Department of Psychology, Binghamton University, Binghamton, NY 13902-6000, USA.
J Neurophysiol. 2011 Apr;105(4):1889-96. doi: 10.1152/jn.00836.2010. Epub 2011 Feb 9.
Recent studies have provided evidence that temporal coding contributes significantly to encoding taste stimuli at the first central relay for taste, the nucleus of the solitary tract (NTS). However, it is not known whether this coding mechanism is also used at the next synapse in the central taste pathway, the parabrachial nucleus of the pons (PbN). In the present study, electrophysiological responses to taste stimuli (sucrose, NaCl, HCl, and quinine) were recorded from 44 cells in the PbN of anesthetized rats. In 29 cells, the contribution of the temporal characteristics of the response to the discrimination of various taste qualities was assessed. A family of metrics that quantifies the similarity of two spike trains in terms of spike count and spike timing was used. Results showed that spike timing in 14 PbN cells (48%) conveyed a significant amount of information about taste quality, beyond what could be conveyed by spike count alone. In another 14 cells (48%), the rate envelope (time course) of the response contributed significantly more information than spike count alone. Across cells there was a significant correlation (r = 0.51; P < 0.01) between breadth of tuning and the proportion of information conveyed by temporal dynamics. Comparison with previous data from the NTS (Di Lorenzo PM and Victor JD. J Neurophysiol 90: 1418-31, 2003 and J Neurophysiol 97: 1857-1861, 2007) showed that temporal coding in the NTS occurred in a similar proportion of cells and contributed a similar fraction of the total information at the same average level of temporal precision, even though trial-to-trial variability was higher in the PbN than in the NTS. These data suggest that information about taste quality conveyed by the temporal characteristics of evoked responses is transmitted with high fidelity from the NTS to the PbN.
最近的研究表明，时间编码在味觉的第一个中枢中继，孤束核（NTS），对味觉刺激的编码中起着重要作用。然而，在下一个味觉中枢通路，脑桥臂旁核（PbN）中的突触处是否也使用这种编码机制尚不清楚。在本研究中，我们记录了麻醉大鼠 PbN 中的 44 个细胞对味觉刺激（蔗糖、NaCl、HCl 和奎宁）的电生理反应。在 29 个细胞中，评估了响应的时间特性对各种味觉质量区分的贡献。我们使用了一套度量标准，该标准根据尖峰计数和尖峰时间来量化两个尖峰序列的相似性。结果表明，在 14 个 PbN 细胞（48%）中，尖峰时间传递了大量关于味觉质量的信息，超出了仅通过尖峰计数可以传递的信息。在另外 14 个细胞（48%）中，响应的率包络（时间历程）比仅尖峰计数单独贡献了更多的信息。在细胞之间，调谐的宽度与时间动态传递的信息比例之间存在显著的相关性（r = 0.51；P < 0.01）。与来自 NTS 的先前数据（Di Lorenzo PM 和 Victor JD。J Neurophysiol 90: 1418-31, 2003 和 J Neurophysiol 97: 1857-1861, 2007）的比较表明，在 NTS 中发生的时间编码在相似比例的细胞中发生，并在相同的平均时间精度水平下贡献了相同的总信息分数，尽管在 PbN 中比在 NTS 中更高。这些数据表明，从 NTS 到 PbN 以高保真度传递了由诱发反应的时间特征传达的关于味觉质量的信息。
