Aging Affects Response Latency And Variability Of Cells In Different Visual Areas In Cats

During normal aging, visual abilities are impaired as a result. This kind of functional impairment can not be simply contributed to the changes in the optical system of eyes. Instead, more and more discoveries have proved that the degradation of visual nerve system should be responsible for this phenomenon. In different visual areas, the degradation of neuron characters is different. There is a hypothesis says that more advanced visual cortex hurt more seriously during aging, but it still needs further evidences to support. In this research, we use two important time characters, response latency and variability, to evaluate the degeneration of visual characters. Based on this research, we try to verify the hypothesis mentioned above and provide supports for the degradation of advanced visual functions.In this research, we compared visual response latency in LGN, V1, V2 and PMLS in old and young cats. We found that there is no significant change of the response latency in LGN between old cats and young cats. But in the other three areas, old cats exhibited significantly longer response latency than those in young cats. And this kind of prolongation was more significant in area with higher level in visual system. These findings suggested that aging would lengthen response latency in visual areas and more advanced areas were influenced more serious. What's more, the prolongation was passed on from one area to another one with higher level, and the damages were accumulating in visual pathway.To further investigate the influence of aging on response variability, we compared response variability in LGN, V1, V2 and PMLS in old and young cats. It showed that there was no significant change of the response variability in LGN between old and young cats. But in other three areas, response variability was influenced differently by aging. Response variability was enlarged in old cats and more advanced areas got more damages. It is known that response variability might affect latency in visual pathway. Therefore, we further studied the correlation between increased response variability and prolonged visual response latency. Our study showed that there was a strong correlation between these two factors, which indicated the close inner relationship between them.With the research mentioned above, we studied the influences of aging process on time response character of cells in different areas in the visual pathway. The result was that area with higher level in visual pathway exhibited more secure functional degradation, and this degeneration accumulated in the visual pathway gradually. This result provided supports for the hypothesis that more advanced visual cortex was influenced more seriously by aging, and also provided new evidences for the degradation of some visual functions related to time character during aging.