Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale
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Neck muscle vibration (NMV) during upright standing is known to induce forward leaning, which has been explained as a global response to the (illusory) perception of a lengthening of the dorsal neck muscles. However, the effects of NMV both at the level of individual joints and on whole-body postural coordination, and its potential modulation by vision, have not yet been analyzed in detail. Eight healthy young adult participants completed a total of ten trials each, with a 10-s period of unperturbed standing followed by a 10-s period of NMV. ⋯ In contrast, motor-equivalent stabilization of CoM and head position, and trunk orientation was only observed during no-vibration periods. Taken together, our results demonstrate specific effects of vision and proprioception on different aspects of local and global postural control. While perturbed neck proprioception seemed to affect the postural "set point" (inducing forward leaning), vision appeared to mainly serve in noise reduction (residual fluctuations) and control of head orientation.
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When two motor cortical stimuli are delivered with an interstimulus interval of 50-200 ms, the response (motor evoked potential; MEP) to the second stimulus is typically suppressed. This phenomenon is termed long-interval intracortical inhibition (LICI), although data from one subject suggest that facilitation is possible. Moreover, we recently showed that suppression can be mediated at a spinal level. ⋯ In a subset of subjects, cervicomedullary stimulation was used to activate the corticospinal tract to identify possible spinal influences on changes to MEPs. Contraction strength and test stimulus intensity each had different effects on unconditioned and conditioned MEP size, and hence, LICI is highly dependent on both factors. Further, because motoneurons are facilitated during contraction but disfacilitated after a strong conditioning stimulus, the standard ratio of LICI is of questionable validity during voluntary contractions.
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Randomized Controlled Trial
The role of spatial attention in attentional control over pain: an experimental investigation.
Distraction is a common method of pain control that is often found to be effective. However, it is still largely unexplored which components of distraction are responsible for its effects. This study investigated the role of the spatial location of task-relevant stimuli in the effectiveness of distraction. ⋯ In a second experiment, we examined whether the manipulation of spatial location affects the experience of pain. Overall, results indicated that directing attention away from the pain location results in a slower response to painful stimuli and a reduction in pain. It may be concluded that the analgesic effect of distraction is at least partly the result of the spatial location of the distracting information.
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Recent experiments have identified neuromechanical interactions between the arms and legs during human locomotor movement. Previous work reported that during the rhythmic movement of all four limbs, the influence of the arms on reflex expression in the legs was superimposed on the dominant effect of the legs. This evidence was based upon studies using cutaneous and H-reflex modulation as indices of neuronal activity related to locomotion. ⋯ These findings provide definitive evidence for interlimb coupling between cervical and lumbar oscillators in gating the excitability of reflex pathways to a leg muscle for different populations of motorneurons within the pool. This further supports the contention of similar functional organization for locomotor networks in the human when compared to other animals. Additionally, these data provide additional confirmation of the significant role of the output of neural control for rhythmic arm movement in modulating reflex excitability of the legs that is specifically adjusted according to the phase and task.
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The aim of the current study was to identify whether hyperexcitability of the central nervous system is a prognostic factor for individuals with carpal tunnel syndrome (CTS) likely to experience rapid and clinical self-reported improvement following a physical therapy program including soft tissue mobilization and nerve slider neurodynamic interventions. Women presenting with clinical and electrophysiological findings of CTS were involved in a prospective single-arm trial. Participants underwent a standardized examination and then a physical therapy session. ⋯ We identified 3 factors that may be associated with a rapid clinical response to both soft tissue mobilization and nerve slider neurodynamic techniques targeted to the median nerve in women presenting with CTS. Our results support that widespread central sensitization may not be present in women with CTS who are likely to achieve a successful outcome with physical therapy. Future studies are now necessary to validate these findings.