Network Dynamics Underlying the Formation of Sparse, Informative Representations in the Hippocampus
Network Dynamics Underlying the Formation of Sparse, Informative Representations in the Hippocampus
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DOI：
10.1523/jneurosci.4261-08.2008
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发表时间：
2008-12-24
影响因子：
5.3
通讯作者：
Frank, Loren M.
中科院分区：
文献类型：
--
作者：
Karlsson, Mattias P.;Frank, Loren M.
在发育过程中，依赖活动的过程增加了神经对刺激反应的特异性，但这种类型的过程在成年可塑性中所起的作用尚不清楚。我们研究了动物学习新环境时海马体活动的动态，以了解神经选择性如何随着经验的变化而变化。当动物位于其环境的特定分区时，海马主神经元就会被激发，在任何给定的环境中，海马区的代表都是稀疏的：在CA1和CA3区，不到一半的神经元是活跃的，而其余的基本上是沉默的。在这里，我们表明不同的动力学控制这种稀疏性在CA1和上游区域CA3的演变。与熟悉的环境相比，CA1，而不是CA3，在小说中产生的尖峰电流是普通环境的两倍。在随后的休息期中，这种高速率发射在尖锐的波纹事件期间持续。随着环境的熟悉和任务绩效的提高，总的CA1种群比率下降，活跃细胞的数量减少，但不同神经元的比率下降并不均匀。相反，具有类似于12赫兹的初始峰值空间速率的细胞的活性被增强，而具有较低初始峰值速率的细胞的活性被抑制。这些变化的结果是，活跃的CA1群体由一组相对较小的具有强烈空间调节的细胞组成。这一过程在CA3中并不明显，这表明在CA1中有一个特定区域和长时间尺度的过程，以创建一个稀疏的、空间信息丰富的神经元群体。
During development, activity-dependent processes increase the specificity of neural responses to stimuli, but the role that this type of process plays in adult plasticity is unclear. We examined the dynamics of hippocampal activity as animals learned about new environments to understand how neural selectivity changes with experience. Hippocampal principal neurons fire when the animal is located in a particular subregion of its environment, and in any given environment the hippocampal representation is sparse: less than half of the neurons in areas CA1 and CA3 are active whereas the rest are essentially silent. Here we show that different dynamics govern the evolution of this sparsity in CA1 and upstream area CA3. CA1, but not CA3, produces twice as many spikes in novel compared with familiar environments. This high rate firing continues during sharp wave ripple events in a subsequent rest period. The overall CA1 population rate declines and the number of active cells decreases as the environment becomes familiar and task performance improves, but the decline in rate is not uniform across neurons. Instead, the activity of cells with initial peak spatial rates above similar to 12 Hz is enhanced, whereas the activity of cells with lower initial peak rates is suppressed. The result of these changes is that the active CA1 population comes to consist of a relatively small group of cells with strong spatial tuning. This process is not evident in CA3, indicating that a region-specific and long timescale process operates in CA1 to create a sparse, spatially informative population of neurons.