Quantification of individual variation and effects of aging in a speed of human visual information processing.

从随着年龄的增长视觉系统的能力下降的观点出发，研究了老年人观看运动图像、物体等短时间内呈现的刺激时，视觉信息处理速度的下降。在本研究中，我专注于感知的一部分，并在处理速度如何受到老化的影响方面，定量研究了个体的变化。在实验中，我测量了发光和彩色脉冲响应函数（IRF）的双脉冲方法的个体差异和老化效应。在彩色IRFs的测量中，我瞄准了S-锥，S-锥是在最接近紫外光的短波长区域具有灵敏度的感光器。对于S锥刺激，我测量了个体S锥混淆线。结果表明，在16.6 ~ 86.3岁年龄段，分别对70名（发光实验）和49名（色度实验）的观察者进行了发光和色度IRF的推导。我发现，在这个年龄范围内，随着年龄的增长，视觉反应的强度在发光反应中降低了49.5%，在色度反应中降低了44.2%。另一方面，基本上没有观察到响应速度的下降。然而，只有在发光IRFs的情况下，60%的60岁以上的观察者的反应功能变得更慢，没有抑制期。这表明，老化效应的补偿机制，即与年龄相关的信号强度的下降被补偿的总和时间的增加，只适用于发光信息的途径，而不是在彩色信息的。这反映了在目标和运动检测中，光信息是很重要的，而颜色信息对它们的要求不是很高。

From the viewpoint of deterioration of ability for visual system by aging, I took up the deterioration of visual information processing speed when elderly people watch stimuli presented in short duration like the case of watching moving images and objects. In this research, I focused on a perception part and investigated an individual variation quantitatively in terms of how the processing speed is affected by aging.In experiments, I measured individual variation and aging effects in luminous and chromatic impulse response functions (IRFs) by a double-pulse method. In measurement of the chromatic IRFs, I aimed at the S-cone that is the photoreceptor having sensitivity in short wavelength region closest to ultraviolet light. For the S-cone stimulation, I measured individual S-cone confusion line. I analyzed threshold data when two pulses were presented with different intervals and derived luminous and chromatic IRFs for each observer.As the results, on 70 (in the luminous experiment) and 49 observers (in the chromatic experiment) in 16.6 - 86.3 years old, I succeeded in derivation of luminous and chromatic IRFs. I found that the intensity of visual response was reduced in 49.5% in the luminous response and 44.2% in chromatic responses by aging in this age range. On the other hand, the decline of response speed was not basically observed. Only in the case of luminous IRFs, however, the response functions became slower and did not have an inhibitory phase in 60% of observers older than 60 years old. It suggests that the compensation mechanism of aging effect, in which the age-related decline of signal strength is compensated by increase of summation time, works only in pathways for luminous information but not in ones for chromatic information. It can reflect that luminous information is important in detections of object and motion but information of color is not very much needed for them.