THE EFFECTS OF VISUAL SURROUND ECCENTRICITY AND SIZE ON MANUAL AND POSTURAL CONTROL

This study investigated how the size and eccentricity of a moving visual surround influence manual and postural control, Twelve subjects performed a manual control task (keep an unstable central display level) and a postural control task (maintain an upright stance) while viewing a visual surround that rotated continuously at 25 degrees/s. The visual surround consisted of small red squares on a dark background and was presented in four different size/eccentricity conditions: central (similar to 15 degrees-60 degrees), peripheral (similar to 60 degrees-110 degrees), full-field (15 degrees-110 degrees), or central-peripheral conflict, The results showed that manual control biases in the direction of surround motion are strongly influenced by central-field as well as peripheral-field motion, whereas postural control biases are determined primarily by motion in the peripheral visual field.