BackgroundMotor planning, imagery or execution is associated with event-related desynchronization (ERD) of mu rhythm oscillations (8-13 Hz) recordable over sensorimotor areas using electroencephalography (EEG). It was shown that motor imagery involving distal muscles, e.g. finger movements, results in contralateral ERD correlating with increased excitability of the contralateral corticospinal tract (c-CST). Following the rationale that purposefully increasing c-CST excitability might facilitate motor recovery after stroke, ERD recently became an attractive target for brain-computer interface (BCI)-based neurorehabilitation training. It was unclear, however, whether ERD would also reflect excitability of the ipsilateral corticospinal tract (i-CST) that mainly innervates proximal muscles involved in e.g. shoulder movements. Such knowledge would be important to optimize and extend ERD-based BCI neurorehabilitation protocols, e.g. to restore shoulder movements after stroke. Here we used single-pulse transcranial magnetic stimulation (TMS) targeting the ipsilateral primary motor cortex to elicit motor evoked potentials (MEPs) of the trapezius muscle. To assess whether ERD reflects excitability of the i-CST, a correlation analysis between between MEP amplitudes and ipsilateral ERD was performed.MethodsExperiment 1 consisted of a motor execution task during which 10 healthy volunteers performed elevations of the shoulder girdle or finger pinching while a 128-channel EEG was recorded. Experiment 2 consisted of a motor imagery task during which 16 healthy volunteers imagined shoulder girdle elevations or finger pinching while an EEG was recorded; the participants simultaneously received randomly timed, single-pulse TMS to the ipsilateral primary motor cortex. The spatial pattern and amplitude of ERD and the amplitude of the agonist muscle’s TMS-induced MEPs were analyzed.ResultsERDs occurred bilaterally during both execution and imagery of shoulder girdle elevations, but were lateralized to the contralateral hemisphere during finger pinching. We found that trapezius MEPs increased during motor imagery of shoulder elevations and correlated with ipsilateral ERD amplitudes.ConclusionsIpsilateral ERD during execution and imagery of shoulder girdle elevations appears to reflect the excitability of uncrossed pathways projecting to the shoulder muscles. As such, ipsilateral ERD could be used for neurofeedback training of shoulder movement, aiming at reanimation of the i-CST.
Oxidation resistance of TiAl3, one of the candidates of coating materials for high
temperature structural materials such as Ti3Al and TiAl, has been studied. Specimens were prepared
by forming TiAl3 in Al/Ti/Al reaction diffusion couples at 923 K and then TiAl3 layer was exposed
to air by dissolving Al plate in a 1N NaOH solution. The obtained TiAl3/Ti/TiAl3 couples were
annealed in air in the temperature range from 1173 K to 1468 K. The oxidation rate was compared
with that determined by using bulk TiAl3. The present data show a bend on the Arrhenius plot of
parabolic phase growth rate constant, k2, at 1323 K. Above 1323K, the constant coincides well with
the extrapolated values of bulk data while the value in the lower temperature range is larger than
that of bulk specimens.
During the oxidation experiments, intermetallic compounds Ti3Al, TiAl and TiAl2 were formed
between Ti and TiAl3. Interdiffusion coefficients in the Ti3Al, TiAl phases determined from these
diffusion couples are more than one order of magnitude larger than the interdiffusion coefficients
determined by previous investigators from single-phase diffusion couples but coincide with the
coefficients determined from multi-phase diffusion couples. This difference between interdiffusion
coefficients has been discussed and explained by the effect of boundary diffusion in the diffusion
layers formed in the multi-phase diffusion couples.
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