Hofer Katharina T, Kandrács Ágnes, Ulbert István, Pál Ildikó, Szabó Csilla, Héja László, Wittner Lucia
Department of Comparative Psychophysiology, Institute of Cognitive Neuroscience and Psychology, Research Center for Natural Sciences, Hungarian Academy of Sciences, Budapest, Hungary; Department of Information Technology and Bionics, Péter Pázmány Catholic University, Budapest, Hungary.
Hippocampus. 2015 Feb;25(2):169-86. doi: 10.1002/hipo.22361. Epub 2014 Sep 25.
Hippocampal sharp wave-ripples (SPW-Rs) occur during slow wave sleep and behavioral immobility and are thought to play an important role in memory formation. We investigated the cellular and network properties of SPW-Rs with simultaneous laminar multielectrode and intracellular recordings in a rat hippocampal slice model, using physiological bathing medium. Spontaneous SPW-Rs were generated in the dentate gyrus (DG), CA3, and CA1 regions. These events were characterized by a local field potential gradient (LFPg) transient, increased fast oscillatory activity and increased multiple unit activity (MUA). Two types of SPW-Rs were distinguished in the CA3 region based on their different LFPg and current source density (CSD) pattern. Type 1 (T1) displayed negative LFPg transient in the pyramidal cell layer, and the associated CSD sink was confined to the proximal dendrites. Type 2 (T2) SPW-Rs were characterized by positive LFPg transient in the cell layer, and showed CSD sinks involving both the apical and basal dendrites. In both types, consistent with the somatic CSD source, only a small subset of CA3 pyramidal cells fired, most pyramidal cells were hyperpolarized, while most interneurons increased firing rate before the LFPg peak. Different neuronal populations, with different proportions of pyramidal cells and distinct subsets of interneurons were activated during T1 and T2 SPW-Rs. Activation of specific inhibitory cell subsets-with the possible leading role of perisomatic interneurons-seems to be crucial to synchronize distinct ensembles of CA3 pyramidal cells finally resulting in the expression of different SPW-R activities. This suggests that the hippocampus can generate dynamic changes in its activity stemming from the same excitatory and inhibitory circuits, and so, might provide the cellular and network basis for an input-specific and activity-dependent information transmission.
海马体尖波涟漪（SPW-Rs）出现在慢波睡眠和行为静止期间，被认为在记忆形成中起重要作用。我们在大鼠海马体切片模型中，使用生理浴液，通过同时进行层流多电极和细胞内记录，研究了SPW-Rs的细胞和网络特性。自发的SPW-Rs在齿状回（DG）、CA3和CA1区域产生。这些事件的特征是局部场电位梯度（LFPg）瞬变、快速振荡活动增加和多单位活动（MUA）增加。根据不同的LFPg和电流源密度（CSD）模式，在CA3区域区分出两种类型的SPW-Rs。1型（T1）在锥体细胞层显示负LFPg瞬变，相关的CSD汇局限于近端树突。2型（T2）SPW-Rs的特征是细胞层出现正LFPg瞬变，并显示CSD汇涉及顶端和基部树突。在这两种类型中，与体细胞CSD源一致，只有一小部分CA3锥体细胞放电，大多数锥体细胞超极化，而大多数中间神经元在LFPg峰值之前放电率增加。在T1和T2 SPW-Rs期间，不同比例的锥体细胞和不同子集的中间神经元组成的不同神经元群体被激活。特定抑制性细胞子集的激活——可能以胞周中间神经元起主要作用——似乎对于同步CA3锥体细胞的不同集群至关重要，最终导致不同SPW-R活动的表达。这表明海马体可以从相同的兴奋性和抑制性回路产生其活动的动态变化，因此，可能为输入特异性和活动依赖性信息传递提供细胞和网络基础。
