But first, what do we mean by the hippocampal tail? Definitions vary, but one way to define the tail is the part of the hippocampus located posterior to the corpora quadrigemina (i.e. superior and inferior colliculi).
The hippocampal dentations that can be visualized in the hippocampal body on the sagittal plane (pointed out earlier by @thomcat992). But they can also often be seen in the coronal plane in the hippocampal tail (as shown by @lemwisse and colleagues).
That’s because of the curvature of the hippocampus—it often curves medially in the tail region. See these images from the Big Brain (@BigBrainProject) for 3D renderings that show off this curvature. (paper by @jordandekraker)
As pointed out above, the anatomy is complicated and variable across individuals in the tail. Some protocols do not label the individual subfields in the tail (e.g. FreeSurfer v6 and v7) and instead give it a single label (periwinkle color in Fig below).
Today we continue our thread series discussing anatomical variability in the medial temporal lobe (MTL). Today’s topic is anatomical variability in the hippocampal head with a focus on the hippocampal digitations. 🍤🤓📢
But first, what do we mean by the hippocampal head? We are talking about the anterior part of the hippocampus that contains or is adjacent to the uncus.
Ding & Van Hoesen (2015) describe external and internal digitations. The external digitations are the “bumps” that extend dorsally and the interior digitations are the “bumps” that extend ventrally.
Happy #SubfieldWednesday! Today we will be sharing a 🧵 on anatomical variability in the medial temporal lobe (MTL). MTL subregions vary in size and shape across individuals & these variations can make landmark identification and segmentation difficult
Today we will focus on the *most* consistent structure in the MTL: the hippocampal body. Most of our followers will be familiar with this canonical hippocampal body shape shown below in the coronal plane.
The shape is characterized by a consistent “C-shape” when viewed in the coronal plane. The C is formed by the cornu ammonus (CA) subfield on the lateral part of the hippocampal body.
When you look at a textbook diagram hippocampus, one sees a series of subfields - DG, CA3, and CA1. All of these regions have specialized properties relative to one another. But it raises the question: within each region, are the cell types uniform?
CA1 pyramidal cells of the rodent brain, one of the most studied neuron types in the brain, provide a good starting point to answer this question from both structural and functional perspectives.
Is anyone planning to do some reading about hippocampal neuroanatomy over the holidays?
If you answered, "yes", this week's #SubfieldWednesday is for you! We will give you a list of "must read" atlas references about our favorite brain structure. 🍤❣️
Hello and happy #SubfieldWednesday! Today we are going to get a bit more familiar with how the hippocampal subfields differ in their composition of different cell types, cell sizes, and layer thickness. 🍤🔬
Here are some images taken from five different hippocampal subfields (CA1, CA2, CA3, dentate gyrus, and subiculum). Can you tell which number corresponds to which subfield? 🤔
Because a Nissl stain was applied to these slices, the cell bodies appear dark purple. This allows neuroanatomists to characterize the size, shape, and relative spacing of the cells.