Litaudon P, Garcia S, Buonviso N
Neurosciences Sensorielles, Comportement, Cognition, CNRS UMR 5020-Université Lyon 1, Université de Lyon, Institut Fédératif des Neurosciences de Lyon, 50 avenue Tony Garnier, 69366 Lyon cedex 07, France.
Neuroscience. 2008 Oct 15;156(3):781-7. doi: 10.1016/j.neuroscience.2008.07.077. Epub 2008 Aug 22.
Oscillatory activity is a prominent characteristic of electrophysiological recordings in the olfactory system and has been proposed to play a key role in encoding olfactory representations. Studies in several systems have shown that some aspects of information coding involve characteristics that intertwine spikes and fast oscillations (in the beta and gamma range) of local field potentials (LFP). In the insect olfactory system, it has been proposed that oscillatory activity could provide a temporal link between cells. Following previous data, we have proposed that gamma band oscillations in mammals could subserve a gating function for the transfer of information between the olfactory bulb (OB) and the anterior piriform cortex (aPC), which are functionally coupled. In this study, we used an electrophysiological approach to investigate the temporal relationship between LFP gamma oscillations and single-unit activity by simultaneously recording LFP and single unit discharges in the rat aPC during odor evoked activity. Our data showed that mean spike discharges and gamma oscillatory bursts were synchronized with the same respiratory cycle epoch (around the inspiration/expiration transition). Temporal correlations between spikes and LFP revealed that cortical cell spikes were tightly phase-coupled with the peak of gamma oscillations and that this phase-coupling was not odor-dependent. Our results suggest that gamma oscillation may act as a temporal filter. Oscillatory phase-coupled spikes in the OB could act in increasing the probability of spike emission in the aPC cell during a narrow time-window, explaining the tight phase-coupling observed in the aPC. The role of spike-LFP phase-coupling as a binding function between odor features is discussed.
振荡活动是嗅觉系统电生理记录的一个显著特征，并且有人提出它在编码嗅觉表征中起关键作用。在多个系统中的研究表明，信息编码的某些方面涉及到将动作电位与局部场电位（LFP）的快速振荡（β和γ频段）交织在一起的特征。在昆虫嗅觉系统中，有人提出振荡活动可以在细胞之间提供时间联系。根据先前的数据，我们提出哺乳动物中的γ频段振荡可能为嗅球（OB）和前梨状皮质（aPC）之间的信息传递起到门控作用，这两者在功能上是耦合的。在本研究中，我们采用电生理方法，通过在大鼠aPC中气味诱发活动期间同时记录LFP和单个神经元放电，来研究LFP γ振荡与单个神经元活动之间的时间关系。我们的数据表明，平均动作电位发放和γ振荡爆发与相同的呼吸周期阶段（在吸气/呼气转换附近）同步。动作电位与LFP之间的时间相关性表明，皮质细胞动作电位与γ振荡的峰值紧密相位耦合，并且这种相位耦合不依赖于气味。我们的结果表明，γ振荡可能起到时间滤波器的作用。OB中振荡相位耦合的动作电位可能在一个狭窄的时间窗口内增加aPC细胞中动作电位发放的概率，这解释了在aPC中观察到的紧密相位耦合。我们还讨论了动作电位-LFP相位耦合作为气味特征之间的绑定功能的作用。
