Interference between synchronous optokinetic nystagmus and vestibular nystagmus

This interference between vestibular nystagmus and optokinetic nystagmus was studied in healthy humans and in patients with lesions of the central or the peripheral vestibular system. The optokinetic system was able to depress vestibular impulses when the test conditions allowed stable fixation upon the optokinetic targets (synchronous OKN). With a slow target speed both systems contributed to the resultant nystagmus but no interaction between vestibular nystagmus and OKN took place. The vestibular nystagmus was independently superimposed on the OKN. In cases with an acute lesion of the vestibular system, stable fixation upon the optokinetic targets was not possible and only in these cases did the vestibular component dominate the response. It is concluded that a common integrator for vestibular and optokinetic nystagmus does not exist.