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Biomedical subjects

R A Ashley

Publications and source records attributed to R A Ashley.

22 records · Page 2Linked to original sources
PubMedDate not supplied

Relationship between the size of the recording electrodes and morphology of the compound muscle action potentials.

To determine the effect of recording electrode size on the compound muscle action potentials (CMAPs), maximally evoked CMAPs were obtained from the abductor digiti minimi muscle in ten normal subjects with circular-shaped surface recording electrodes of different diameters (4, 6, 8, 10, 12, and 14 mm). The electrodes were concentrically located on the same recording point on the muscle at its endplate zones when obtaining the CMAPs. The CMAP onset latency remained unchanged for all recording electrode sizes. The CMAP amplitude decreased with increasing electrode size. The mean absolute amplitude difference between CMAPs recorded with a 4-mm diameter electrode and those with a 14-mm diameter electrode was 1.22 mV, representing an amplitude decrement of 10% with this increase in electrode size. The general shape or morphology of the CMAPs was relatively well preserved.

Action Potentials↗
PubMedDate not supplied

Vibrations and sounds produced during sustained voluntary muscle contraction.

In 20 normal subjects, sounds or vibrational signals were recorded from the biceps brachii muscle during voluntary isometric contraction. Fourier analysis showed presence of predominantly low frequency components with little contributions beyond 60 or 70 Hz. Relatively high amplitude peaks occurring below 20 Hz were seen in the frequency spectrum with the most prominent of these peaks occurring at a mean frequency of 11.3 Hz. A majority of subjects had one or two additional peaks, each appearing on either side of the major peak with mean frequencies of 7.3 and 16.2 Hz. In general, subjects who could not sustain a very steady contraction had more peaks compared to those who were able to maintain a smoother contraction. Between 20 and 50 Hz, several well-defined but much smaller peaks were also seen. The frequencies of some of these small peaks can be expressed as exact harmonics of the previously described larger peaks in 85% of subjects.

Adult↗
PubMedDate not supplied

Radial sensory innervation to index and middle fingers: electrophysiologic considerations.

Antidromic radial and median compound sensory nerve action potentials (CSNAPs) were recorded from the index and middle fingers in 20 subjects. No appreciable radial sensory response can be seen at the middle finger. Seventy-five percent of subjects had radial CSNAPs at the index finger, seen to a variable extent along the finger, with 40% having a response limited only to the base of the first phalanx. Radial CSNAP amplitude was small compared to median CSNAP (ratio = 0.16). Because of the small size and wide variability among individuals, radial CSNAPs from index and middle fingers seem to have limited direct clinical utility. Contamination of median CSNAPs by radial CSNAPs is negligible or absent (when there is unavoidable spread of the stimulus to the radial nerve), if median sensory responses are recorded from the distal half of the index or middle finger.

Action Potentials↗