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 C/s. The visual surround consisted of small red squares on a dark background and was presented in four different size/eccentricity conditions: central (approximately 15 degrees C - 60 degrees C), peripheral (approximately 60 degrees C-110 degrees C), full-field (15 degrees C-110 degrees C), 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.