Centre National de la Recherche Scientifique Unité Mixte de Recherche 8195, Centre de Neurosciences Paris-Sud, Orsay, France.
J Neurophysiol. 2010 May;103(5):2633-41. doi: 10.1152/jn.01075.2009. Epub 2010 Feb 17.
The hippocampus and olfactory regions are anatomically close, and both play a major role in memory formation. However, the way they interact during odor processing is still unclear. In both areas, strong oscillations of the local field potential (LFP) can be recorded, and are modulated by behavior. In particular, in the olfactory system, the beta rhythm (15-35 Hz) is associated with cognitive processing of an olfactory stimulus. Using LFP recordings in the olfactory bulb and dorsal and ventral hippocampus during performance of an olfactory go/no-go task in rats, we previously showed that beta oscillations are also present in the hippocampus, coherent with those in the olfactory bulb, during odor sampling. In this study, we provide further insight into information transfer in the olfacto-hippocampal network by using directional coherence (DCOH estimate), a method based on the temporal relation between two or more signals in the frequency domain. In the theta band (6-12 Hz), coherence between the olfactory bulb (OB) and the hippocampus (HPC) is weak and can be both in the feedback and feedforward directions. However, at this frequency, modulation of the coupling between the dorsal and ventral hippocampus is seen during stimulus expectation versus odor processing. In the beta frequency band (15-35 Hz), analysis showed a strong unidirectional coupling from the OB to dorsal and ventral HPC, indicating that, during odor processing, beta oscillations in the hippocampus are driven by the olfactory bulb.
海马体和嗅觉区域在解剖学上是接近的，并且都在记忆形成中发挥主要作用。然而，它们在嗅觉处理过程中相互作用的方式仍不清楚。在这两个区域中，都可以记录到局部场电位（LFP）的强振荡，并受行为调节。特别是在嗅觉系统中，β节律（15-35 Hz）与嗅觉刺激的认知处理有关。在大鼠进行嗅觉 Go/No-Go 任务期间，使用嗅球和背侧和腹侧海马体的 LFP 记录，我们之前显示β振荡也存在于海马体中，与嗅球中的振荡相干，在气味采样期间。在这项研究中，我们通过使用方向相干性（DCOH 估计）提供了对嗅觉 - 海马网络中信息传递的进一步了解，这是一种基于两个或多个信号在频域中的时间关系的方法。在 theta 频段（6-12 Hz）中，嗅球（OB）和海马体（HPC）之间的相干性较弱，并且可以在反馈和前馈方向上。然而，在这个频率下，在刺激预期与气味处理期间，观察到背侧和腹侧海马体之间的耦合调制。在β频带（15-35 Hz）中，分析显示从 OB 到背侧和腹侧 HPC 的强单向耦合，表明在嗅觉处理过程中，海马体中的β振荡是由嗅球驱动的。
