Hahn Thomas T G, Sakmann Bert, Mehta Mayank R
Department of Cell Physiology, Max Planck Institute for Medical Research, D-69120 Heidelberg, Germany.
Proc Natl Acad Sci U S A. 2007 Mar 20;104(12):5169-74. doi: 10.1073/pnas.0700222104. Epub 2007 Mar 12.
The connectivity of the hippocampal trisynaptic circuit, formed by the dentate gyrus, the CA3 and the CA1 region, is well characterized anatomically and functionally in vitro. The functional connectivity of this circuit in vivo remains to be understood. Toward this goal, we investigated the influence of the spontaneous, synchronized oscillations in the neocortical local field potential, reflecting up-down states (UDS) of cortical neurons, on the hippocampus. We simultaneously measured the extracellular local field potential in association cortex and the membrane potential of identified hippocampal excitatory neurons in anesthetized mice. Dentate gyrus granule cells showed clear UDS modulation that was phase locked to cortical UDS with a short delay. In contrast, CA3 pyramidal neurons showed mixed UDS modulation, such that some cells were depolarized during the cortical up state and others were hyperpolarized. CA1 pyramidal neurons, located farther downstream, showed consistent UDS modulation, such that when the cortical and dentate gyrus neurons were depolarized, the CA1 pyramidal cells were hyperpolarized. These results demonstrate the differential functional connectivity between neocortex and hippocampal subfields during UDS oscillations.
由齿状回、CA3和CA1区域构成的海马三突触回路的连接性，在体外已从解剖学和功能上得到了充分表征。该回路在体内的功能连接性仍有待了解。为了实现这一目标，我们研究了反映皮质神经元上下状态（UDS）的新皮质局部场电位中的自发同步振荡对海马体的影响。我们在麻醉小鼠中同时测量了联合皮质中的细胞外局部场电位和已识别的海马兴奋性神经元的膜电位。齿状回颗粒细胞表现出清晰的UDS调制，且与皮质UDS相位锁定，延迟较短。相比之下，CA3锥体神经元表现出混合的UDS调制，即一些细胞在皮质上状态期间去极化，而另一些细胞则超极化。位于更下游的CA1锥体神经元表现出一致的UDS调制，即当皮质和齿状回神经元去极化时，CA1锥体细胞超极化。这些结果证明了在UDS振荡期间新皮质与海马亚区之间不同的功能连接性。
