<p>The <em>corpus callosum</em> is a massive horizontal white matter tract (commissure) that connects the two hemispheres and it is considered the most important route of communication between the hemispheres. </p>

<p>However, there are <a href="http://radiopaedia.org/articles/commissures-of-the-brain" rel="nofollow noreferrer">five additional commissures</a> that cross the midline, namely:</p>

<ol>
<li><a href="http://www.anatomyatlases.org/MicroscopicAnatomy/Section17/Plate17344.shtml" rel="nofollow noreferrer">Anterior commissure</a>, connecting the two olfactory bulbs and the temporal cortices;</li>
<li><a href="https://www.msu.edu/user/brains/brains/sheep/glossary/hippocampalcommissure.html" rel="nofollow noreferrer">Hippocampal commissure</a> (psalterium), connecting the two hippocampal formations;</li>
<li><a href="https://en.wikipedia.org/wiki/Habenular_commissure" rel="nofollow noreferrer">Habenular commissure</a>, connecting the habenular nuclei; </li>
<li><a href="https://en.wikipedia.org/wiki/Posterior_commissure" rel="nofollow noreferrer">Posterior commissure</a>, connecting the pretectal nuclei, mediating the consensual pupillary light reflex;</li>
<li>Supraoptic commissures (a. <a href="https://en.wikipedia.org/wiki/Ventral_supraoptic_decussation" rel="nofollow noreferrer">Gudden's commissure, or ventral supraoptic decussation connecting the medial geniculate bodies</a> and b. <a href="http://www.sciencedirect.com/science/article/pii/0006899375903224" rel="nofollow noreferrer">Meynert's commissure</a>, connecting the two suprachiasmatic nuclei<sup>*</sup>). </li>
</ol>

<p><br>
Below figure shows the corpus callosum and the anterios commissure:</p>

<p><a href="https://i.sstatic.net/2hEy8.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/2hEy8.jpg" alt="anterior commissure"></a><br>
<sup>Saggital section through the human brain showing the <em>corpus callosum</em> and <em>anterior commissure</em>. Source: <a href="http://www.anatomyatlases.org/MicroscopicAnatomy/Section17/Plate17344.shtml" rel="nofollow noreferrer">Brain Atlas</a>.</sup></p>

<p><sup>*The exact connection of Meynert's commissure I am unsure of. This is the best I could do.</sup> </p>

CC BY-SA 3.0
2015-08-05T10:38:12.980Z
@what - 5?! I didn't know that. The brain indeed connects via the pons etc, but those connections are generally considered to carry vertical tracts, not horizontal ones.
AliceD
CC BY-SA 3.0
2015-08-05T11:16:30.630Z
@what - how about this edit? Thanks for your comment! Great.
AliceD
CC BY-SA 3.0
2015-08-04T14:57:47.963Z
2015-08-05T13:14:05.500Z
2015-08-05T13:14:05.500Z
AliceD
<p>Are the human cerebral hemispheres only connected via the <em>corpus callosum</em>? Or is there any other structure for interaction between the left and right hemispheres?</p>

<neuroscience><neuroanatomy>
Are the human cerebral hemispheres only connected via the corpus callosum?
max
# Are the human cerebral hemispheres only connected via the corpus callosum?

(Asked by: username_0 on 2015-08-04)

Are the human cerebral hemispheres only connected via the *corpus callosum*? Or is there any other structure for interaction between the left and right hemispheres?

**Tags:** neuroscience, neuroanatomy


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## 1 answers

### Answer by username_1 on 2015-08-04. Score: 7

The *corpus callosum* is a massive horizontal white matter tract (commissure) that connects the two hemispheres and it is considered the most important route of communication between the hemispheres.

However, there are [five additional commissures](http://radiopaedia.org/articles/commissures-of-the-brain) that cross the midline, namely:

1. [Anterior commissure](http://www.anatomyatlases.org/MicroscopicAnatomy/Section17/Plate17344.shtml), connecting the two olfactory bulbs and the temporal cortices;
2. [Hippocampal commissure](https://www.msu.edu/user/brains/brains/sheep/glossary/hippocampalcommissure.html) (psalterium), connecting the two hippocampal formations;
3. [Habenular commissure](https://en.wikipedia.org/wiki/Habenular_commissure), connecting the habenular nuclei;
4. [Posterior commissure](https://en.wikipedia.org/wiki/Posterior_commissure), connecting the pretectal nuclei, mediating the consensual pupillary light reflex;
5. Supraoptic commissures (a. [Gudden's commissure, or ventral supraoptic decussation connecting the medial geniculate bodies](https://en.wikipedia.org/wiki/Ventral_supraoptic_decussation) and b. [Meynert's commissure](http://www.sciencedirect.com/science/article/pii/0006899375903224), connecting the two suprachiasmatic nuclei\*).

Below figure shows the corpus callosum and the anterios commissure:

[![anterior commissure](https://i.sstatic.net/2hEy8.jpg)](https://i.sstatic.net/2hEy8.jpg)  
Saggital section through the human brain showing the *corpus callosum* and *anterior commissure*. Source: [Brain Atlas](http://www.anatomyatlases.org/MicroscopicAnatomy/Section17/Plate17344.shtml).

\*The exact connection of Meynert's commissure I am unsure of. This is the best I could do.

> **Comments:**
> **username_1**: @what - 5?! I didn't know that. The brain indeed connects via the pons etc, but those connections are generally considered to carry vertical tracts, not horizontal ones.  
> **username_1**: @what - how about this edit? Thanks for your comment! Great.  

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