Bruno Randy M, Sakmann Bert
Department of Cell Physiology, Max Planck Institute for Medical Research, Jahnstrasse 29, 69120 Heidelberg, Germany.
Science. 2006 Jun 16;312(5780):1622-7. doi: 10.1126/science.1124593.
Sensory stimuli reach the brain via the thalamocortical projection, a group of axons thought to be among the most powerful in the neocortex. Surprisingly, these axons account for only approximately 15% of synapses onto cortical neurons. The thalamocortical pathway might thus achieve its effectiveness via high-efficacy thalamocortical synapses or via amplification within cortical layer 4. In rat somatosensory cortex, we measured in vivo the excitatory postsynaptic potential evoked by a single synaptic connection and found that thalamocortical synapses have low efficacy. Convergent inputs, however, are both numerous and synchronous, and intracortical amplification is not required. Our results suggest a mechanism of cortical activation by which thalamic input alone can drive cortex.
感觉刺激通过丘脑皮质投射到达大脑，这是一组轴突，被认为是新皮质中最强大的轴突之一。令人惊讶的是，这些轴突仅占皮质神经元突触的约15%。丘脑皮质通路可能因此通过高效能的丘脑皮质突触或通过皮质第4层内的放大作用来实现其有效性。在大鼠体感皮质中，我们在体内测量了单个突触连接诱发的兴奋性突触后电位，发现丘脑皮质突触效能较低。然而，汇聚输入既多又同步，不需要皮质内放大。我们的结果提示了一种皮质激活机制，通过该机制，仅丘脑输入就能驱动皮质。
