EXTENDED REPORT Torsional optokinetic nystagmus: normal response characteristics
نویسندگان
چکیده
Background/aims: Few studies have investigated normal response characteristics of torsional optokinetic nystagmus (tOKN). The authors have investigated the effect of stimulus velocity and central/peripheral stimulation on tOKN. Methods: Torsional OKN was elicited using a sinusoidal grating rotating at velocities of 3 /̊s to 1000 /̊s in clockwise and anticlockwise directions. To investigate the effect of central stimulation, stimulus size was varied from 2.86 ̊ to 50.8 .̊ An artificial scotoma placed over a 50.8 ̊ stimulus was varied from 2.86 ̊ to 43.2 ̊ to investigate peripheral stimulation. Eight subjects participated in each experiment and torsional eye movements were recorded using video-oculography. The mean slow phase velocity (MSPV) and gain were calculated. Results: The maximum gain occurred in response to 8 /̊s stimulation. The MSPV increased up to a stimulus velocity of 200 /̊s achieving a maximum of 3 /̊s in both directions. MSPV was linearly correlated with the log of stimulus velocity. The smallest field size, rotating at 40 /̊s, evoked 10% of the gain elicited by the largest display. When the most peripheral stimulus was used, the gain was maintained at 50% of the gain evoked when the full display was used. Conclusions: A wide range of stimulus velocities can elicit tOKN and peripheral field stimulation contributes significantly to its response.
منابع مشابه
Torsional Optokinetic Nystagmus: Response Characteristics Measured in the Normal Population and Patients with Ocular Motor Disorders
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