<p><strong>Short answer</strong><br>
Glial scarring is due to brain damage. Brain damage results in molecular signals to be released that attract glial cells. Spaces in the brain present during development are not characterized by signalling molecules associated with trauma.</p>

<p><strong>Background</strong><br>
The key here is that <a href="https://en.wikipedia.org/wiki/Glial_scar" rel="nofollow noreferrer">glial scar formation</a> follows damage to the brain, and is associated with <a href="https://en.wikipedia.org/wiki/Brain_healing" rel="nofollow noreferrer">healing processes in the brain</a>, including those occurring after ischemic stroke <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3936028/" rel="nofollow noreferrer">(Huang <em>et al</em>., 2014)</a> and physical trauma (source: <a href="https://www.sciencedaily.com/releases/2010/04/100427171804.htm" rel="nofollow noreferrer">Society for Neuroscience, 2010</a>). Brain damage results in the release of inflammatory proteins that signal glia to form scar tissue (<em>e.g.</em> <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3669736/" rel="nofollow noreferrer">Patel <em>et al</em> (2013)</a>).</p>

<p>There are many vacant spaces in the brain (Fig. 1), most notably the four <strong><a href="https://en.wikipedia.org/wiki/Ventricular_system" rel="nofollow noreferrer">ventricles</a></strong>. These spaces are there from birth, and are actually formed within the first few weeks after conception. Because there are no signals involved from brain trauma, and these structures should be there, the glial system does not get signals to invade these areas and fill them up with glial scar tissue.</p>

<p>Also note that glial cells have little to do with neurogeneration; glia is not nervous tissue.  </p>

<p><a href="https://i.sstatic.net/OwPMq.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/OwPMq.jpg" alt="ventricles"></a>
<sup>Fig. 1. Brain ventricles. source: <a href="https://www.anatomynote.com/human-anatomy/nerves-system/brain-ventricular-anatomy/" rel="nofollow noreferrer">Anatomy Note</a></sup></p>

<p><sub><strong>References</strong><br>
<strong>-</strong> <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3936028/" rel="nofollow noreferrer">Huang<em>et al</em>., <em>Int J Med Sci</em> (2014); <strong>11</strong>(4): 344–8</a><br>
<strong>-</strong> <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3669736/" rel="nofollow noreferrer">Patel <em>el al</em>., <em>Int J Physiol Pathophysiol Pharmacol</em> (2013); <strong>5</strong>(2): 73–90</a></sub></p>

CC BY-SA 3.0
2018-03-20T09:32:11.800Z
2018-03-22T10:20:48.027Z
2018-03-22T10:20:48.027Z
AliceD
<p>I understand that, generally, when a neuron dies, the vacated, empty space will form a scar in the form of an astrocyte. Basically, the astrocyte thus replaces that neuron.</p>

<p>Why then are there empty spaces around the hippocampus and striatum that aren't filled with astrocytes? I am talking about the same spaces where adult neurogenesis might occur.</p>

<p>Why are these spaces left empty? Are they "waiting" for possible adult neurogenesis and therefore don't get filled in with astrocytes?</p>

<p>A better question might be "<strong>How does the CNS distinguish between types of empty spaces inside it?</strong>"</p>

CC BY-SA 3.0
2018-01-09T11:50:57.923Z
BTW I would theorize that each time a neuron is about to die, some dyingness markers are biosynthesized and somehow cause creation of 1 astrocyte (only 1?) per dead neuron and this could explain why the aforementioned spaces aren't effected by that and aren't filled with astrocytes themselves...
Arcticooling
<neuroscience><neurogenesis><hippocampus>
Why are empty spaces around hippocampus and striatum not filled with astrocytes?
Arcticooling
# Why are empty spaces around hippocampus and striatum not filled with astrocytes?

(Asked by: username_0 on 2018-01-09)

I understand that, generally, when a neuron dies, the vacated, empty space will form a scar in the form of an astrocyte. Basically, the astrocyte thus replaces that neuron.

Why then are there empty spaces around the hippocampus and striatum that aren't filled with astrocytes? I am talking about the same spaces where adult neurogenesis might occur.

Why are these spaces left empty? Are they "waiting" for possible adult neurogenesis and therefore don't get filled in with astrocytes?

A better question might be "**How does the CNS distinguish between types of empty spaces inside it?**"

**Tags:** neuroscience, neurogenesis, hippocampus

> **Comments:**
> **username_0**: BTW I would theorize that each time a neuron is about to die, some dyingness markers are biosynthesized and somehow cause creation of 1 astrocyte (only 1?) per dead neuron and this could explain why the aforementioned spaces aren't effected by that and aren't filled with astrocytes themselves...  

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## 1 answers

### Answer by username_1 on 2018-03-20. Score: 2

**Short answer**  
Glial scarring is due to brain damage. Brain damage results in molecular signals to be released that attract glial cells. Spaces in the brain present during development are not characterized by signalling molecules associated with trauma.

**Background**  
The key here is that [glial scar formation](https://en.wikipedia.org/wiki/Glial_scar) follows damage to the brain, and is associated with [healing processes in the brain](https://en.wikipedia.org/wiki/Brain_healing), including those occurring after ischemic stroke [(Huang *et al*., 2014)](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3936028/) and physical trauma (source: [Society for Neuroscience, 2010](https://www.sciencedaily.com/releases/2010/04/100427171804.htm)). Brain damage results in the release of inflammatory proteins that signal glia to form scar tissue (*e.g.* [Patel *et al* (2013)](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3669736/)).

There are many vacant spaces in the brain (Fig. 1), most notably the four **[ventricles](https://en.wikipedia.org/wiki/Ventricular_system)**. These spaces are there from birth, and are actually formed within the first few weeks after conception. Because there are no signals involved from brain trauma, and these structures should be there, the glial system does not get signals to invade these areas and fill them up with glial scar tissue.

Also note that glial cells have little to do with neurogeneration; glia is not nervous tissue.

[![ventricles](https://i.sstatic.net/OwPMq.jpg)](https://i.sstatic.net/OwPMq.jpg)
Fig. 1. Brain ventricles. source: [Anatomy Note](https://www.anatomynote.com/human-anatomy/nerves-system/brain-ventricular-anatomy/)

**References**  
**-** [Huang*et al*., *Int J Med Sci* (2014); **11**(4): 344–8](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3936028/)  
**-** [Patel *el al*., *Int J Physiol Pathophysiol Pharmacol* (2013); **5**(2): 73–90](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3669736/)


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