Larkin Margaret Carr, Lykken Christine, Tye Lynne D, Wickelgren Jeanette Graham, Frank Loren M
Center for Integrative Neuroscience and Department of Physiology, University of California, San Francisco, San Francisco, California.
Hippocampus. 2014 Jul;24(7):773-83. doi: 10.1002/hipo.22268. Epub 2014 Mar 21.
Animals display an innate preference for novelty, spending more time exploring both novel objects and familiar objects in novel locations. This increase in exploration is thought to allow the animal to gather the information necessary to encode new experiences. Despite extensive evidence that increased exploration following spatial change requires the hippocampus, the pattern of hippocampal activity that supports this behavior remains unknown. We examined activity in hippocampal output area CA1 and one synapse upstream in area CA3 while freely behaving rats performed an object-place recognition task. We found that the presence of novelty substantially altered activity in CA1, but not in CA3. During exploration of displaced familiar objects and novel objects in unexpected locations, CA1 place cells showed robust increases in firing rate. These firing rate increases persisted during sharp wave ripples, when place cell representations of previous experiences are replayed. Unexpectedly, increases in CA1 activity were not spatially restricted to regions of the environment that underwent change, indicating a generalized novelty signal. We suggest that hippocampal area CA1 broadcasts the presence of novelty, rather than signaling what is novel, and simultaneously becomes more plastic, allowing the integration of new information into previously stored memories.
动物表现出对新奇事物的先天偏好，会花更多时间探索新奇物体以及处于新位置的熟悉物体。这种探索行为的增加被认为能让动物收集编码新体验所需的信息。尽管有大量证据表明空间变化后探索行为的增加需要海马体参与，但支持这种行为的海马体活动模式仍不清楚。我们在自由活动的大鼠执行物体 - 位置识别任务时，检测了海马输出区域CA1以及CA3区上游一个突触处的活动。我们发现新奇事物的存在显著改变了CA1区的活动，但CA3区没有。在探索移到新位置的熟悉物体和处于意外位置的新奇物体时，CA1区的位置细胞放电频率显著增加。当回放先前经历的位置细胞表征时，这些放电频率的增加在尖波涟漪期间持续存在。出乎意料的是，CA1区活动的增加在空间上并不局限于环境发生变化的区域，这表明存在一种普遍的新奇信号。我们认为海马体CA1区传递的是新奇事物的存在，而非表明什么是新奇的，并且同时变得更具可塑性，从而允许将新信息整合到先前存储的记忆中。
