Automatic onset detection of rapid voluntary contractions in tremor patients

If a rapid voluntary contraction is superimposed to an on-going periodic muscle activity as occuring in tremor patients, an exact detection of its onset to determine reaction time is difficult, because separation of both signal components is ambiguous sometimes. This paper describes a method which allows automatic onset detection by computer program. This estimates the future time course of the periodic contraction from its history for every signal sample, and onset detection is taken when the deviation from the expected time course exceeds a threshold criterium. Problems arising from the instationarity of the tremor as well as from the variation of the voluntary contractions are discussed.