Department of Anatomy and Neurobiology, University of Tennessee Health Science Center, Memphis, TN 38163, USA.
Exp Biol Med (Maywood). 2020 Mar;245(5):448-455. doi: 10.1177/1535370220909096. Epub 2020 Feb 27.
While the cortical representation of sensory stimuli is well described for some sensory systems, a clear understanding of the cortical representation of taste stimuli remains elusive. Recent investigations have focused on both spatial and temporal organization of taste responses in the putative taste region of insular cortex. This review highlights recent literature focused on spatiotemporal coding strategies in insular cortex. These studies are examined in the context of the organization and function of the entire insular cortex, rather than a specific gustatory region of insular cortex. In regard to a taste quality-specific map, imaging studies have reported conflicting results, whereas electrophysiology studies have described a broad distribution of taste-responsive neurons found throughout insular cortex with no spatial organization. The current collection of evidence suggests that insular cortex may be organized into a hedonic or “viscerotopic” map, rather than one ordered according to taste quality. Further, it has been proposed that cortical taste responses can be separated into temporal “epochs” representing stimulus identity and palatability. This coding strategy presents a potential framework, whereby the coordinated activity of a population of neurons allows for the same neurons to respond to multiple taste stimuli or even other sensory modalities, a well-documented phenomenon in insular cortex neurons. However, these representations may not be static, as several studies have demonstrated that both spatial representation and temporal dynamics of taste coding change with experience. Collectively, these studies suggest that cortical taste representation is not organized in a spatially discrete map, but rather is plastic and spatially dispersed, using temporal information to encode multiple types of information about ingested stimuli.
The organization of taste coding in insular cortex is widely debated. While early work has focused on whether taste quality is encoded via labeled line or ensemble mechanisms, recent work has attempted to delineate the spatial organization and temporal components of taste processing in insular cortex. Recent imaging and electrophysiology studies have reported conflicting results in regard to the spatial organization of cortical taste responses, and many studies ignore potentially important temporal dynamics when investigating taste processing. This review highlights the latest research in these areas and examines them in the context of the anatomy and physiology of the insular cortex in general to provide a more comprehensive description of taste coding in insular cortex.
虽然某些感觉系统的感觉刺激皮质代表已得到很好的描述，但味觉刺激的皮质代表仍难以捉摸。最近的研究集中在岛叶皮质假定味觉区域的味觉反应的空间和时间组织上。这篇综述强调了最近关于岛叶皮质时空编码策略的文献。这些研究是在整个岛叶皮质的组织和功能背景下进行的，而不是岛叶皮质的特定味觉区域。关于味觉质量特异性图谱，成像研究报告了相互矛盾的结果，而电生理学研究则描述了整个岛叶皮质中发现的广泛分布的味觉反应神经元，没有空间组织。目前的证据表明，岛叶皮质可能组织成一个愉快的或“内脏图谱”，而不是根据味觉质量有序排列。此外，有人提出，皮质味觉反应可以分为代表刺激身份和可接受性的时间“时段”。这种编码策略提供了一个潜在的框架，即一群神经元的协调活动允许相同的神经元对多种味觉刺激甚至其他感觉模式做出反应，这是岛叶皮质神经元中一个有充分记录的现象。然而，这些表示形式可能不是静态的，因为几项研究表明，味觉编码的空间表示和时间动态都随着经验而变化。总的来说，这些研究表明，皮质味觉表示不是按照空间离散图谱组织的，而是具有可塑性和空间分散性，使用时间信息对摄入刺激的多种类型信息进行编码。
岛叶皮质的味觉编码组织存在广泛争议。虽然早期的工作集中在味觉质量是否通过标记线或集合机制进行编码，但最近的工作试图描绘岛叶皮质中味觉处理的空间组织和时间成分。最近的成像和电生理学研究在皮质味觉反应的空间组织方面报告了相互矛盾的结果，并且许多研究在研究味觉处理时忽略了潜在的重要时间动态。这篇综述强调了这些领域的最新研究，并在岛叶皮质的解剖学和生理学背景下对其进行了检查，以更全面地描述岛叶皮质中的味觉编码。
