Spatial information processing in the avian hippocampus

空间认知(感知、操作和回忆有关空间环境的信息的能力)对任何物种的生存都至关重要。因此，大量研究对这种重要的认知形式进行了研究，主要集中在哺乳动物身上。这项研究表明，海马体结构(HF)和周围的皮质结构对这种学习至关重要。鸟类还有能力解决高级(如食物缓存)和在许多情况下具有独特挑战性(如迁徙)的空间问题。尽管可以在鸟类身上观察到复杂的空间技能，但相对于哺乳动物，人们对鸟类空间学习的神经基础知之甚少。虽然我们知道鸟类有HF，而且HF的损伤会在两类动物中产生类似的空间处理缺陷，但在鸟类HF中空间信息是如何处理的在很大程度上仍不清楚。这在一定程度上是因为鸟类的HF缺乏许多哺乳动物HF的定义特征，包括清晰的三板层结构和以单向为主的三突触环。事实上，即使是鸟类HF的细分也仍然是一个有争议的问题。我们也许能够通过根据其功能同源性而不是解剖学同源性来定义禽类HF的区域来解决这个问题。有许多实验范式可以使哺乳动物(即CA1、CA3和齿状回)的HF的活动模式发生分歧。在经过可比范例训练的鸟类中，探测鸟类HF广泛区域的依赖于活动的基因表达，可能为鸟类如何处理空间信息提供关键的洞察。

Spatial cognition (the ability to perceive, operate on, and recall information about spatial environments) is critical to the survival of any species. Accordingly, a wealth of research has investigated this vital form of cognition, focusing largely on mammals. This research shows that the hippocampal formation (HF) and surrounding cortical structures are critical for this kind of learning. Avian species also have the ability to solve advanced (e.g., food caching) and in many cases uniquely challenging (e.g., migration) spatial problems. Despite the sophisticated spatial repertoire that can be observed in birds, relatively little is known about the neural substrate of spatial learning in birds relative to mammals. While we know that birds have a HF and that lesions to the HF produce comparable deficits in spatial processing in both classes of animal, how spatial information is processed within the avian HF remains largely unknown. This is in part because the avian HF lacks many of the defining features of its mammalian counterpart, including clear trilaminar structure and a dominantly unidirectional tri-synaptic loop. In fact, even the subdivisions of the avian HF remain a matter of debate. We may be able to resolve this issue by defining the regions of the avian HF on the basis of their functional, rather than anatomical, homology. There are many experimental paradigms in which the pattern of activity in the HF of mammals (i.e., CA1, CA3, and the dentate gyrus) can be made to diverge. Probing activity-dependent gene expression across widespread regions of the avian HF in birds that are trained on comparable paradigms may provide critical insight into how avian species process spatial information.