Mean Spike Duration Research Articles

Spike shape analysis of surface electromyographic activity in wrist flexor and extensor muscles of the world's fastest drummer

Spike shape analysis (SSA) is a method to infer motor unit (MU) activity by examining interference pattern of surface electromyography (sEMG). SSA has succeeded to assess neuromuscular adaptations after dynamic training; however, it has not been used to assess muscle activities during the dynamic movements as seen in music performance. The present study used SSA to investigate sEMG activities of wrist flexor and extensor muscles in the winner of a contest to find the world's fastest drummer (WFD) during performing rhythmic wrist flexion/extension movements with one hand using a handheld drumstick. SSA measures of the WFD were compared with those in the two control groups: non-drummers (NDs) and ordinary drummers (ODs). We found that the WFD showed significantly high mean spike frequency (MSF), short mean spike duration (MSD), and small mean number of peaks per spike (MNPPS) compared with the control groups. These results suggest that the WFD had exceptional MU activity such as higher MU discharge rate, more MU recruitment, and/or higher MU synchronization to achieve extraordinary fast 10-Hz drumming performance. SSA will be useful to investigate the muscle activity seen in music performance.

Effects of monopolar and bipolar electrode configurations on surface EMG spike analysis

This study compared the effects of monopolar and bipolar electrode configurations on interference pattern analysis of the surface electromyographic (sEMG). Twenty-four college-aged male participants performed isometric actions of the elbow flexors at 40, 60, 80, and 100 percent of maximal voluntary contraction (MVC). Separate (Ag/AgCl) electrodes were used for both configurations. There were five measures associated with “spike shape” analysis: mean spike amplitude (MSA), mean spike frequency (MSF), mean spike slope (MSS), mean spike duration (MSD) and mean number of peaks per spike (MNPPS). A load-cell and wrist-cuff assembly was used to record isometric elbow flexion forces. Both electrode configurations resulted in the same trends force changes in spike shape measures across force levels: there was a linear increase in MSA, MSS, and a quadratic decrease in MSF and the MNPPS ( p's < 0.05). The MSD underwent a quadratic increase ( p < 0.05). The spike shape measures had greater mean magnitudes and exhibited greater rates of changes across force levels for the monopolar electrode configuration ( p's < 0.05). The monopolar electrode configuration was therefore more sensitive to changes in muscle activity with increases in isometric force. This is an important consideration because the rate at which muscle electrical activity develops into a full interference pattern is an important qualitative and quantitative diagnostic measure.

Experimental and modelling investigation of surface EMG spike analysis

A pattern classification method based on five measures extracted from the surface electromyographic (sEMG) signal is used to provide a unique characterization of the interference pattern for different motor unit behaviours. This study investigated the sensitivity of the five sEMG measures during the force gradation process. Tissue and electrode filtering effects were further evaluated using a sEMG model. Subjects ( N = 8) performed isometric elbow flexion contractions from 0 to 100% MVC. The sEMG signals from the biceps brachii were recorded simultaneously with force. The basic building block of the sEMG model was the detection of single fibre action potentials (SFAPs) through a homogeneous, equivalent isotropic, infinite volume conduction medium. The SFAPs were summed to generate single motor unit action potentials. The physiologic properties from a well-known muscle model and motor unit recruitment and firing rate schemes were combined to generate synthetic sEMG signals. The following pattern classification measures were calculated: mean spike amplitude, mean spike frequency, mean spike slope, mean spike duration, and the mean number of peaks per spike. Root-mean-square amplitude and mean power frequency were also calculated. Taken together, the experimental data and modelling analysis showed that below 50% MVC, the pattern classification measures were more sensitive to changes in force than traditional time and frequency measures. However, there are additional limitations associated with electrode distance from the source that must be explored further. Future experimental work should ensure that the inter-electrode distance is no greater than 1 cm to mitigate the effects of tissue filtering.

