Last week we talked about hippocampal variability in the hippocampal head.

The hippocampal tail is another area of the hippocampus that can vary anatomically across individuals

#SubfieldWednesday (1/n)
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).

#SubfieldWednesday (2/n) Hippocampal tail is outlined in purple on T1 and T2 weightedHand drawn depiction of the hippocampus with the head, body,
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).

#SubfieldWednesday (3/n) coronal slice of hippocampal tail on ex vivo MRI. from FigurSagittal slice of hippocampus (T2 MRI) submitted by Thomas SCoronal slice of hippocampal tail (taken from ex vivo MRI) s
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)

#SubfieldWednesday (4/n) Coronal slices of the hippocampus from The "BigBrain&qu
.@RobindeFlores @david_berron @lemwisse and colleagues showed that sometimes the tail is more “curvey” and sometimes it is “straighter”.

#SubfieldWednesday (5/n) Three examples of the hippocampus (3d rendered from ex vivo
What about hippocampal subfields in the tail?

Yes, there are different subfields in the tail! Examples include the paper by De Flores (2019), Winterburn (2013) and Dalton below.

#SubfieldWednesday (6/n) Winterburn (2013) shows the subfields along the long axis ofThe hippocampal subfields are labeled on in vivo MRI along t
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).

#SubfieldWednesday (7/n) T1 and T2 MRI with subfield labels.  The hippocampal subfiel
That's it for this week! Do you have any more questions about anatomical variability in the medial temporal lobe? If so, send them along! ❓🧠❓

We are planning to host an "Ask me anything" session in the coming weeks! Stay tuned for more details! 😎

#SubfieldWednesdsay (end)
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More from @hipposubfields

5 May
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. 🍤🤓📢

#SubfieldWednesday (1/n)
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.

#SubfieldWednesday (2/n) Figure 1 from https://doi.org/10.1038/nrn.2015.24 a| A schem
Now what about those “hippocampal digitations” ?

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.

#SubfieldWednesday (3/n) Figure 2A from https://doi.org/10.1002/cne.23786  HippocampaFigure 1B from https://doi.org/10.1016/j.neuroimage.2017.11.
Read 7 tweets
14 Apr
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

#SubfieldWednesday (1/n)
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.

#SubfieldWednesday (2/n) Coronal plane from a T2 MRI depicting the canonical C shape
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.

#SubfieldWednesday (3/n)
Read 10 tweets
10 Feb
We are pleased to announce that today we have a guest #SubfieldWednesdsay 🧵 from @MarkCembrowski !

Check it out below!

(1/n)
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?

#SubfieldWednesdsay (2/n) Image courtesy of the Cembrowski lab: https://www.cembrowski
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.

#SubfieldWednesdsay (3/n) Image courtesy of Erik Bloss
Read 10 tweets
17 Dec 20
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. 🍤❣️

#SubfieldWednesday (1/n)
In our 2015 paper (Yushkevich et al., NeuroImage, 2015), we provided a list of common atlases used for hippocampal subfield definition across labs.

#SubfieldWednesday (2/n) Table 2 from http://dx.doi.org/10.1016/j.neuroimage.2015.01.
One of the most commonly used atlases cited was:

Duvernoy, H. M. (2005). The human hippocampus: functional anatomy, vascularization and serial sections with MRI. Springer Science & Business Media.

#SubfieldWednesday (3/n)
Read 10 tweets
9 Dec 20
This week I thought I would share some terminology that you may or may not know!

#SubfieldWednesday (1/n)
Most of our followers probably already know how that the name "hippocampus" means "seahorse" in Greek.

#SubfieldWednesday (2/n) https://www.wbur.org/npr/505754756/the-seahorse-in-your-brai
What do you think? When it's dissected like this, I can definitely see the similarity!

#SubfieldWednesday (3/n) Hippocampus removed from the brain (left), in comparison to
Read 8 tweets
25 Nov 20
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. 🍤🔬

#SubfieldWednesday (1/n)
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? 🤔

#SubfieldWednesday (2/n) Five different screenshots of histology slices of five diffe
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.

#SubfieldWednesday (3/n)
Read 12 tweets

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