Joshi Mahesh Raj, Falkenberg Helle K
Department of Optometry and Visual Science, Buskerud and Vestfold University College, Frogsvei 41, Kongsberg 3611, Norway.
Vision Res. 2015 May;110(Pt A):68-75. doi: 10.1016/j.visres.2015.03.006. Epub 2015 Mar 20.
The development of sensitivity to radial optic flow discrimination was investigated by measuring motion coherence thresholds (MCTs) in school-aged children at two speeds. A total of 119 child observers aged 6-16years and 24 young adult observers (23.66+/-2.74years) participated. In a 2AFC task observers identified the direction of motion of a 5° radial (expanding vs. contracting) optic flow pattern containing 100 dots with 75% Michelson contrast moving at 1.6°/s and 5.5°/s and. The direction of each dot was drawn from a Gaussian distribution whose standard deviation was either low (similar directions) or high (different directions). Adult observers also identified the direction of motion for translational (rightward vs. leftward) and rotational (clockwise vs. anticlockwise) patterns. Motion coherence thresholds to radial optic flow improved gradually with age (linear regression, p<0.05), with different rates of development at the two speeds. Even at 16years MCTs were higher than that for adults (independent t-tests, p<0.05). Both children and adults had higher sensitivity at 5.5°/s compared to 1.6°/s (paired t-tests, p<0.05). Sensitivity to radial optic flow is still immature at 16years of age, indicating late maturation of higher cortical areas. Differences in sensitivity and rate of development of radial optic flow at the different speeds, suggest that different motion processing mechanisms are involved in processing slow and fast speeds.
通过测量学龄儿童在两种速度下的运动相干阈值（MCTs），研究了对径向视流辨别敏感性的发展情况。共有119名6至16岁的儿童观察者和24名年轻成人观察者（23.66±2.74岁）参与。在一个二选一迫选任务中，观察者要识别一个包含100个点、对比度为75%的迈克尔逊对比度、以1.6°/秒和5.5°/秒速度移动的5°径向（扩张与收缩）视流模式的运动方向。每个点的方向从高斯分布中抽取，其标准差要么低（相似方向）要么高（不同方向）。成人观察者还要识别平移（向右与向左）和旋转（顺时针与逆时针）模式的运动方向。对径向视流的运动相干阈值随年龄逐渐提高（线性回归，p<0.05），在两种速度下发展速率不同。即使在16岁时，MCTs仍高于成人（独立t检验，p<0.05）。儿童和成人在5.5°/秒时的敏感性都高于1.6°/秒（配对t检验，p<0.05）。16岁时对径向视流的敏感性仍不成熟，表明高级皮层区域成熟较晚。不同速度下径向视流敏感性和发展速率的差异，表明不同的运动处理机制参与了慢速和快速运动的处理。
