Department of Psychology, University of California, Los Angeles, Los Angeles, California 90095
Brain Research Institute, University of California, Los Angeles, Los Angeles, California 90095.
J Neurosci. 2021 Aug 11;41(32):6933-6945. doi: 10.1523/JNEUROSCI.0830-21.2021. Epub 2021 Jul 1.
The orbitofrontal cortex (OFC) and hippocampus share striking cognitive and functional similarities. As a result, both structures have been proposed to encode "cognitive maps" that provide useful scaffolds for planning complex behaviors. However, while this function has been exemplified by spatial coding in neurons of hippocampal regions-particularly place and grid cells-spatial representations in the OFC have been investigated far less. Here we sought to address this by recording OFC neurons from male rats engaged in an open-field foraging task like that originally developed to characterize place fields in rodent hippocampal neurons. Single-unit activity was recorded as rats searched for food pellets scattered randomly throughout a large enclosure. In some sessions, particular flavors of food occurred more frequently in particular parts of the enclosure; in others, only a single flavor was used. OFC neurons showed spatially localized firing fields in both conditions, and representations changed between flavored and unflavored foraging periods in a manner reminiscent of remapping in the hippocampus. Compared with hippocampal recordings taken under similar behavioral conditions, OFC spatial representations were less temporally reliable, and there was no significant evidence of grid tuning in OFC neurons. These data confirm that OFC neurons show spatial firing fields in a large, two-dimensional environment in a manner similar to hippocampus. Consistent with the focus of the OFC on biological meaning and goals, spatial coding was weaker than in hippocampus and influenced by outcome identity. The orbitofrontal cortex (OFC) and hippocampus have both been proposed to encode "cognitive maps" that provide useful scaffolds for planning complex behaviors. This function is exemplified by place and grid cells identified in hippocampus, the activity of which maps spatial environments. The current study directly demonstrates very similar, though not identical, spatial representatives in OFC neurons, confirming that OFC-like hippocampus-can represent a spatial map under the appropriate experimental conditions.
额眶回皮层（OFC）和海马体具有惊人的认知和功能相似性。因此，这两个结构都被提议编码“认知地图”，为规划复杂行为提供有用的支架。然而，虽然这一功能已经在海马区神经元的空间编码中得到了例证——特别是位置和网格细胞——但额眶回皮层中的空间表示形式的研究要少得多。在这里，我们试图通过记录雄性大鼠在类似于最初开发的用于描述啮齿动物海马神经元位置场的开放式觅食任务中的额眶回皮层神经元来解决这个问题。当老鼠在一个大围栏中寻找随机散布的食物颗粒时，记录单个单元的活动。在某些会话中，特定口味的食物在围栏的特定部分更频繁地出现；在其他会话中，仅使用一种口味。在这两种情况下，OFC 神经元都显示出空间局部化的发射场，并且在有味道和无味道的觅食期间，代表发生了变化，这与海马体中的重新映射方式相似。与在类似行为条件下记录的海马体记录相比，OFC 空间表示的时间可靠性较低，并且没有证据表明 OFC 神经元存在网格调谐。这些数据证实，OFC 神经元在类似于海马体的方式在一个大的二维环境中显示出空间发射场。与 OFC 对生物意义和目标的关注一致，空间编码比海马体弱，并且受结果身份的影响。额眶回皮层（OFC）和海马体都被提议编码“认知地图”，为规划复杂行为提供有用的支架。这一功能由海马体中识别的位置和网格细胞所体现，其活动映射了空间环境。当前的研究直接证明了 OFC 神经元中存在非常相似但不完全相同的空间代表，这证实了类似于 OFC 的海马体——在适当的实验条件下，可以代表空间地图。
