Motion coherence thresholds in infants - different tasks identify at least two distinct motion systems
Motion coherence thresholds in infants - different tasks identify at least two distinct motion systems
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DOI：
10.1016/s0042-6989(03)00077-4
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发表时间：
2003-05-01
期刊：
影响因子：
1.8
通讯作者：
Wattam-Bell, J
中科院分区：
文献类型：
--
作者：
Mason, AJS;Braddick, OJ;Wattam-Bell, J
视动性眼球震颤（OKN）从出生起就可以表现出来，但行为辨别任务（例如习惯和优先注视）直到几周大后才显示出对运动方向的任何敏感性。这项研究使用非常相似的刺激，比较了 6 至 27 周龄婴儿的 OKN 运动方向的一致性阈值和优先观看反应。婴儿接受了两个随机点运动显示器的测试，一个是用于 OKN 响应的移动点的均匀区域，另一个是通过不同的运动方向在一侧分割区域的显示器，用于优先观看响应。每个响应的一致性阈值通过阶梯法确定。对于 OKN 响应，平均一致性阈值在 20% 到 25% 之间，在整个年龄范围内 OKN 表现没有显着改善。优先查找阈值明显高于 OKN 阈值。优先观看阈值随着年龄的增长而显着改善，但在整个测试的年龄范围内仍然高于 OKN 阈值。改变方向反转频率和刺激区域的实验表明，这些差异不仅仅是优先观看刺激的空间和时间不均匀性的结果。我们发现 OKN 和优先观看反应的敏感性水平和年龄趋势的差异表明，这两种反应涉及不同的方向机制。我们讨论了这样一种可能性：在婴儿早期，OKN 和优先寻找分别反映了皮质下和皮质定向机制的表现。 (C) 2003 Elsevier Science Ltd. 保留所有权利。
Optokinetic nystagmus (OKN) can be demonstrated from birth, but behavioural discrimination tasks such as habituation and preferential looking do not reveal any sensitivity to motion direction until a few weeks of age. This study compared coherence threshold for motion direction for OKN and preferential looking responses using closely comparable stimuli, in infants between 6 and 27 weeks of age. Infants were tested with two random dot motion displays, a uniform area of moving dots for OKN responses and a display in which a region was segmented on one side by differential motion direction for preferential looking responses. Coherence thresholds for each response were determined by a staircase method. For OKN responses, mean coherence thresholds were between 20% and 25%, with no significant improvement in OKN performance throughout the age range. Preferential looking thresholds were significantly higher than OKN thresholds. Preferential looking thresholds improved significantly with age, but remained higher than OKN thresholds throughout the age range tested. Experiments varying direction reversal frequency and stimulus area indicated that these differences were not simply a consequence of the spatial and temporal non-uniformity of the preferential looking stimulus.The differences in sensitivity levels and age trends for OKN and preferential looking responses we have found suggest that different directional mechanisms are involved in the two responses. We discuss the possibility that, in early infancy, OKN and preferential looking reflect the performance of subcortical and cortical directional mechanisms respectively. (C) 2003 Elsevier Science Ltd. All rights reserved.