Lemon Christian H, Smith David V
Department of Anatomy and Neurobiology, University of Tennessee Health Science Center, Memphis, Tennessee 38163, USA.
J Neurosci. 2006 Jul 12;26(28):7433-43. doi: 10.1523/JNEUROSCI.0106-06.2006.
We explored how variability in responding to taste stimuli could impact the signaling of taste quality information by neuron types and individual cells in the nucleus of the solitary tract. One hundred sixty-two neurons recorded from anesthetized rats were grouped using multivariate analysis of taste responses to the following (in m): 0.5 sucrose, 0.1 NaCl, 0.01 HCl, and 0.01 quinine-HCl. Neurons fell into one of three groups corresponding to cell types that responded optimally to sucrose, NaCl, or HCl. A statistical model was used to examine whether responses observed among neurons within each group could be correctly attributed to the optimal stimulus or another tastant on the basis of spike count. Results revealed poor classification performance in some cases attributable to wide variations in the sensitivities of neurons that compose a cell type. This outcome leads us to question whether neuron types could faithfully encode a single taste quality. We then theoretically explored whether a hypothetical observer of individual neurons could discriminate between spiking rates to different tastants during the first second of stimulus processing. Spike rate was found to be an unreliable predictor of stimulus quality for each neuron tested. However, additional analyses suggested that taste stimuli could be identified by a reader that attends to the relative spiking activities of different kinds of neurons in parallel. Rather than assigning meaning to individual neurons or categories of them, central gustatory circuits may signal quality information using a strategy that involves the relative activities of neurons with different sensitivities to tastants.
我们探究了对味觉刺激反应的变异性如何影响孤束核中神经元类型和单个细胞对味觉质量信息的信号传递。从麻醉大鼠身上记录的162个神经元，通过对以下味觉反应（单位：毫摩尔）进行多变量分析进行分组：0.5蔗糖、0.1氯化钠、0.01盐酸和0.01盐酸奎宁。神经元分为三组，分别对应对蔗糖、氯化钠或盐酸反应最佳的细胞类型。使用统计模型来检验每组内神经元的反应是否能基于脉冲计数正确归因于最佳刺激或另一种味觉物质。结果显示，在某些情况下分类表现不佳，这归因于构成一种细胞类型的神经元敏感性存在广泛差异。这一结果使我们质疑神经元类型是否能忠实地编码单一味觉质量。然后，我们从理论上探究了单个神经元的假设观察者在刺激处理的第一秒内是否能区分对不同味觉物质的放电频率。结果发现，对于每个测试的神经元，放电频率都是刺激质量的不可靠预测指标。然而，进一步的分析表明，一个关注不同类型神经元相对放电活动的读取器可以识别味觉刺激。中枢味觉回路可能并非赋予单个神经元或其类别以意义，而是使用一种涉及对味觉物质具有不同敏感性的神经元相对活动的策略来传递质量信息。
