Kountouriotis Georgios K, Mole Callum D, Merat Natasha, Wilkie Richard M
Department of Psychology , Manchester Metropolitan University , Manchester M15 6GX , UK.
School of Psychology , University of Leeds , Leeds LS2 9JT , UK.
R Soc Open Sci. 2016 May 4;3(5):160096. doi: 10.1098/rsos.160096. eCollection 2016 May.
How do animals follow demarcated paths? Different species are sensitive to optic flow and one control solution is to maintain the balance of flow symmetry across visual fields; however, it is unclear whether animals are sensitive to changes in asymmetries when steering along curved paths. Flow asymmetries can alter the global properties of flow (i.e. flow speed) which may also influence steering control. We tested humans steering curved paths in a virtual environment. The scene was manipulated so that the ground plane to either side of the demarcated path produced larger or smaller asymmetries in optic flow. Independent of asymmetries and the locomotor speed, the scene properties were altered to produce either faster or slower globally averaged flow speeds. Results showed that rather than being influenced by changes in flow asymmetry, steering responded to global flow speed. We conclude that the human brain performs global averaging of flow speed from across the scene and uses this signal as an input for steering control. This finding is surprising since the demarcated path provided sufficient information to steer, whereas global flow speed (by itself) did not. To explain these findings, existing models of steering must be modified to include a new perceptual variable: namely global optic flow speed.
动物是如何沿着划定的路径行进的？不同物种对光流敏感，一种控制方法是保持视野中流对称性的平衡；然而，尚不清楚动物在沿着弯曲路径转向时是否对不对称性的变化敏感。流不对称性会改变流的全局属性（即流速），这也可能影响转向控制。我们测试了人类在虚拟环境中沿着弯曲路径转向的情况。对场景进行了操控，使得划定路径两侧的地面平面在光流中产生更大或更小的不对称性。不考虑不对称性和运动速度，改变场景属性以产生更快或更慢的全局平均流速。结果表明，转向并非受流不对称性变化的影响，而是对全局流速做出反应。我们得出结论，人类大脑对整个场景的流速进行全局平均，并将此信号用作转向控制的输入。这一发现令人惊讶，因为划定的路径提供了足够的转向信息，而全局流速（本身）却没有。为了解释这些发现，必须修改现有的转向模型，以纳入一个新的感知变量：即全局光流速度。
