Experience-dependent modification of synaptic plasticity in visual cortex
Experience-dependent modification of synaptic plasticity in visual cortex
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DOI：
10.1038/381526a0
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发表时间：
1996-06-06
期刊：
影响因子：
64.8
通讯作者：
Bear, MF
中科院分区：
文献类型：
--
作者：
Kirkwood, A;Rioult, MG;Bear, MF
在大脑皮层的许多区域，通过NMDA（N-甲基-D-天冬氨酸）敏感性谷氨酸受体（NMDA受体）的Ca 2+内流可触发两种形式的突触可塑性：长时程抑制（LTD）和长时程增强（LTP）（1）。LTD由低水平的突触后NMDA受体激活诱导，例如响应于低频刺激，而LTP由高频刺激后发生的较强激活诱导（2-4）。理论研究表明，突触LTD和LTP的特性可以解释发育中的视觉皮层中经验依赖性可塑性的许多方面，只要LTD-LTP交叉点（修改阈值，theta（m））作为皮层活动历史的函数而变化（5-7）。在这里，我们提供了直接的实验证据，证明θ（m）的值取决于感官经验。我们发现，在光剥夺大鼠的视觉皮层中，LTP在一系列刺激频率下增强，LTD减少，并且这些影响可以通过短短两天的光照来逆转。我们的研究结果支持这样的想法，即可变的突触修改阈值允许神经网络中的突触权重达到稳定的平衡。
IN many regions of the cerebral cortex, Ca2+ influx through NMDA (N-methyl-D-aspartate) sensitive glutamate receptors (NMDA receptors) can trigger two forms of synaptic plasticity: long-term depression (LTD) and long-term potentiation (LTP)(1). LTD is induced by low levels of postsynaptic NMDA-receptor activation, for instance in response to low-frequency stimulation, whereas LTP is induced by the stronger activation that occurs following high-frequency stimulation(2-4). Theoretical studies have shown that the properties of synaptic LTD and LTP can account for many aspects of experience-dependent plasticity in the developing visual cortex, provided that the LTD-LTP crossover point (the modification threshold, theta(m)) varies as a function of the history of cortical activity(5-7). Here we provide direct experimental evidence that the value of theta(m) depends on sensory experience. We find in visual cortex of light-deprived rats that LTP is enhanced and LTD diminished over a range of stimulation frequencies, and that these effects can be reversed by as little as two days of light exposure. Our findings support the idea that a variable synaptic-modification threshold allows synaptic weights in neural networks to achieve a stable equilibrium.