Effect of sampling frequencies on the velocity of slow and fast phases of nystagmus.

A computer analysis of slow and fast phase of velocity of nystagmus is presented. Several methodological factors are known to affect the computation of velocities, such as sampling frequencies, cutoff frequencies of the differentiation method, and resolution in bits of analog-digital conversion. A simulated signal without noise was first applied in nystagmus data in order to study maximum velocities at the theoretical level. Electro-oculographic postrotational nystagmus movements were then examined to test theoretical results. It was shown that the sampling frequency ought to be 400 Hz at least, the cutoff frequency about 70 Hz, and the resolution of analog-digital conversion 12 bits or higher.