An extended difference of coherence test for comparing and combining several independent coherence estimates: theory and application to the study of motor units and physiological tremor.

Recently there has been an increase in the use of spectral methods for the analysis of experimental data. These analytical methods allow the study of interactions between simultaneously recorded signals and are particularly suited to the study of systems displaying rhythmic behaviour. A useful parameter in this context is the coherence function which provides a bounded measure of linear association between two signals. In this report we introduce two new techniques for dealing with an arbitrary number of independent coherence estimates. The first technique provides a test to compare the coherence estimates for statistically significant differences. The second allows the original coherence estimates to be combined, or 'pooled' into a single representative estimate. These two measures, taken together, provide a powerful tool for characterising and summarising the correlations within data sets. Applications of the techniques are illustrated by analysing the interactions between single motor unit discharges and finger tremor, and between pairs of motor unit discharges in human subjects.

A comparison of methods of predicting maximum oxygen uptake.

The aim of this study was to compare the results from a Cooper walk run test, a multistage shuttle run test, and a submaximal cycle test with the direct measurement of maximum oxygen uptake on a treadmill. Three predictive tests of maximum oxygen uptake--linear extrapolation of heart rate of VO2 collected from a submaximal cycle ergometer test (predicted L/E), the Cooper 12 min walk, run test, and a multi-stage progressive shuttle run test (MST)--were performed by 22 young healthy males (mean(s.d.) age 22.1 (2.4) years; body mass 72.4(8.9kg)) and the values compared to those obtained by direct measurement on a maximal treadmill test. All of the subjects were regular exercisers. The mean(s.d.) from the various tests in ml.kg-1.min-1 were as follows: treadmill 60.1(8.0), Cooper 60.6(10.3), MST 55.6(8.0), and predictedL/E 52.0(8.4). The Cooper test had a correlation with the treadmill test of 0.92, while the MST and the predictedL/E had correlations of 0.86 and 0.76 respectively. Both the MST and predictedL/E showed systematic underprediction of the treadmill value. On average, the MST was 4.5 ml.kg-1.min-1 (s.e. 0.9) lower than the treadmill VO2max while the predictedL/E was 7.8 ml.kg-1. min-1 (s.e. 1.4) lower than the treadmill VO2max. These findings indicate that, for the population assessed, the Cooper walk run test is the best predictor of VO2max among the three tests.

Development of a live cell culture camelpox vaccine.

A Saudi isolate of camel orthopoxvirus was serially propagated on monolayers of camel kidney cell cultures. The attenuation of the 78th passage was tested in two susceptible camels. Two other susceptible camels were inoculated with vaccinia virus four times propagated in camel kidney cell cultures. The four inoculated camels showed no postinoculation clinical symptoms and formed neutralizing antibodies against both the camel orthopox and vaccinia viruses. No postchallenge clinical symptoms were observed in these four camels, while two non-inoculated contact control camels showed typical symptoms of generalized camelpox. These results indicated the safety and potency of the 78th passage of the Saudi isolate of camel orthopoxvirus (designated Jouf-78) to be used for production of live attenuated cell culture camelpox vaccine. The field testing of the vaccine was carried out on two farms using at least 10(3) TCID50 as a recommended field dose. None of the inoculated camels showed any postvaccination reaction and the serological tests showed seroconversion of many vaccinated field camels. The relationship between camel orthopoxvirus and vaccinia virus as well as the advantages of the live attenuated camelpox vaccine are discussed.

A framework for the analysis of neuronal networks.

The object of this work is to consider the application of some methods of spike train analysis that are not widely known, and are concerned with the description of the interaction between spike trains and the determination of causal connections between them. The notation and terminology follow conventions established in the statistical literature. The examples given are based on in-continuity recordings of the spontaneous activity of single Ia afferents from the soleus muscle and single motor units from the same muscle. Cumulant densities are shown to be simple extensions of the traditional cross-correlation methods, and are useful in characterizing the pattern of activity in one spike train that influences that in another, and to reveal interactions between spike trains that would not be apparent from the correlation histogram alone. Parameters based on the Fourier transforms of the spike trains are shown to be useful in determining timing relations between them, and in inferring patterns of connectivity not possible by correlation methods alone.