Differences in EMG spike shape between individuals with and without non-specific arm pain

The purpose of this study was to determine whether spike shape analysis of surface electromyographic (SEMG) activity is a useful tool to study muscle disorders. This study investigated SEMG spike shape parameters at low levels of contraction and changes in SEMG spike shape across different levels of isometric wrist extension contractions in individuals with non-specific arm pain (NSAP), asymptomatic subjects deemed at-risk for repetitive strain injury, and asymptomatic control subjects. Twenty-two asymptomatic control subjects, 8 at-risk subjects, and 16 subjects with NSAP participated. Bipolar SEMG data were recorded from the ECRB muscle during isometric wrist extension contractions at 10, 20, 30, 40, 50, 60, and 70% of maximum voluntary contraction (MVC) force performed in a randomized order. Five criterion measures: mean spike amplitude (MSA), mean spike duration (MSD), mean spike slope (MSS), mean spike frequency (MSF), and mean number of peaks per spike (MNPPS) were computed from each SEMG signal. A one-way analysis of covariance (ANCOVA) of the spike shape parameters computed from the 10% MVC data, with group as a main effect and age as a covariate, revealed a significant group by age interaction for MSA, and significant group main effects for MSS and MNPPS, where the NSAP group had lower MSS and lower MNPPS than the control subjects. An ANCOVA including group as a main effect and contraction level and age as covariates revealed that all three groups showed predictable changes in the spike shape analysis criterion measures over increasing contraction force levels, where motor unit recruitment and rate coding appear to be the primary mechanisms for increasing force output of the muscle. Significant interactions between group and contraction level were observed for MSD, MSA, MSS, and MNPPS. The NSAP group presented with differences in how the spike shape measures change with increasing contraction level that may be indicative of myogenic changes, a result that is consistent with previous quantitative EMG findings. This work provides evidence that NSAP involves myogenic changes in the ECRB muscle and that spike shape analysis may be a valuable non-invasive tool in the evaluation of neuromuscular disorders.

Colic motor complex of the cecum and proximal loop of the ascending colon observed in an experimental cow with large intestinal obstruction.

Myoelectric activity of the cecum and proximal loop of the ascending colon (PLAC) and the effect of xylazine on motility of this intestinal segment in an experimental cow with large intestinal obstruction are described and compared with the normal motility pattern. During obstruction, three major observations were made in the prestenotic area. (i) Mean spike duration, overall duration of spiking activity (expressed as percentage of total recording time), number of spikes propagated from the cecum towards the obstruction site, and velocity of propagated spikes were substantially increased. (ii) The spike frequency was in the physiologic range. (iii) A single injection of xylazine, administered intravenously at a dose of 0.05 mg/kg markedly reduced the mean spike duration, the overall spiking activity, and the number of propagated spike sequences, and abolished signs of abdominal discomfort. Our data indicate that obstruction of the bovine colon causes a similar pattern of prestenotic hypermotility (colic motor complex) as described for the small intestine of the horse. Xylazine may be a suitable drug to disrupt prestenotic hypermotility and alleviate abdominal discomfort during proximal colonic obstruction in cattle.

Frequency analysis and duration of motor unit potentials: reliability and diagnostic usefulness

We studied the correlation, reliability and diagnostic usefulness of different time and frequency parameters of motor unit potentials (MUPs). Most frequency parameters were redundant because of high correlation with conventional MUP parameters. Variable selection algorithms for discriminant analysis indicated that center frequency (CENTFR) and spike duration (SPD) improved the discrimination between MUPs from normal, myopathic and neuropathic muscles. This was corroborated by univariate statistical tests comparing mean MUP duration (DUR), mean CENTFR and mean SPD of pathological muscles with those of normal muscles. One-sided tests for increased mean SPD improved the sensitivity for neurogenic changes and one-sided tests for reduced mean CENTFR improved the sensitivity for myopathic changes. The rate of false positive results did not increase by these additional tests. The retest reliability of CENTFR was superior to that of DUR. CENTFR and SPD are recommendable new parameters for quantitative MUP analysis based either on multi- or univariate statistics.

Barium ions induce prolonged plateau depolarizations in neurosecretory neurones of the adult rat supraoptic nucleus.

