Nguyen Chi Vivan, Müller Carola, Wolfenstetter Thérèse, Yanovsky Yevgenij, Draguhn Andreas, Tort Adriano B L, Brankačk Jurij
Institute for Physiology and Pathophysiology, University Heidelberg, 69120 Heidelberg, Germany, and.
Brain Institute, Federal University of Rio Grande do Norte, 59056-450 Natal, Rio Grande do Norte, Brazil.
J Neurosci. 2016 Jan 6;36(1):162-77. doi: 10.1523/JNEUROSCI.2848-15.2016.
We have recently described a slow oscillation in the hippocampus of urethane-anesthetized mice, which couples to nasal respiration and is clearly distinct from co-occurring theta oscillations. Here we set out to investigate whether such type of patterned network activity, which we named "hippocampal respiration rhythm" (HRR), also occurs in awake mice. In freely moving mice, instantaneous respiration rate is extremely variable, and respiration is superimposed by bouts of sniffing. To reduce this variability, we clamped the behavior of the animal to either awake immobility or treadmill running by using a head-fixed setup while simultaneously recording respiration and field potentials from the olfactory bulb (OB) and hippocampus. Head-fixed animals often exhibited long periods of steady respiration rate during either immobility or running, which allowed for spectral and coherence analyses with a sufficient frequency resolution to sort apart respiration and theta activities. We could thus demonstrate the existence of HRR in awake animals, namely, a respiration-entrained slow rhythm with highest amplitude at the dentate gyrus. HRR was most prominent during immobility and running with respiration rates slower than theta oscillations. Nevertheless, HRR could also be faster than theta. Discharges of juxtacellularly recorded cells in CA1 and dentate gyrus were modulated by HRR and theta oscillations. Granger directionality analysis revealed that HRR is caused by the OB and that theta oscillations in OB are caused by the hippocampus. Our results suggest that respiration-coupled oscillations aid the exchange of information between olfactory and memory networks.
Olfaction is a major sense in rodents. In consequence, the olfactory bulb (OB) should be able to transmit information to downstream regions. Here we report potential mechanisms underlying such information transfer. We demonstrate the existence of a respiration-entrained rhythm in the hippocampus of awake mice. Frequencies of the hippocampal respiration rhythm (HRR) overlap with classical theta oscillations, but both rhythms are clearly distinct. HRR is most prominent in the dentate gyrus, especially when respiration is slower than theta frequency. Discharges of neurons in CA1 and dentate gyrus are modulated by both HRR and theta. Directionality analysis shows that HRR is caused by the OB. Our results suggest that respiration-coupled oscillations aid the exchange of information between olfactory and memory networks.
我们最近描述了在氨基甲酸乙酯麻醉的小鼠海马体中存在一种缓慢振荡，它与鼻腔呼吸耦合，且明显不同于同时出现的theta振荡。在此，我们着手研究这种我们命名为“海马体呼吸节律”（HRR）的模式化网络活动是否也出现在清醒小鼠中。在自由活动的小鼠中，瞬时呼吸频率变化极大，且呼吸会叠加有阵阵嗅吸动作。为了减少这种变异性，我们通过使用头部固定装置将动物行为限制为清醒不动或在跑步机上奔跑，同时记录嗅球（OB）和海马体的呼吸及场电位。头部固定的动物在不动或奔跑时常常会出现长时间稳定的呼吸频率，这使得能够进行具有足够频率分辨率的频谱和相干分析，以区分呼吸和theta活动。因此，我们能够证明清醒动物中存在HRR，即在齿状回具有最高振幅的一种呼吸驱动的缓慢节律。HRR在不动和奔跑且呼吸频率慢于theta振荡时最为显著。然而，HRR也可能比theta更快。CA1和齿状回中细胞外记录的细胞放电受HRR和theta振荡的调制。格兰杰方向性分析表明，HRR由OB引起，而OB中的theta振荡由海马体引起。我们的结果表明，呼吸耦合振荡有助于嗅觉和记忆网络之间的信息交换。
嗅觉是啮齿动物的主要感官。因此，嗅球（OB）应该能够将信息传递到下游区域。在此我们报告了这种信息传递背后的潜在机制。我们证明了清醒小鼠海马体中存在一种呼吸驱动的节律。海马体呼吸节律（HRR）的频率与经典theta振荡重叠，但这两种节律明显不同。HRR在齿状回中最为显著，尤其是当呼吸慢于theta频率时。CA1和齿状回中神经元的放电受HRR和theta两者的调制。方向性分析表明，HRR由OB引起。我们的结果表明，呼吸耦合振荡有助于嗅觉和记忆网络之间的信息交换。
