Human optokinetic responses under quasi-open and closed loop conditions.

The human optokinetic response to a horizontally moving stripped pattern surrounding the subject was investigated under quasi-open and closed loop conditions. Open loop conditions were produced by the addition of an external signal from measured slow phase eye velocity to stripe velocity. A comparison of open and closed loop responses to step and sinusoidal changes of stripe velocity indicates that the central nervous system controlling slow phase optokinetic following can be described as a simple first order lag (Ka/(s + a)) where K is 4.7 and the time constant, 1/a, is 1.25 s.