4 research outputs found
Induction of long-term depression-like plasticity by pairings of motor imagination and peripheral electrical stimulation
Long-term depression (LTD) and long-term potentiation (LTP)-like plasticity are models of
synaptic plasticity which have been associated with memory and learning. The induction
of LTD and LTP-like plasticity, using different stimulation protocols, has been proposed
as a means of addressing abnormalities in cortical excitability associated with conditions
such as focal hand dystonia and stroke. The aim of this study was to investigate whether
the excitability of the cortical projections to the tibialis anterior (TA) muscle could be
decreased when dorsiflexion of the ankle joint was imagined and paired with peripheral
electrical stimulation (ES) of the nerve supplying the antagonist soleus muscle. The effect
of stimulus timing was evaluated by comparing paired stimulation timed to reach the
cortex before, at and after the onset of imagined movement. Fourteen healthy subjects
participated in six experimental sessions held on non-consecutive days. The timing of
stimulation delivery was determined offline based on the contingent negative variation
(CNV) of electroencephalography brain data obtained during imagined dorsiflexion.
Afferent stimulation was provided via a single pulse ES to the peripheral nerve paired,
based on the CNV, with motor imagination of ankle dorsiflexion. A significant decrease
(P = 0.001) in the excitability of the cortical projection of TA was observed when the
afferent volley from the ES of the tibial nerve (TN) reached the cortex at the onset
of motor imagination based on the CNV. When TN stimulation was delivered before
(P = 0.62), or after (P = 0.23) imagined movement onset there was no significant
effect. Nor was a significant effect found when ES of the TN was applied independent
of imagined movement (P = 0.45). Therefore, the excitability of the cortical projection
to a muscle can be inhibited when ES of the nerve supplying the antagonist muscle is
precisely paired with the onset of imagined movement
The effects of a single session of spinal manipulation on strength and cortical drive in athletes
Purpose: The primary purpose of this study was to investigate whether a single session of spinal manipulation (SM) increases strength and cortical drive in the lower limb (soleus muscle) of elite Taekwondo athletes. Methods: Soleus-evoked V-waves, H-reflex and maximum voluntary contraction (MVC) of the plantar flexors were recorded from 11 elite Taekwondo athletes using a randomized controlled crossover design. Interventions were either SM or passive movement control. Outcomes were assessed at pre-intervention and at three post-intervention time periods (immediate post, post 30 min and post 60 min). A multifactorial repeated measures ANOVA was conducted to assess within and between group differences. Time and session were used as factors. A post hoc analysis was carried out, when an interactive effect was present. Significance was set at p ≤ 0.05. Results: SM increased MVC force [F(3,30) = 5.95, p < 0.01], and V-waves [F(3,30) = 4.25, p = 0.01] over time compared to the control intervention. Between group differences were significant for all time periods (p < 0.05) except for the post60 force measurements (p = 0.07). Conclusion: A single session of SM increased muscle strength and corticospinal excitability to ankle plantar flexor muscles in elite Taekwondo athletes. The increased MVC force lasted for 30 min and the corticospinal excitability increase persisted for at least 60 min