A modified method of estimating phase resetting of rhythmical movement

A computer-based method of estimating resetting index is presented which was successfully applied to a study of resetting of human voluntary rhythmical movement. Peaks were detected before and after the stimulus (magnetic cortical stimulation) from position records and the phase of stimulation and the phase change induced by the stimulus estimated. The phase change versus phase of stimulation relationship was rotated until the best linear fit was obtained: the gradient of this relationship is the resetting index. The calculation of resetting index was thus independent of the initial assignment of reference phase. A constant, the null phase, was derived from the best linear fit and indicates the phase to which the original waveform is being reset by the stimulus. Statistical tests of significance and linearity of the final relationship are also described.