Analysis of human vestibulo-ocular reflex during active head movements.

The human vestibulo-ocular reflex (VOR) was investigated during active head movements utilizing spectral analysis techniques in order to extract phase and gain characteristics for the most natural stimulus conditions. Three different experimental conditions were examined: 1) head rotation in darkness to obtain data permitting a comparison with that mode of VOR analysis which has been mose frequently employed in the past; 2) head rotation while fixating a stationary target light in order to quantify natural compensatory eye movements; and 3) head rotation while fixating a target light which moved with the head as a fast method for the quantification of visuo-vestibular interaction. High frequency head rotation in darkness yielded gains not significantly different from unity-unlike previously reported results for passive rotation (Benson, 1970; Keller, 1978). Possible mechanisms which might explain these results are discussed.