of the two muscles were measured. As control, 120 asynchronous thumb and foot movements were performed (experiment 2). Exclusively in experiment 1, the center of gravity (CoG) of the output map moved medially in the direction of the foot representation area (mean 7 mm, P〈0.05) and returned into its original location within 1 h. In experiment 2, the CoG remained unchanged (mean displacement, 0.68 mm into a lateral direction; not significant). The effect in experiment 1 was independent of an improvement in performance. We conclude that a short-lasting training of synchronous movements induces modulations of motor output maps which probably occur due to interactions between hand and foot representation areas in the motor cortex.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-1106
    Keywords: Key words Somatotopy ; Input-Output ; Inhibition ; Excitation ; Transcranial magnetic stimulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Integration of tactile afferent signals with motor commands is crucial for the performance of purposeful movements such as during manipulation of an object in the hand. To study the somatotopic organization of sensorimotor integration we applied electrical peripheral conditioning stimuli to a digit located near (homotopic stimulation) or distant from (heterotopic stimulation) relaxed or isometrically contracted intrinsic hand muscles at variable time intervals prior to transcranial magnetic stimulation (TMS). Cutaneous stimulation has previously been shown to modulate the amplitude of the motor evoked potential (MEP) and to shorten the duration of the silent period (SP) evoked by TMS. In relaxed target muscles the time-dependent modulation of TMS-evoked motor responses by homotopic conditioning stimulation differed from modulation by heterotopic stimulation. Similar differences in the modulation pattern evoked by homotopic and heterotopic conditioning stimulation were observed for two distinct target muscles of the hand (abductor digiti minimi, abductor pollicis brevis muscle). Differences in modulation were maximal when the conditioning stimulation was applied 25–30 ms and 150–200 ms prior to TMS. Comparison of the modulation of the amplitudes of MEPs evoked by transcranial electrical stimulation (TES) and the modulation of those evoked by TMS suggests that differences between homotopic and heterotopic stimulation originate subcortically at 25- to 30-ms and, at least partially, cortically at 150- to 200-ms interstimulus intervals. In isometrically contracted intrinsic hand muscles the degree to which the SP was shortened reflected the location and the timing of the conditioning stimulus. Shortening was maximal when the conditioning stimulus was applied nearest to the contracted target muscle and 20 ms prior to the test stimulus. In contrast to the SP duration, the MEP size in voluntarily contracted target muscles was unaffected by the location of the conditioning stimulus. The somatotopic gradient of SP shortening was abolished when the two target muscles were simultaneously activated isometrically. Together, our findings suggest that somatotopy of input-output relationships is implemented at both a spinal and a cortical level in the human central nervous system and may also depend on the motor task involved.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-1106
    Keywords: Key words Intracortical inhibition ; Transcranial magnetic stimulation ; Motor exercise ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  The motor-evoked potential (MEP) to transcranial magnetic stimulation (TMS) is inhibited when preceded by a subthreshold TMS stimulus at short intervals (1–6 ms; intracortical inhibition, ICI) and is facilitated when preceded by a subthreshold TMS at longer intervals (10–15 ms; intracortical facilitation, ICF). We studied changes in ICI and ICF associated with two motor tasks requiring a different selectivity in fine motor control of small hand muscles (abductor pollicis brevis muscle, APB, and fourth dorsal interosseous muscle, 4DIO). In experiment 1 (exp. 1), nine healthy subjects completed four sets (5 min duration each) of repetitive (1 Hz) thumb movements. In experiment 2 (exp. 2), the subjects produced the same number of thumb movements, but complete relaxation of 4DIO was demanded. Following free thumb movements (exp. 1), amplitudes of MEPs in response to both single and paired TMS showed a trend to increase with the number of exercise sets in both APB and 4DIO. By contrast, more focal, selective thumb movementsinvolving APB with relaxation of 4DIO (exp. 2) caused an increase in MEP amplitudes after single and paired pulses only in APB, while a marked decrease in MEPs after paired pulses, but not after single TMS, in the actively relaxed 4DIO. This effect was more prominent for the interstimulus interval (ISI) of 1–3 ms than for longer ISIs (8 ms, 10 ms, and 15 ms). F-wave amplitudes reflecting excitability of the alpha motoneuron pool were unaltered in APB and 4DIO, suggesting a supraspinal origin for the observed changes. We conclude that plastic changes of ICI and ICF within the hand representation vary according to the selective requirements of the motor program. Performance of more focal tasks may be associated with a decrease in ICI in muscles engaged in the training task, while at the same time ICI may be increased in an actively relaxed muscle, also required for a focal performance. Additionally, our data further supports the idea that ICI and ICF may be controlled independently.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1435-1463
    Keywords: Silent period ; transcallosal stimulation ; magnetic stimulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The present study was performed in order to determine the influence of ipsilateral transcranial magnetic stimulations (TMS) on the silent period evoked by contralateral cortical stimulations. Ipsilateral TMS preceded the contralateral magnetic or electrical cortex stimulation by 0–50ms. In all subjects, the duration of the silent period was decreased in interstimulus intervals of 20–30ms when using magnetic ipsi- and contralateral stimuli. No change in the silent period was seen with ipsilateral magnetic and contralateral electrical stimulations. Decreases of motor evoked potential amplitudes were an inconsistant phenomenon. The results indicate that ipsilateral TMS in activate inhibitory cortical interneurons, probably via transcallosal pathways. Different time courses and different degrees of inhibition indicate that motor excitation and inhibition may be mediated by different neuronal circuits.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1435-1463
    Keywords: Transcranial magnetic stimulation ; riluzole ; glutamate ; intracortical inhibition ; intracortical facilitation ; silent period
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The effect of the glutamate antagonist riluzole on excitatory and inhibitory phenomena in the human motor system was studied by transcranial magnetic stimulation (TMS) and peripheral electrical nerve stimulation. The motor threshold, the intracortical inhibition and intracortical facilitation as assessed by paired TMS, the cortical and peripheral silent periods, F wave amplitudes and F wave latencies were measured. Riluzole suppressed the intracortical facilitation whereas other parameters remained unchanged, indicating that the neurotransmitter glutamate is mainly involved in facilitatory mechanisms in the motor system.
    Type of Medium: Electronic Resource
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