Stapleton Jennifer R, Lavine Michael L, Nicolelis Miguel A L, Simon Sidney A
Department of Neurobiology, Duke University, Durham, NC 27710, USA.
Front Neurosci. 2007 Oct 15;1(1):161-74. doi: 10.3389/neuro.01.1.1.012.2007. eCollection 2007 Nov.
The gustatory cortex (GC) processes chemosensory and somatosensory information and is involved in learning and anticipation. Previously we found that a subpopulation of GC neurons responded to tastants in a single lick (Stapleton et al., 2006). Here we extend this investigation to determine if small ensembles of GC neurons, obtained while rats received blocks of tastants on a fixed ratio schedule (FR5), can discriminate between tastants and their concentrations after a single 50 muL delivery. In the FR5 schedule subjects received tastants every fifth (reinforced) lick and the intervening licks were unreinforced. The ensemble firing patterns were analyzed with a Bayesian generalized linear model whose parameters included the firing rates and temporal patterns of the spike trains. We found that when both the temporal and rate parameters were included, 12 of 13 ensembles correctly identified single tastant deliveries. We also found that the activity during the unreinforced licks contained signals regarding the identity of the upcoming tastant, which suggests that GC neurons contain anticipatory information about the next tastant delivery. To support this finding we performed experiments in which tastant delivery was randomized within each block and found that the neural activity following the unreinforced licks did not predict the upcoming tastant. Collectively, these results suggest that after a single lick ensembles of GC neurons can discriminate between tastants, that they may utilize both temporal and rate information, and when the tastant delivery is repetitive ensembles contain information about the identity of the upcoming tastant delivery.
味觉皮层（GC）处理化学感觉和躯体感觉信息，并参与学习和预期过程。此前我们发现，GC神经元的一个亚群对单次舔舐中的味觉刺激有反应（斯台普顿等人，2006年）。在此，我们扩展这项研究，以确定在大鼠按固定比率时间表（FR5）接受成组味觉刺激时获得的GC神经元小集群，在单次给予50微升味觉刺激后，是否能够区分不同的味觉刺激及其浓度。在FR5时间表中，实验对象每第五次（强化）舔舐时接受味觉刺激，中间的舔舐不给予强化。使用贝叶斯广义线性模型分析集群放电模式，其参数包括放电频率和尖峰序列的时间模式。我们发现，当同时纳入时间和频率参数时，13个集群中有12个正确识别了单次味觉刺激的给予。我们还发现，未强化舔舐期间的活动包含有关即将到来的味觉刺激的身份信息，这表明GC神经元包含有关下一次味觉刺激给予的预期信息。为支持这一发现，我们进行了实验，在每个组内随机给予味觉刺激，发现未强化舔舐后的神经活动无法预测即将到来的味觉刺激。总体而言，这些结果表明，单次舔舐后，GC神经元集群能够区分不同的味觉刺激，它们可能利用时间和频率信息，并且当味觉刺激的给予是重复性的时，集群包含有关即将到来的味觉刺激给予的身份信息。
