Propagation velocity measurement: autocorrelation technique applied to the electromyogram.

E Spinelli,J C Politti,M E Valentinuzzi,M Mayosky,C J Felice

doi:10.1007/bf02345151

Abstract

Muscle fibre conduction velocity is an important measurement in electrophysiology, both in the research laboratory and in clinical practice. It is usually measured by placing electrodes spaced at known distances and estimating the transit time of the action potential. The problem, common to all methods, is the estimation of this time delay. Several measurement procedures, in the time and frequency domains, have been proposed. Time-domain strategies usually require two acquisition channels, whereas some frequency-domain methods can be implemented using a single one. The method described operates in the time domain, making use of the autocorrelation function of the difference signal obtained from two needle electrodes and only one acquisition channel. Experimental results were obtained from the electromyogram of two biceps muscles (two adult male subjects, nine records each) under voluntary contraction, yielding an average of 3.58 m s(-1) (SD=0.04 m s(-1)) and 3.37m s(-1) (SD=0.03 m s(-1)), respectively. Several tests showed that the proposed method works properly with electromyogram records as short as 0.3 s.

Highlights

MEASUREMENTOF electrophysiological conduction velocity is based on the estimation of the time required for the action potential to traverse a known distance
In this paper, expr. 7, similar to the expression proposed by PARKERand SCOTT(1973), has been adopted for p(t), where Co, q, and c2 are constants that must be obtained from experimental data t ( q - Cot) e x p ( - c 2 t ) t ~> 0 p(t)= 0 t
An expression for the autocorrelation function ~ss(z) of S(t) for EMG signals was derived by PARKERand SCOTT (1973)

Summary

Introduction

MEASUREMENTOF electrophysiological conduction velocity is based on the estimation of the time required for the action potential to traverse a known distance. It was first Herman von Helmholtz (GEDDESand HOFF, 1968), in 1850, and, in about 1928, Erlanger and Gasser (ERLANGERand GASSER, 1937), both Nobel laureates, who accurately and very ingeniously measured conduction delays and velocities (in nerve). Some frequency-domain methods, on the other hand, allow the measurement of the time delay using a single acquisition channel These methods usually involve strong computational demands and require large numbers of data (PARKERet al., 1977; VICAR and PARKER,1988). The proposed method requires only one acquisition channel and preserves the characteristics of timedomain methods, such as low computational complexity and proper operation even with short data records

Proposed method

Application to muscular action potential propagation delays

Method

Validation of the method

Findings

Discussion