Roth Fabian C, Beyer Katinka M, Both Martin, Draguhn Andreas, Egorov Alexei V
Institute of Physiology and Pathophysiology, Department of Neurophysiology, Heidelberg University, Heidelberg, D-69120, Germany.
Hippocampus. 2016 Dec;26(12):1493-1508. doi: 10.1002/hipo.22623. Epub 2016 Aug 18.
The entorhinal cortex (EC) is a critical component of the medial temporal lobe (MTL) memory system. Local networks within the MTL express a variety of state-dependent network oscillations that are believed to organize neuronal activity during memory formation. The peculiar pattern of sharp wave-ripple complexes (SPW-R) entrains neurons by a very fast oscillation at ∼200 Hz in the hippocampal areas CA3 and CA1 and then propagates through the "output loop" into the EC. The precise mechanisms of SPW-R propagation and the resulting cellular input patterns in the mEC are, however, largely unknown. We therefore investigated the activity of layer V (LV) principal neurons of the medial EC (mEC) during SPW-R oscillations in horizontal mouse brain slices. Intracellular recordings in the mEC were combined with extracellular monitoring of propagating network activity. SPW-R in CA1 were regularly followed by negative field potential deflections in the mEC. Propagation of SPW-R activity from CA1 to the mEC was mostly monosynaptic and excitatory, such that synaptic input to mEC LV neurons directly reflected unit activity in CA1. Comparison with propagating network activity from CA3 to CA1 revealed a similar role of excitatory long-range connections for both regions. However, SPW-R-induced activity in CA1 involved strong recruitment of rhythmic synaptic inhibition and corresponding fast field oscillations, in contrast to the mEC. These differences between features of propagating SPW-R emphasize the differential processing of network activity by each local network of the hippocampal output loop. © 2016 Wiley Periodicals, Inc.
内嗅皮质(EC)是内侧颞叶(MTL)记忆系统的关键组成部分。MTL内的局部网络表现出多种与状态相关的网络振荡,据信这些振荡在记忆形成过程中组织神经元活动。尖锐波-涟漪复合体(SPW-R)的特殊模式通过海马CA3区和CA1区约200Hz的快速振荡带动神经元,然后通过“输出环路”传播到EC。然而,SPW-R传播的精确机制以及在mEC中产生的细胞输入模式在很大程度上尚不清楚。因此,我们研究了水平小鼠脑片中SPW-R振荡期间内侧EC(mEC)第V层(LV)主要神经元的活动。mEC中的细胞内记录与传播网络活动的细胞外监测相结合。CA1区的SPW-R之后通常会在mEC中出现负向场电位偏转。SPW-R活动从CA1区传播到mEC大多是单突触且兴奋性的,因此mEC LV神经元的突触输入直接反映了CA1区的单位活动。与从CA3区传播到CA1区的网络活动进行比较,发现这两个区域的兴奋性长程连接具有相似的作用。然而,与mEC不同,CA1区中SPW-R诱导的活动涉及有节奏的突触抑制的强烈募集以及相应的快速场振荡。传播的SPW-R特征之间的这些差异强调了海马输出环路每个局部网络对网络活动的差异处理。©2016威利期刊公司