Li Anan, Guthman Ethan M, Doucette Wilder T, Restrepo Diego
Department of Cell and Developmental Biology.
Jiangsu Key Laboratory of Brain Disease and Bioinformation, Research Center for Biochemistry and Molecular Biology, Xuzhou Medical University, Xuzhou, 221004, China, and.
J Neurosci. 2017 Feb 15;37(7):1835-1852. doi: 10.1523/JNEUROSCI.3132-16.2017. Epub 2017 Jan 16.
The firing rate of the mitral/tufted cells in the olfactory bulb is known to undergo significant trial-to-trial variability and is affected by anesthesia. Here we ask whether odorant-elicited changes in firing rate depend on the rate before application of the stimulus in the awake and anesthetized mouse. We find that prestimulus firing rate varies widely on a trial-to-trial basis and that the stimulus-induced change in firing rate decreases with increasing prestimulus firing rate. Interestingly, this prestimulus firing rate dependence was different when the behavioral task did not involve detecting the valence of the stimulus. Finally, when the animal was learning to associate the odor with reward, the prestimulus firing rate was smaller for false alarms compared with correct rejections, suggesting that intrinsic activity reflects the anticipatory status of the animal. Thus, in this sensory modality, changes in behavioral status alter the intrinsic prestimulus activity, leading to a change in the responsiveness of the second-order neurons. We speculate that this trial-to-trial variability in odorant responses reflects sampling of the massive parallel input by subsets of mitral cells. The olfactory bulb must deal with processing massive parallel input from ∼1200 distinct olfactory receptors. In contrast, the visual system receives input from a small number of photoreceptors and achieves recognition of complex stimuli by allocating processing for distinct spatial locations to different brain areas. Here we find that the change in firing rate elicited by the odorant in second-order mitral cells depends on the intrinsic activity leading to a change of magnitude in the responsiveness of these neurons relative to this prestimulus activity. Further, we find that prestimulus firing rate is influenced by behavioral status. This suggests that there is top-down modulation allowing downstream brain processing areas to perform dynamic readout of olfactory information.
已知嗅球中二尖瓣/簇状细胞的放电频率在不同试验间存在显著差异，且受麻醉影响。在此，我们探究在清醒和麻醉的小鼠中，气味诱发的放电频率变化是否取决于刺激施加前的频率。我们发现，刺激前的放电频率在不同试验间差异很大，且刺激诱发的放电频率变化随刺激前放电频率的增加而减小。有趣的是，当行为任务不涉及检测刺激效价时，这种对刺激前放电频率的依赖性有所不同。最后，当动物学习将气味与奖励联系起来时，与正确拒斥相比，虚报时的刺激前放电频率更小，这表明内在活动反映了动物的预期状态。因此，在这种感觉模式中，行为状态的变化会改变刺激前的内在活动，导致二阶神经元反应性的改变。我们推测，气味反应中这种不同试验间的变异性反映了二尖瓣细胞亚群对大量并行输入的采样。嗅球必须处理来自约1200种不同嗅觉受体的大量并行输入。相比之下，视觉系统从少量光感受器接收输入，并通过将不同空间位置的处理分配到不同脑区来实现对复杂刺激的识别。在此，我们发现气味在二阶二尖瓣细胞中诱发的放电频率变化取决于内在活动，导致这些神经元相对于这种刺激前活动的反应性大小发生变化。此外，我们发现刺激前放电频率受行为状态影响。这表明存在自上而下的调节，使下游脑处理区域能够对嗅觉信息进行动态读出。
