Programa de Fisiología y Biofísica and Centro de Neurociencias Integradas, Facultad de Medicina, Universidad de Chile, Casilla 70005, Santiago, Chile.
Eur J Neurosci. 2011 Sep;34(5):787-99. doi: 10.1111/j.1460-9568.2011.07800.x. Epub 2011 Aug 8.
Mammals actively sample the environment for relevant olfactory objects. This active sampling is revealed by rapid changes in respiratory rate that influence the olfactory input. Yet the role of sniffing in shaping the neural responses to odorants has not been elucidated. In the olfactory bulb (OB), odorant-evoked gamma oscillations reflect the synchronous activity of mitral/tufted cells, a proposed mechanism for odorant representation. Here we examined the effect of sniffing frequency on the odorant-evoked gamma oscillations in the OB. We simultaneously recorded the respiratory rate and the local field potential while rats performed a lick/no-lick olfactory discrimination task with low odorant concentrations. High-frequency sniffing (HFS) augmented the power of gamma oscillations, suggesting an increase in the sensitivity to odorants. By contrast, coupling of the gamma oscillations to the sniff cycle and the amplitude of individual bursts were not modified by the respiratory rate. However, HFS prolonged the overall response to odorants and increased the frequency of the gamma oscillations, indicating that HFS reduces the adaptation to continuous odorant stimulation. Therefore, the increase in gamma power during HFS is the result of more frequent gamma bursts and the extended response to odorants. As odorant discrimination can be performed in a single sniff, a reduction in the adaptation mediated by HFS of novel odorants may facilitate odorant memory formation for subsequent odorant identification. Finally, these results corroborate that olfactory sampling should be integrated to the study of odorant coding in behaving animals.
哺乳动物积极地从环境中采样相关的嗅觉对象。这种主动采样是通过影响嗅觉输入的呼吸率的快速变化来揭示的。然而,嗅探在塑造对气味的神经反应中的作用尚未阐明。在嗅球 (OB) 中,气味诱发的伽马振荡反映了嗅球内神经元同步活动,这是气味表示的一种机制。在这里,我们研究了嗅探频率对 OB 中气味诱发的伽马振荡的影响。当大鼠在低浓度气味环境下进行舔/不舔嗅觉辨别任务时,我们同时记录了呼吸率和局部场电位。高频嗅探 (HFS) 增强了伽马振荡的功率,表明对气味的敏感性增加。相比之下,伽马振荡与嗅探周期的耦合和单个爆发的幅度不受呼吸率的影响。然而,HFS 延长了对气味的整体反应并增加了伽马振荡的频率,表明 HFS 减少了对连续气味刺激的适应。因此,HFS 期间伽马功率的增加是由于伽马爆发更频繁和对气味的反应时间延长所致。由于气味辨别可以在单次嗅探中完成,因此 HFS 减少了对新气味的适应,可能有助于随后的气味识别中气味记忆的形成。最后,这些结果证实了嗅觉采样应该与行为动物的气味编码研究相结合。