A role of afferent activity in the maturation of thalamocortical connections of visual system

猫、猴等哺乳动物包括人类在内的视皮层神经元的双眼视觉反应性在出生后发育的关键期受到单眼视觉剥夺的影响，最著名的经验之一据推测，来自每只眼睛的传入神经相互竞争与皮层神经元的突触连接，使得来自被剥夺眼睛的较不活跃的传入神经无法保持连接，即，两种传入神经活动之间的平衡对于决定每种眼睛特异性通路的命运是重要的。2这种突触竞争假说已经得到小猫各种剥夺实验的支持。如果这样的竞争假说是有效的，那么增加输入从一只眼睛，而不是减少由于剥夺也应该改变皮层神经元的双眼反应。另外，剥夺引起的变化可能是由于“废用”减弱的反应性。然而，这一假设从未被用这样的单眼激活范式来检验。在本项目中，我们激活的视神经之一的行为小猫2天的电刺激，并发现，这种慢性，单眼激活引起的皮层神经元的视觉反应的眼优势的转变。

Binocular visual responsiveness of neurons in visual cortex of cats, monkeys and other mammals including humans can be changed by monocular visual deprivation in the critical period of postnatal development, one of the best-known examples of experience-dependent modification of brain function.It is hypothesized that afferents from each eye compete with one another for synaptic connections with cortical neurons so that less active afferents from the deprived eye fail to maintain the connections, i.e., balance between activities of both afferents is important to determine the fate of each eye-specific pathway.This synaptic competition hypothesis has been supported by various types of deprivation experiments in kittens. If such a competition hypothesis is valid, then an increase in inputs from one eye instead of decrease due to deprivation should also change binocular responsiveness of cortical neurons. Otherwise the deprivation-induced change might be due to "disuse" weakening of responsiveness.However, the hypothesis has never been tested with such a monocular activation paradigm. In the present project, we activated one of the optic nerves by electrical stimulation in behaving kittens for 2 days, and found that such a chronic, monocular activation induced a shift in ocular dominance of visual responses of cortical neurons.