Functional gradients in the medial temporal memory system

神经科学面临的最大挑战之一仍然是描述持久记忆是如何在大脑中实现的。对情景记忆（对在空间和时间上展开的经历的记忆）的可处理描述的探索，由于许多原因，集中在海马的形成和周围的内侧颞叶皮层上。海马体之所以成为记忆最终“索引”的有吸引力的位置，部分证据是这个结构从整个大脑的每一种感觉模式中接收大量的收敛输入。然而，这种趋同带来了独特的挑战，因为越来越明显的是，这些不同的输入并没有得到同样有力的处理。来自不同结构的输入在记忆系统的不同部分以不同的梯度到达海马体形成，在这些输入如何影响海马体神经元大规模集合的信息表征方面产生了巨大差异的可能性。海马体记忆系统的众多功能梯度以及它们如何影响信息处理才刚刚开始被理解。目前的建议旨在通过使用活动相关基因表达评估大规模神经元群体的活动模式来进一步了解这一点。这些数据将通过几个已知的功能梯度（例如，从海马体结构的间隔到颞极以及垂直的近端远端梯度）收集。这些信息将在动物对不同性质的刺激（如奖励大小、厌恶刺激、结果概率、空间环境变化）的变化作出反应时收集。总的来说，这些研究将为理解经验的内部表征如何动态地维持、处理和存储，以及它们如何与感官输入相互作用提供关键数据。

One of the greatest challenges facing neuroscience remains the description of how lasting memory is implemented within the brain. The search for a tractable description of episodic memory (the memory for experiences that unfold over space and time) has, for many reasons, focused on the hippocampal formation and surrounding medial temporal lobe cortices. Part of the body of evidence that makes the hippocampal formation an attractive seat for the ultimate “indexing” of memories is the fact that this structure receives a huge array of convergent input in every sensory modality from across the entire brain. This very convergence, however, creates unique challenges, since it is becoming increasingly clear that these various inputs are not processed equally robustly. Input from different structures arrive to the hippocampal formation at different parts of the memory system and in different gradients, creating the potential for dramatic differences in how these inputs impact the information representations of large-scale ensembles of hippocampal neurons. The multitude of functional gradients across the hippocampal memory system and how they impact information processing is only beginning to be understood. The current proposal aims to further this understanding by assessing the pattern of activity of large-scale neuronal populations using activity-related gene expression. These data will be collected across several known functional gradients (e.g., from the septal to temporal poles of the hippocampal formation as well as the perpendicular proximodistal gradient). This information will be gathered as animals react to changes in qualitatively different types of stimuli (e.g., reward magnitude, aversive stimuli, outcome probabilities, changes in spatial surroundings). Collectively, these studies will provide critical data for understanding, in general, how internal representations of experiences are dynamically maintained, processed and stored, and how they interact with sensory input.