Decreased contrast sensitivity of visual cortical cells to visual stimuli accompanies a reduction of intracortical inhibition in old cats

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 V1（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 V1 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,V1 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 V1 neurons accompanied a reduction of intracortical inhibition during senescence.

一日龄粘虫不同时长吊飞对生殖及寿命的影响

【目的】本研究旨在阐明羽化后1日龄粘虫Mythimna separata(Walker)的飞行潜力以及飞行对成虫生殖和寿命的影响,从而进一步解析粘虫的迁飞行为特征。【方法】利用室内昆虫飞行磨计算机数据采集系统,研究了羽化后1日龄粘虫吊飞6、9和12 h的飞行能力差异,以及不同时长吊飞后粘虫的生殖参数和成虫寿命的变化情况。【结果】结果表明,1日龄雌雄蛾均具有一定的飞行能力,但当吊飞时间超过9 h之后,成虫的飞行时间、距离和速度均不再显著上升。除吊飞12 h成虫的飞行速度外,其它处理雌雄蛾的飞行能力之间无显著差异。羽化后1日龄不同时长吊飞对粘虫的生殖均有显著的促进作用,但随着吊飞时间的延长,这种促进作用显著降低。6、9和12 h吊飞处理均导致成虫产卵前期显著缩短,但仅吊飞6和9 h成虫的产卵量和产卵历期显著高于对照。吊飞12 h成虫的产卵量和产卵历期则显著低于吊飞6和9 h的成虫,并和对照差异不显著。吊飞12 h后,雌雄成虫寿命均显著缩短。【结论】羽化后1日龄飞行显著促进粘虫的生殖,但随着飞行时间的延长,飞行对生殖的促进效应显著减弱。