Laboratory of Neuromotor Physiology, IRCCS Santa Lucia Foundation, Via Ardeatina 306, 00179 Rome, Italy.
Exp Brain Res. 2013 Sep;229(4):579-86. doi: 10.1007/s00221-013-3620-3. Epub 2013 Jun 27.
By simulating self-motion on a virtual rollercoaster, we investigated whether acceleration cued by the optic flow affected the estimate of time-to-passage (TTP) to a target. In particular, we studied the role of a visual acceleration (1 g = 9.8 m/s(2)) simulating the effects of gravity in the scene, by manipulating motion law (accelerated or decelerated at 1 g, constant speed) and motion orientation (vertical, horizontal). Thus, 1-g-accelerated motion in the downward direction or decelerated motion in the upward direction was congruent with the effects of visual gravity. We found that acceleration (positive or negative) is taken into account but is overestimated in module in the calculation of TTP, independently of orientation. In addition, participants signaled TTP earlier when the rollercoaster accelerated downward at 1 g (as during free fall), with respect to when the same acceleration occurred along the horizontal orientation. This time shift indicates an influence of the orientation relative to visual gravity on response timing that could be attributed to the anticipation of the effects of visual gravity on self-motion along the vertical, but not the horizontal orientation. Finally, precision in TTP estimates was higher during vertical fall than when traveling at constant speed along the vertical orientation, consistent with a higher noise in TTP estimates when the motion violates gravity constraints.
通过在虚拟过山车中模拟自身运动，我们研究了光流引起的加速度是否会影响对目标通过时间（TTP）的估计。具体来说，我们通过操纵运动规律（以 1g 的加速度或减速度加速，匀速）和运动方向（垂直、水平）来研究视觉加速度（1g=9.8m/s²）模拟场景中重力影响的作用。因此，向下的 1g 加速运动或向上的减速运动与视觉重力的影响一致。我们发现，加速度（正或负）在计算 TTP 时被考虑在内，但在模块中被高估，而与方向无关。此外，当过山车以 1g 向下加速（如自由落体）时，参与者相对于在水平方向上发生相同加速度时更早地发出 TTP 信号。这种时间移位表明，相对于视觉重力的方向对响应时间有影响，这可能归因于对垂直方向上视觉重力对自身运动的影响的预期，但不是水平方向上的影响。最后，在垂直下落时，TTP 估计的精度比沿垂直方向以恒定速度行驶时更高，这与违反重力约束时 TTP 估计的噪声更高一致。
