Fogwe Leslie A., Reddy Vamsi, Mesfin Fassil B.
University of Missouri Columbia
McKinsey & Company
The hippocampus is the "flash drive" of the human brain and is often associated with memory consolidation and decision-making, but it is far more complex in structure and function than a flash drive. The hippocampus is a convex elevation of gray matter tissue within the parahippocampal gyrus inside the inferior temporal horn of the lateral ventricle. One can describe it more holistically as a curved and recurved sheet of the cortex that folds into the temporal lobe's medial surface. The hippocampus has three distinct zones: the dentate gyrus, the hippocampus proper, and the subiculum. The subiculum is positioned between the hippocampus proper and entorhinal and other cortices. The parahippocampal gyrus and cingulate sulci are located on the medial surface of the hemisphere, forming a C-shaped ring. The medial temporal lobe cortex includes major subdivisions, such as the hippocampus and the entorhinal cortex. This five-centimeter-long hippocampus (from the anterior end at the amygdala to the posterior end near the splenium of the corpus callosum) divides into a head, body, and tail. the head is expanded and bears two or three shallow grooves called pes hippocampi. The head of the hippocampus is part of the posterior half of the triangular uncus and is separated inferiorly from the parahippocampal gyrus by the uncal sulcus. The alveus, which is the surface of the hippocampus, is covered by the ependymal inside the ventricular cavity. The fornix, which is the main outflow bundle out of the hippocampus, wraps around the thalamus, where it then becomes separated by the choroidal fissure and the choroid plexus. The hippocampus contains parts like the fimbria, crus, body, and column—the fimbria forms where alveus fibers converge along the medial portion of the lateral ventricle's inferior horn. The white matter of the fimbria separates to form a crux of the ipsilateral fornix at a point beyond the splenium of the corpus callosum. The Cornu Ammonis (CA) is a seahorse-like or ram's horn-like structure that describes the different layers of the hippocampus. There are four hippocampal subfields CA1, CA2, CA3, and CA4. CA3 and CA2 border the hilus of the dentate gyrus on either side. CA3 is the largest in the hippocampus and receives fibers from the dentate granule cells on their proximal dendrites. The pyramidal cell layer is about ten cells thick.
海马体是人类大脑的“闪存盘”，常与记忆巩固和决策相关联，但其结构和功能远比闪存盘复杂得多。海马体是侧脑室颞下角内海马旁回内灰质组织的一个凸隆起。可以更全面地将其描述为折叠进颞叶内表面的一层弯曲且弯折的皮质。海马体有三个不同的区域：齿状回、海马本部和下托。下托位于海马本部与内嗅皮质及其他皮质之间。海马旁回和扣带沟位于半球的内表面，形成一个C形环。颞叶内侧皮质包括主要的亚区，如海马体和内嗅皮质。这个五厘米长的海马体（从杏仁核处的前端到胼胝体压部附近的后端）分为头、体和尾。头部膨大，有两三条浅沟，称为海马足。海马体的头部是三角形钩回后半部的一部分，在下方通过钩回沟与海马旁回分开。海马体表面的脑室膜在脑室腔内被室管膜覆盖。穹窿是海马体的主要传出束，环绕丘脑，然后在那里被脉络膜裂和脉络丛分隔开。海马体包含如伞、脚、体和柱等部分——伞在脑室膜纤维沿侧脑室下角内侧部分汇聚处形成。伞的白质在胼胝体压部之外的一点分开，形成同侧穹窿的交叉。海马结构是一个海马状或羊角状结构，描述了海马体的不同层。有四个海马亚区CA1、CA2、CA3和CA4。CA3和CA2在两侧与齿状回的门区相邻。CA3是海马体中最大的，在其近端树突上接收来自齿状颗粒细胞的纤维。锥体细胞层约有十个细胞厚。
