Zhou Jun, Shi Xia-Ming, Peng Qing-Song, Hua Guo-Peng, Hua Tian-Miao
School of Life Science, Anhui Normal University, Wuhu 241000, China.
Dongwuxue Yanjiu. 2011 Oct;32(5):533-9. doi: 10.3724/SP.J.1141.2011.05533.
Psychophysical experiments on human and animal subjects have proven that aged individuals show significantly reduced visual contrast sensitivity compared with young adults. To uncover the possible neural mechanisms, we used extracellular single-unit recording techniques to examine the response of V(1) (primary visual cortex) neurons as a function of visual stimulus contrast in both old and young adult cats (Felis catus). The mean contrast sensitivity of V(1) neurons to visual stimuli in old cats decreased significantly relative to young adult cats, consistent with findings reported in old primates. These results indicate that aging can affect contrast sensitivity of visual cortical cells in both primate and non-primate mammalian animals, and might contribute to the reduction of perceptual visual contrast sensitivity in aged individuals. Further, V(1) cells of old cats exhibited increased responsiveness, decreased signal-to-noise ratio, and enlarged receptive field (RF) size compared with that of young adult cats, which indicated that decreased contrast sensitivity of V(1) neurons accompanied a reduction of intracortical inhibition during senescence.
针对人类和动物受试者的心理物理学实验已经证明，与年轻成年人相比，老年人的视觉对比敏感度显著降低。为了揭示可能的神经机制，我们使用细胞外单单元记录技术，研究了老年和年轻成年猫（家猫）初级视觉皮层（V1）神经元对视觉刺激对比度的反应。与年轻成年猫相比，老年猫V1神经元对视觉刺激的平均对比敏感度显著降低，这与老年灵长类动物的研究结果一致。这些结果表明，衰老会影响灵长类和非灵长类哺乳动物视觉皮层细胞的对比敏感度，可能是导致老年人视觉感知对比敏感度下降的原因。此外，与年轻成年猫相比，老年猫的V1细胞反应性增加、信噪比降低、感受野（RF）尺寸增大，这表明V1神经元对比敏感度降低伴随着衰老过程中皮层内抑制作用的减弱。
