Shepherd Gordon M
Department of Neurobiology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06510, USA.
Ann N Y Acad Sci. 2007 Dec;1121:87-101. doi: 10.1196/annals.1401.032. Epub 2007 Sep 13.
The orbitofrontal cortex receives inputs from all the major sensory pathways, but olfaction is the only pathway that projects directly to it. We discuss several unique properties with which this is associated. Olfactory stimuli are converted into spatial images, varying in time, in the olfactory bulb, which are processed by the olfactory cortex for input to orbitofrontal cortex. The input from olfactory cortex to orbitofrontal cortex is mostly direct, though some fibers project through mediodorsal thalamus in some species. Studies are needed to determine the specific contributions of olfactory cortex and orbitofrontal cortex to conscious smell perception. A major challenge to the field is accounting for how conscious perception of this sense is coordinated with conscious perceptions of the other major senses, which are known to depend on thalamocortical circuits. The fact that the primary olfactory area at the neocortical level is embedded in the multisensory region of the orbitofrontal cortex indicates that at this level smell perception is heavily influenced by other senses, particularly related to food flavors through retronasal smell, which is being documented in experimental studies in rodents, nonhuman primates, and humans. Also requiring clarification is how behavioral modulation at each step of processing of the odor images is coordinated. In sum, the orbitofrontal cortex is emerging as the next frontier in understanding the neural basis of smell.
眶额皮质接收来自所有主要感觉通路的输入，但嗅觉是唯一直接投射到该区域的通路。我们讨论了与之相关的几个独特特性。嗅觉刺激在嗅球中被转换为随时间变化的空间图像，这些图像由嗅觉皮质处理后输入到眶额皮质。从嗅觉皮质到眶额皮质的输入大多是直接的，不过在某些物种中，一些纤维会通过丘脑背内侧核投射。需要开展研究来确定嗅觉皮质和眶额皮质对有意识嗅觉感知的具体贡献。该领域面临的一个主要挑战是解释这种感觉的有意识感知是如何与其他主要感觉的有意识感知相协调的，已知其他主要感觉依赖于丘脑皮质回路。新皮质水平的主要嗅觉区域嵌入眶额皮质的多感觉区域，这一事实表明在这个水平上，嗅觉感知受到其他感觉的严重影响，特别是通过鼻后嗅觉与食物味道相关，这一点已在啮齿动物、非人灵长类动物和人类的实验研究中得到证实。同样需要阐明的是，气味图像处理的每个步骤中的行为调节是如何协调的。总之，眶额皮质正在成为理解嗅觉神经基础的下一个前沿领域。
