Division of Oral Biology, College of Dentistry, the Ohio State University, Columbus, Ohio, United States of America.
PLoS One. 2013 Oct 4;8(10):e76828. doi: 10.1371/journal.pone.0076828. eCollection 2013.
It has been demonstrated that temporal features of spike trains can increase the amount of information available for gustatory processing. However, the nature of these temporal characteristics and their relationship to different taste qualities and neuron types are not well-defined. The present study analyzed the time course of taste responses from parabrachial (PBN) neurons elicited by multiple applications of "sweet" (sucrose), "salty" (NaCl), "sour" (citric acid), and "bitter" (quinine and cycloheximide) stimuli in an acute preparation. Time course varied significantly by taste stimulus and best-stimulus classification. Across neurons, the ensemble code for the three electrolytes was similar initially but quinine diverged from NaCl and acid during the second 500 ms of stimulation and all four qualities became distinct just after 1s. This temporal evolution was reflected in significantly broader tuning during the initial response. Metric space analyses of quality discrimination by individual neurons showed that increases in information (H) afforded by temporal factors was usually explained by differences in rate envelope, which had a greater impact during the initial 2s (22.5% increase in H) compared to the later response (9.5%). Moreover, timing had a differential impact according to cell type, with between-quality discrimination in neurons activated maximally by NaCl or citric acid most affected. Timing was also found to dramatically improve within-quality discrimination (80% increase in H) in neurons that responded optimally to bitter stimuli (B-best). Spikes from B-best neurons were also more likely to occur in bursts. These findings suggest that among PBN taste neurons, time-dependent increases in mutual information can arise from stimulus- and neuron-specific differences in response envelope during the initial dynamic period. A stable rate code predominates in later epochs.
已有研究表明，尖峰神经元发放时间特性的改变可以增加味觉处理过程中的信息量。然而，这些时间特性的本质及其与不同味觉质量和神经元类型的关系尚未明确界定。本研究在急性脑片制备条件下，分析了多轮给予“甜”（蔗糖）、“咸”（NaCl）、“酸”（柠檬酸）和“苦”（奎宁和环己亚硝脲）刺激后，臂旁核（PBN）神经元的味觉反应时程。味觉刺激和最佳刺激分类对时程的影响显著不同。在所有神经元中，三种电解质的集合编码在初始阶段相似，但奎宁在刺激的后 500ms 与 NaCl 和酸分离，所有四种味觉在 1s 后变得完全不同。这种时间演化反映在初始反应中明显更宽的调谐。个体神经元的质量辨别度量空间分析表明，时间因素增加的信息（H）通常可以通过速率包络的差异来解释，在最初的 2s（H 增加 22.5%）中，速率包络的影响比后期反应（9.5%）更大。此外，根据细胞类型，时间的影响也不同，NaCl 或柠檬酸激活的神经元之间的质量辨别受影响最大。在对苦味刺激（B-最佳）反应最佳的神经元中，时间也显著提高了质量内辨别（H 增加 80%）。对 B-最佳神经元的反应中，更多的尖峰发生在爆发中。这些发现表明，在臂旁核味觉神经元中，在初始动态期内，刺激和神经元特异性的反应包络差异可以引起依赖时间的互信息增加。在后期阶段，稳定的速率编码占主导地位。
