Di Lorenzo Patricia M, Chen Jen-Yung, Victor Jonathan D
Department of Psychology, Binghamton University, Binghamton, New York 13902-6000, USA.
J Neurosci. 2009 Jul 22;29(29):9227-38. doi: 10.1523/JNEUROSCI.5995-08.2009.
Receptive fields of sensory neurons in the brain are usually restricted to a portion of the entire stimulus domain. At all levels of the gustatory neuraxis, however, there are many cells that are broadly tuned, i.e., they respond well to each of the basic taste qualities (sweet, sour, salty, and bitter). Although it might seem that this broad tuning precludes a major role for these cells in representing taste space, here we show the opposite--namely, that the tastant-specific temporal aspects (firing rate envelope and spike timing) of their responses enable each cell to represent the entire stimulus domain. Specifically, we recorded the response patterns of cells in the nucleus of the solitary tract (NTS) to representatives of four basic taste qualities and their binary mixtures. We analyzed the temporal aspects of these responses, and used their similarities and differences to construct the taste space represented by each neuron. We found that for the more broadly tuned neurons in the NTS, the taste space is a systematic representation of the entire taste domain. That is, the taste space of these broadly tuned neurons is three dimensional, with basic taste qualities widely separated and binary mixtures placed close to their components. Further, the way that taste quality is represented by the firing rate envelope is consistent across the population of cells. Thus, the temporal characteristics of responses in the population of NTS neurons, especially those that are more broadly tuned, produce a comprehensive and logical representation of the taste world.
大脑中感觉神经元的感受野通常局限于整个刺激域的一部分。然而，在味觉神经轴的各个水平上，都有许多细胞具有广泛的调谐特性，即它们对每种基本味觉品质（甜、酸、咸和苦）都有良好的反应。尽管这种广泛的调谐特性似乎排除了这些细胞在表征味觉空间方面的主要作用，但我们在此展示了相反的情况——也就是说，它们反应中味觉物质特异性的时间特征（放电率包络和峰电位时间）使每个细胞都能表征整个刺激域。具体而言，我们记录了孤束核（NTS）中细胞对四种基本味觉品质及其二元混合物代表物的反应模式。我们分析了这些反应的时间特征，并利用它们的异同来构建每个神经元所代表的味觉空间。我们发现，对于NTS中调谐更广泛的神经元，味觉空间是整个味觉域的系统表征。也就是说，这些调谐广泛的神经元的味觉空间是三维的，基本味觉品质相距甚远，二元混合物则靠近其成分放置。此外，放电率包络对味觉品质的表征方式在细胞群体中是一致的。因此，NTS神经元群体反应的时间特征，尤其是那些调谐更广泛的神经元的时间特征，产生了对味觉世界的全面且合乎逻辑的表征。
