嗅球僧帽细胞具有编码气味空间信息的能力

刺激源的方位是刺激的重要特性之一.行为学的研究发现,动物能够利用气味到达左右鼻腔的时间差和强度差信息对气味方位进行感知,但作为嗅觉系统第一神经中枢的嗅球,是否具有利用两侧鼻间差信息对气味方位进行编码的能力一直受到质疑.为探讨该问题,在本研究中通过比较嗅球中84个僧帽细胞对同侧气味刺激、对侧气味刺激以及对侧气味刺激略先于同侧气味刺激时的反应,发现有29个僧帽细胞可被同侧气味所兴奋,其中18个虽然对对侧气味刺激不反应,但对侧气味的存在却能显著降低其对同侧气味刺激的反应.另外,50个僧帽细胞在只给予同侧或对侧气味刺激时不反应,但其中11个在对侧刺激略先于同侧刺激的方式给出气味时,表现出明显的兴奋性反应.我们的研究结果一方面提示僧帽细胞具有编码气味到达两个鼻腔的时间差,或气味源位置信息的能力;另一方面也表明对侧刺激不仅能对同侧嗅球僧帽细胞产生抑制效应,还可能存在目前还不明确的机制而产生兴奋效应.

Mitral Cells of Olfactory Bulb Are Capable of Encoding Odor Location

One of the most important properties of a stimulus is its location. The behavioral studies indicate that animals can perceive odor locations by comparing the time/concentration differences produced at the two nostrils. However, it is still controversial that the olfactory bulb, which is the first center in olfactory pathway, has the ability to encode the odor location information. To clarify the debate, we compared the responses of 84 mitral cells to three different odor stimulation modes in present study: odor to ipsilateral nose only, to contralateral nose only, and to both noses with the contralateral stimulation preceding the ipsilateral. We found that 29 cells showed excitatory responses to ipsilateral odor stimulation, and 18 of them showed no response to contralateral stimulation. However, the presence of the contralateral odor stimulation could significantly suppress the responses elicited by ipsilateral odor stimulation. In addition, 50 of the 84 cells showed no response when the ipsilateral or contralateral odor stimulation presented alone, but 11 of them showed excitatory responses when the odor stimulation presented to both noses with contralateral stimulation preceding the ipsilateral. The results indicate that the mitral cells of the olfactory bulb have the ability to encode the time difference of the odor arriving at the two nostrils, and that the contralateral odor stimulation can enhance the response through unknown neuronal pathways.