Department of Neurobiology, Yale University School of Medicine, New Haven, CT, USA.
Eur J Neurosci. 2012 Feb;35(3):389-401. doi: 10.1111/j.1460-9568.2011.07978.x. Epub 2012 Jan 25.
The synchronization of neuronal activity is thought to enhance information processing. There is much evidence supporting rhythmically bursting external tufted cells (ETCs) of the rodent olfactory bulb glomeruli coordinating the activation of glomerular interneurons and mitral cells via dendrodendritic excitation. However, as bursting has variable significance at axodendritic cortical synapses, it is not clear if ETC bursting imparts a specific functional advantage over the preliminary spike in dendrodendritic synaptic networks. To answer this question, we investigated the influence of single ETC bursts and spikes with the in vitro rat olfactory bulb preparation at different levels of processing, via calcium imaging of presynaptic ETC dendrites, dual electrical recording of ETC -interneuron synaptic pairs, and multicellular calcium imaging of ETC-induced population activity. Our findings supported single ETC bursts, versus single spikes, driving robust presynaptic calcium signaling, which in turn was associated with profound extension of the initial monosynaptic spike-driven dendrodendritic excitatory postsynaptic potential. This extension could be driven by either the spike-dependent or spike-independent components of the burst. At the population level, burst-induced excitation was more widespread and reliable compared with single spikes. This further supports the ETC network, in part due to a functional advantage of bursting at excitatory dendrodendritic synapses, coordinating synchronous activity at behaviorally relevant frequencies related to odor processing in vivo.
神经元活动的同步被认为可以增强信息处理。有大量证据表明，啮齿动物嗅球小球外部丛状细胞（ETC）的节律性爆发通过树突-树突兴奋协调小球间神经元和僧帽细胞的激活。然而，由于爆发在轴突-树突皮质突触处具有不同的意义，因此尚不清楚 ETC 爆发是否比树突-树突突触网络中的初步尖峰赋予特定的功能优势。为了回答这个问题，我们通过在不同处理水平的体外大鼠嗅球标本中进行钙成像、ETC-中间神经元突触对的双电记录以及 ETC 诱导的群体活动的多细胞钙成像，研究了单个 ETC 爆发和尖峰的影响。我们的发现支持单个 ETC 爆发而非单个尖峰驱动强大的突触前钙信号，这反过来又与初始单突触尖峰驱动的树突-树突兴奋性突触后电位的深度扩展有关。这种扩展可以由爆发的尖峰依赖性或尖峰非依赖性成分驱动。在群体水平上，与单个尖峰相比，爆发诱导的兴奋更广泛且更可靠。这进一步支持了 ETC 网络，部分原因是爆发在兴奋性树突-树突突触处具有功能优势，协调与体内气味处理相关的行为相关频率的同步活动。
