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Recruitment of extensor-carpi-radialis motor units by transcranial magnetic stimulation and radial-nerve stimulation in human subjects (1999)

Morita, H. ; Baumgarten, J. ; Petersen, N. ; [et al.]

Springer

Experimental brain research 128 (1999), S. 557-562

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ISSN: 1432-1106

Keywords: Key words H-reflex ; Motor units ; Motor evoked potentials ; Motoneuron recruitment ; Transcranial magnetic stimulation

Source: Springer Online Journal Archives 1860-2000

Topics: Medicine

Notes: Abstract The responses of 34 extensor-carpi-radialis motor units to graded transcranial magnetic stimulation (TMS) and electrical stimulation of the radial nerve were investigated in six human subjects. Simultaneously with the recording of the single motor-unit discharges, motor-evoked potentials (MEPs) and H-reflexes evoked by the two types of stimulation were recorded by surface electrodes and expressed as a percentage of the maximal motor response (Mmax). Ten motor units were activated in the H-reflex when it was less than 5% of Mmax, but not in the MEP even when it was 15% of Mmax. The opposite was observed for three motor units. Eleven motor units were recruited by both stimuli, but with significantly different recruitment thresholds. Only ten motor units had a threshold similar to TMS and radial nerve stimulation. From these observations, we suggest that caution should be taken when making conclusions regarding motor cortical excitability based on changes in the size of MEPs, even when it is ensured that there are no similar changes in background EMG-activity or H-reflexes.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/s002210050881

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Comparison between experimental and calculated relative escape peak intensities for an intrinsic Ge detector in the energy region 11-25 keV (1979)

Christensen, L. H.

New York, NY [u.a.] : Wiley-Blackwell

X-Ray Spectrometry 8 (1979), S. 146-148

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ISSN: 0049-8246

Keywords: Chemistry ; Analytical Chemistry and Spectroscopy

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Physics

Notes: Experimental measurements of the relative intensity of the escape peak produced in an intrinsic Ge detector agree quite well with the calculated intensities based on a theoretical model. Contrary to the Si(Li) detector Kα as well as Kβ escape peaks are observed. In the energy region 11-25 keV the Ge Kα escape peak intensities vary from 16.3 to 4.7% and the Ge Kβ escape peak from 2.4 to 0.9% of that to the parent line. Therefore, the escape peaks are not negligible in X-ray fluorescence analysis, and it may be necessary to numerically correct for them or, by a suitable choice of excitation energy, avoid them completely.

Additional Material: 1 Ill.