Martin Claire, Gervais Rémi, Hugues Etienne, Messaoudi Belkacem, Ravel Nadine
Institut des Sciences Cognitives, Centre National de la Recherche Scientifique-Université Lyon I Unité Mixte de Recherche 5015, Bron, 69675 France.
J Neurosci. 2004 Jan 14;24(2):389-97. doi: 10.1523/JNEUROSCI.3433-03.2004.
In the first relay of information processing, the olfactory bulb (OB), odors are known to generate specific spatial patterns of activity. Recently, in freely behaving rats, we demonstrated that learning modulated oscillatory activity in local field potential (LFP), in response to odors, in both beta (15-40 Hz) and gamma (60-90 Hz) bands. The present study further characterized this odor-induced oscillatory activity with emphasis on its spatiotemporal distribution over the olfactory bulb and on its relationship with improvement of behavioral performances along training. For that purpose, LFPs were simultaneously recorded from four locations in the OB in freely moving rats performing an olfactory discrimination task. Electrodes were chronically implanted near relay neurons in the mitral cell body layer. Time-frequency methods were used to extract signal characteristics (amplitude, frequency, and time course) in the two frequency bands. Before training, odor presentation produced, on each site, a power decrease in gamma oscillations and a weak but significant increase in power of beta oscillations (approximately 25 Hz). When the training was achieved, these two phenomena were amplified. Interestingly, the beta oscillatory response showed several significant differences between the anterodorsal and posteroventral regions of the OB. In addition, clear-cut beta responses occurred in the signal as soon as animals began to master the task. As a whole, our results point to the possible functional importance of beta oscillatory activity in the mammalian OB, particularly in the context of olfactory learning.
在信息处理的首个中继站——嗅球（OB）中，已知气味会产生特定的空间活动模式。最近，在自由活动的大鼠中，我们证明学习会调节局部场电位（LFP）中的振荡活动，以响应气味，这种调节在β（15 - 40赫兹）和γ（60 - 90赫兹）频段均有体现。本研究进一步对这种气味诱发的振荡活动进行了特征描述，重点关注其在嗅球上的时空分布以及与训练过程中行为表现改善的关系。为此，在自由活动的大鼠执行嗅觉辨别任务时，从嗅球的四个位置同时记录局部场电位。电极被长期植入到二尖瓣细胞体层的中继神经元附近。采用时频方法提取两个频段的信号特征（幅度、频率和时间进程）。在训练前，气味呈现会使每个部位的γ振荡功率降低，β振荡功率有微弱但显著的增加（约25赫兹）。当训练完成时，这两种现象会被放大。有趣的是，β振荡反应在嗅球的前背侧和后腹侧区域之间表现出几个显著差异。此外，一旦动物开始掌握任务，信号中就会出现明确的β反应。总体而言，我们的结果表明β振荡活动在哺乳动物嗅球中可能具有重要的功能意义，特别是在嗅觉学习的背景下。
