Wilson D A
Department of Zoology, University of Oklahoma, Norman, Oklahoma 73019, USA.
J Neurophysiol. 2000 Dec;84(6):3036-42. doi: 10.1152/jn.2000.84.6.3036.
Recent work in the anterior piriform cortex (aPCX) has demonstrated that cortical odor receptive fields are highly dynamic, showing rapid changes of both firing rate and temporal patterning within relatively few inhalations of an odor, despite relatively maintained, patterned input from olfactory bulb mitral/tufted cells. The present experiment examined the precision (odor-specificity) of this receptive field plasticity and compared it with the primary cortical afferent, olfactory bulb mitral/tufted cells. Adult Long-Evans hooded rats, urethan anesthetized and freely breathing, were used for single-unit recording from mitral/tufted and aPCX layer II/III neurons. Partial mapping of receptive fields to alkane odors (pentane, heptane, and nonane) was performed before and immediately after habituation (50-s exposure) to one of the alkanes. The results demonstrated that odor habituation of aPCX responses was odor specific, with minimal cross-habituation between alkanes differing by as few as two carbons. Mitral/tufted cells, however, showed strong cross-habituation within the odor set with the most profound cross effects to carbon chains shorter than the habituating stimulus. The results suggest that although mitral/tufted cells and aPCX neurons have roughly similar odor receptive fields, aPCX neurons have significantly better odor discrimination within their receptive field. The results have important implications for understanding the underlying bases of receptive fields in olfactory system neurons and the mechanisms of odor discrimination and memory.
最近在前梨状皮层（aPCX）开展的研究表明，皮层气味感受野具有高度动态性，尽管来自嗅球二尖瓣/簇状细胞的输入相对保持稳定且有模式，但在相对较少的几次气味吸入过程中，其放电率和时间模式都会迅速变化。本实验研究了这种感受野可塑性的精确性（气味特异性），并将其与初级皮层传入神经——嗅球二尖瓣/簇状细胞进行了比较。实验采用成年Long-Evans有帽大鼠，用乌拉坦麻醉并使其自由呼吸，对二尖瓣/簇状细胞和aPCX第II/III层神经元进行单单元记录。在对其中一种烷烃进行习惯化处理（50秒暴露）之前和之后，立即对烷烃气味（戊烷、庚烷和壬烷）的感受野进行部分映射。结果表明，aPCX反应的气味习惯化具有气味特异性，在相差仅两个碳原子的烷烃之间，交叉习惯化程度最低。然而，二尖瓣/簇状细胞在气味组内表现出强烈的交叉习惯化，对短于习惯化刺激碳链的碳链产生的交叉效应最为显著。结果表明，尽管二尖瓣/簇状细胞和aPCX神经元的气味感受野大致相似，但aPCX神经元在其感受野内具有明显更好的气味辨别能力。这些结果对于理解嗅觉系统神经元感受野的潜在基础以及气味辨别和记忆机制具有重要意义。