The occurrence and ionic basis of prolonged plateau depolarizations were studied during intracellular recordings obtained from thirty-nine supraoptic nucleus (s.o.n.) neurosecretory neurones in perfused explants of rat hypothalamus. Replacement of Ca2+ by Ba2+ in the perfusion media enhanced the shoulder on the repolarization phase of the action potentials in all of eleven cells tested. In Ba2+, spike durations increased as the holding membrane potential was made more positive, resulting in plateaux lasting up to 100 s. These plateaux were characterized by a sustained but slowly decaying absolute potential near 0 mV from which there appeared frequent spontaneous hyperpolarizing transients. A membrane resistance decrease of more than 50% was observed at the onset of a plateau, with gradual restoration during the plateau. Injection of Cs+ into twenty-one cells abolished the spike frequency adaptation and after-hyperpolarization associated with current-evoked bursts of action potentials. Mean spike duration after Cs+ injection increased from 2.5 +/- 0.3 ms to 68 +/- 9 ms (S.E. of mean). Addition of 4-5 mM-tetraethylammonium (TEA) to the perfusion media further increased the spike duration of nine Cs+-injected cells to 320 +/- 70 ms. No further increase could be obtained by doubling the concentration of TEA and/or by the addition of 0.2-0.5 mM-4-aminopyridine to the media. Although spike duration was greatly prolonged during such extensive blockade of K+ channels, plateau potentials lasting for longer than 1 s were observed only when Ba2+ was eventually added to the perfusion media. The special property of Ba2+ that leads to the formation of plateau potentials in s.o.n. neurones is therefore not restricted to its ability to reduce K+ conductances but may reside in its reduced effectiveness as a mediator of Ca2+-dependent inactivation of Ca2+ channels. Injection of Cs+ into s.o.n. neurones increased the slope of their current-voltage relationship below -60 mV from 148 +/- 15 to 257 +/- 41 M omega (S.E. of mean) and eliminated the outward rectification present at potentials above -60 mV. K+ currents are presumably active near the resting potential of these cells. Addition of Ba2+ to the perfusion media revealed a Cd2+-sensitive inward rectification above but not below ca. -55 mV. A slowly inactivating Ba2+ current is therefore carried through Ca2+ channels at potentials above -55 mV.(ABSTRACT TRUNCATED AT 400 WORDS)

Some properties of antidromically activated units in the paraventricular nucleus of the hypothalamus

The electrical activity of neurons in the paraventricular nucleus (PV) of the hypothalamus which project to the neural lobe was studied by recording extracellular single unit potentials excited by stimulation of the neural lobe. The action potentials were considered antidromic because they showed stable latencies, reliably followed short trains of high frequency stimulation at 100/sec or more, and could be blocked by orthodromic collision. The waveform of the antidromic action potentials was diphasic, positive-negative. The mean spike duration was 1.2 msec and the overall action potential including its longer lasting negativity was 2.7 msec. The majority of the units showed an inflection on the positive potential which could be enhanced by high frequency stimulation and was equated with the AB inflection described for other neurons. The B potential was labile, occasionally failing with single shock stimulation, and could be eliminated by two shocks given at a critical interval. An inflection on the rising part of the negative potential was also a feature of many of the PV units recorded. We conclude that the action potentials of PV neurosecretory cells in the mammalian hypothalamus exhibit no properties which cannot also be seen in nonsecretory neurons elsewhere in the central nervous system.

The differentiation of axonal and soma-dendritic spike activity.

Experiments were performed to examine the usefulness of mean spike duration measurements as a means of distinguishing between axonal and soma-dendritic activity recorded from the C.N.S. by glass insulated platinum microelectrodes. Units recorded from cat gracile and cuneate nuclei were separated into presynaptic and postsynaptic groups on the basis of: a) the maximum number of spikes evoked from a single electrical stimulus to the skin receptor area; b) the maximum frequency at which evoked spikes would follow every stimulus; c) the variability of latency at threshold stimulus intensity; d) the decrement of this variability upon increasing the intensity; e) the reduction of mean latency upon increasing stimulus intensity above threshold. Fifteen presynaptic units were recorded, all of which had short mean spike durations. Of the 41 postsynaptic units 5 exhibited short mean spike durations in the range associated with presynaptic units and were consequently classed as postsynaptic axons. The remaining postsynaptic units had long mean spike durations. On the basis of mean spike duration alone no presynaptic (i.e. primary afferent fibre) unit would have been erroneously classified as a postsynaptic (soma-dendritic) unit.