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Masahiko Fujita, Akihiro Amagai; Position-dependent gain adaptation of human horizontal saccades using the double step paradigm. Journal of Vision 2002;2(7):177. doi: 10.1167/2.7.177.
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© ARVO (1962-2015); The Authors (2016-present)
The visually guided (V-) and memory-guided (M-) saccades acquire different gains (primary saccade amplitude/target displacement) in the same horizontal direction simultaneously, after short-term adaptation using the intrasaccadic target step paradigm. Present study investigates whether the horizontal (vertical) saccade may reach different gains adaptively in the same horizontal (vertical) direction at different vertical (horizontal) directions.
Four subjects participated. In a dimly lit room, the subject traced a small light spot on a screen. We investigated the V-saccade and the M-saccade, separately. Target was displaced 4, 8, or 12° left or right to the fixation along the horizontal line. After 60 test trials, 60 adaptive trials were made along the horizontal line at the +5° level (up), where the target stepped forward during primary saccades to the adaptive direction by 30% of the initial step, thus inducing gain increasing adaptation. Then, 60 adaptive trials were made along the horizontal line at the −5° level (down), where the target stepped back by 50% of the initial step, thus inducing gain decreasing adaptation. These two procedures were repeated five times. Finally, 60 test trials were made at 5, 2.5, 0, −2.5, and −5°, respectively. The same experimental procedures were applied rotating the target displacement by 90° CCW from horizontal to vertical directions with the same target eccentricity.
The V-saccades showed little gain increasing at 5° but clear gain decreasing at −5°, while the M-saccades showed clear gain increasing at 5° and clear decreasing at −5°. Gains at the middle levels took middle values of the gains at 5° and −5°. Selective but mutually interfering adaptations of the horizontal (vertical) saccades in the same direction at different vertical (horizontal) levels were confirmed.
Generally, the gain adaptation in all directions may depend on the initial eye position.
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