Reduction in Direction Discrimination With Age and Slow Speed Is Due to Both Increased Internal Noise and Reduced Sampling Efficiency
Reduction in Direction Discrimination With Age and Slow Speed Is Due to Both Increased Internal Noise and Reduced Sampling Efficiency
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DOI：
10.1167/iovs.13-12005
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发表时间：
2013-08-01
影响因子：
4.4
通讯作者：
Falkenberg, Helle K.
中科院分区：
文献类型：
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作者：
Bogfjellmo, Lotte-Guri;Bex, Peter J.;Falkenberg, Helle K.
目的.对移动结构的敏感性随着年龄的增长而降低，并且可能选择性地损害慢速。这种损失可能是由运动传感器响应中的内部噪声升高或运动响应集成效率降低引起的。我们采用等效噪声范式来分析作为正常年龄的函数的慢速和快速运动的感知。共有70名观察员（20-89岁）确定了全球运动的方向，在一个两个选择的强迫选择任务。在中心8度光圈中，100个10%迈克尔逊对比度的点以1.6或5.5度/秒移动。每个点的方向是从高斯分布，其平均值和SD是自适应变化的。内部噪声和采样效率估计方向辨别阈值作为外部方向噪声，速度和年龄的函数。在所有年龄段，慢速运动的方向敏感性都明显较差（配对t检验，P < 0.05），并且每年下降约2%（线性回归，P < 0.01）。这种老化缺陷是由于内部噪声（5.5度/秒）和采样效率（1.6度/秒）的显著变化（线性回归，P < 0.05）。随着年龄的增长，运动灵敏度会下降，这是由于方向传感器响应中的内部噪声增加以及有助于全局决策的响应减少。每种速度下的进展速率差异表明，运动是由调整到不同速度的独立系统处理的，并且慢速通道可能更容易受到正常年龄相关变化的影响。
PURPOSE. Sensitivity to moving structure decreases with age and slow speeds may be selectively impaired. This loss could be caused by elevated internal noise in the responses of motion sensors or a reduction in the efficiency with which motion responses are integrated. We adapt an equivalent noise paradigm to analyze the perception of slow and fast speed motion as a function of normal aging.METHODS. A total of 70 observers (20-89 years) identified the direction of global motion in a two-alternative forced choice task. In a central 8 degrees aperture, 100 dots of 10% Michelson contrast were moving at 1.6 or 5.5 degrees/s. The direction of each dot was drawn from a Gaussian distribution whose mean and SD were adaptively changed. Internal noise and sampling efficiency were estimated from direction discrimination thresholds as a function of external direction noise, speed, and age.RESULTS. Direction sensitivity was significantly worse for slow speeds at all ages (paired t-test, P < 0.05) and decreased approximately 2% per year (linear regressions, P < 0.01). This aging deficit was due to significant changes in internal noise (5.5 degrees/s) and sampling efficiency (1.6 degrees/s) (linear regression, P < 0.05).CONCLUSIONS. There is motion sensitivity loss with age that arises from an increase in internal noise in the responses of directional sensors and a decrease in responses that contribute to the global decision. Differences in the rates of progression at each speed indicate that motion is processed by independent systems tuned to different speeds, and that the channel for slow speed may be more vulnerable to normal age-related changes.