Kunimitsu TAKAHARA^*, Katsunori OKAJIMA^* and Masanori TAKASE

Department of Applied Physics, National Defense Academy, 1-10-20 Hashirimizu, Yokosuka, Kanagawa 239-8686, Japan

(Received January 6, 2005; Accepted December 14, 2005)

We investigated whether an adaptation effect occurs in a virtual environment where an extent of retinal image motion caused by head rotation is modulated depending on the extent of the rotation. We defined the value “Gain”, as the ratio of “the angular velocity of retinal motion in the virtual environment” to “the angular velocity of head motion in the real environment”. Subjects rotated their heads in the adaptation phase in which one of three Gains (0.5, 1.0, and 1.5) was adapted; the phase lasted one period (3 min). Immediately afterwards, they adjusted the Gain to enable them to perceive a “stable environment” in the test phase. The results showed that adjusted Gains in the test phase tended to shift to the adaptation Gains. In addition, we tested whether the adaptation effect occurs in the somatic system and whether interocular transfer occurs, and found that the somatic system was not modulated by immersion in the conflicting environment but interocular transfer was observed. These results indicate that our visual stability system can adapt to such virtual environments within short minutes and that the adaptation effect occurs in our binocular visual system.

Key words: visual stability, recalibration, adaptation, head movement, visual motion, virtual reality

^*Present address: Graduate School of Environment and Information Sciences, Yokohama National University, 79-1 Tokiwadai, Hodogaya-ku, Yokohama 240-8501, Japan.