Abstract
In this investigation of the interactions between the optokinetic and vestibular systems, a pendular optokinetic nystagmus (P-OKN) test was carried out on 34 normal subjects and compared with the pendular rotation tests (VOR and VVOR tests) and OKN tests used previously.
The subjects sat in a pendular sinusoidal rotating chair in an optokinetic drum, which provided pendular sinusoidal optokinetic stimulation. The optokinetic stimuli were at an amplitude of 120 degrees (total amplitude of 240 degrees) at frequencies of both 0.05Hz and 0.1Hz. With this stimulation there was no response decline phenomenon. The VVOR is considered to be the result of a synergistic interaction of the VOR and OKN. In our investigations the contribution from the vestibular system was 7 per cent with 0.1Hz frequency rotation. However, with 0.05Hz frequency rotation the contribution was very small. The gain of P-OKN, with slow phase velocity as a measure, was higher than that of OKN during linear acceleration and approximately equal to that of OKN induced by constant velocity stimuli.
The P-OKN test is a simple and useful test of the function of the oculomotor system, so it may become a screening test for central nervous system disorders.
