老年人视觉方位、方向辨别能力衰退的神经机制研究

Degradation of visual functions during normal aging bring lots of trouble to the older. Therefore, researchers focused on its neural mechanism and made good progress. However, it remains unclear that the cellular mechanism underlying degradation of abilities of orientation and direction discrimination. Many researches suggested that degraded function of neurons in the older visual cortex might result in declines of visual perception. It is reasonable that degradation of neuronal function of orientation and direction discrimination in the old visual cortex would lead to the functional decline of the human. To verify the idea, we will focus on V1 (primary visual cortex) and MT (middle temporal visual cortex) of macaque using single-cell recording technology in vivo. 1) Collecting responses to orientation or direction of sinuous gratings and drawing orientation or direction tuning curve. 2) fitting the tuning curve with Von Mises equations and getting parameters of the equations. 3) calculating the slope of Von Mises equation and its maximum. The maximum slope is defined as neuronal discrimination. 4) calculating chernoff distance from Von Mises equation. 5) comparing neuronal discrimination and chernoff distance between that in the young and in the old. After achievement of the project, neural mechanism underlying the perceptual degradation of orientation and direction will be clarified. In addition, it will provide advice to age-related disease to some extent.

视觉系统的正常老化给老年人的生活带来巨大不便。因此，对其神经机制的研究称为国际上的研究热点并取得很大进展，但目前仍不清楚老年人方位、方向辨别能力下降的神经机制。研究发现老年视皮层细胞功能的衰退导致了老年人相关视觉功能的下降。因此可推测老年视皮层细胞/细胞群的方位、方向辨别力的下降导致了老年人方位、方向辨别能力的下降。为验证该想法，本顶目拟以猕猴的初级视皮层和中颞视区细胞为研究对象，使用在体单细胞记录技术采集细胞对正弦光栅方位、方向的调谐反应，使用VonMises方程对调谐反应进行拟合。求导取极值获得细胞的方位、方向辨别力，再用Chernoff算法计算细胞群的切尔诺夫距。比较青老年视皮层细胞的方位、方向辨别力和细胞群的切尔诺夫距差异，探明老年视皮层细胞/细胞群的方位、方向辨别力的衰退情况。本项目的完成可以初步阐明老年人方位、方向辨别能力下降的神经机制，并为有关老年病的治疗提供一定的指导意义。

视觉系统的正常老化给老年人的生活带来巨大不便。因此，对其神经机制的研究称为国际上的研究热点并取得很大进展，但目前仍不清楚老年人方位、方向辨别能力下降的神经机制。本顶目以猕猴的初级视皮层和中颞视区细胞为研究对象，使用在体单细胞记录技术采集细胞对正弦光栅方位、方向的调谐反应，使用VonMises方程对调谐反应进行拟合。求导取极值获得细胞的方位、方向辨别力，再用Chernoff算法计算细胞群的切诺夫距（Chernoff distance）。比较青老年视皮层细胞的方位、方向辨别力和细胞群的切诺夫距差异，发现：1）与青年猕猴相比，老年猕猴V1区细胞方位方向调谐曲线的Slopemax、MT细胞的方向调谐曲线的Slopemax显著性降低。2）分析细胞群的切诺夫信息量，发现V1区、MT区细胞群的切诺夫信息量显著性降低。这些结果表明老年猕猴方位方向辨别能力在细胞水平，和细胞群水平都发生了衰退，初步阐明老年人方位、方向辨别能力下降的神经机制，并为有关老年病的治疗提供一定的指导意义。