Yang Y, Liang Z, Li G, Wang Y, Zhou Y, Leventhal A G
Vision Research Laboratory, School of Life Science, University of Science and Technology of China, Huangshan Road, Hefei, Anhui 230027 230027, PR China.
Neuroscience. 2008 Oct 15;156(3):748-57. doi: 10.1016/j.neuroscience.2008.08.007. Epub 2008 Aug 12.
In the present study we studied the effects of aging on the coding of contrast in area V1 (primary visual cortex) and MT (middle temporal visual area) of the macaque monkey using single-neuron in vivo electrophysiology. Our results show that both MT and V1 neurons in old monkeys are less sensitive to contrast than those in young monkeys. Generally, contrast sensitivity is affected by aging more severely in MT cells than in V1 cells. Specifically, MT cells were affected more severely than motion direction selective V1 cells. Particularly, we found that MT neurons in old monkeys exhibited enhanced maximum visual responses, higher levels of spontaneous activity and decreased signal-to-noise ratios. In addition, we also found age-related changes in neuronal adaptation to visual motion in MT. Compared with young animals, the contrast gain of MT neurons in old monkeys is less affected, but the response gain by adaptation of MT neurons is more affected. Our results suggest that there may be an anomalous visual processing in both the magnocellular and parvocellular pathways. The neural changes described here are consistent with an age-related degeneration of intracortical inhibition and could underlie some deficits in visual function during normal aging.
在本研究中，我们利用猕猴活体单神经元电生理学，研究了衰老对猕猴V1区（初级视觉皮层）和MT区（颞中区视觉区域）对比度编码的影响。我们的结果表明，老年猕猴的MT区和V1区神经元对对比度的敏感度均低于幼年猕猴。一般来说，MT区细胞的对比度敏感度受衰老的影响比V1区细胞更严重。具体而言，MT区细胞比V1区方向选择性运动细胞受影响更严重。特别地，我们发现老年猕猴的MT区神经元表现出增强的最大视觉反应、更高水平的自发活动以及降低的信噪比。此外，我们还发现MT区神经元对视觉运动的神经适应性存在与年龄相关的变化。与幼年动物相比，老年猕猴MT区神经元的对比度增益受影响较小，但MT区神经元适应性反应增益受影响更大。我们的结果表明，在大细胞和小细胞通路中可能存在异常的视觉处理。这里描述的神经变化与皮质内抑制的年龄相关退化一致，并且可能是正常衰老过程中一些视觉功能缺陷的基础。
