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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?

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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 that cross the midline, namely:

  1. Anterior commissure, connecting the two olfactory bulbs and the temporal cortices;
  2. Hippocampal commissure (psalterium), connecting the two hippocampal formations;
  3. Habenular commissure, connecting the habenular nuclei;
  4. 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 and b. Meynert's commissure, connecting the two suprachiasmatic nuclei*).


Below figure shows the corpus callosum and the anterios commissure:

anterior commissure
Saggital section through the human brain showing the corpus callosum and anterior commissure. Source: Brain Atlas.

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

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    $\begingroup$ Actually there are five commissures, not only one. But then the hemispheres are also indirectly connected through their connections with the non-telencephalic parts of the brain. $\endgroup$ – user3116 Aug 5 '15 at 10:36
  • $\begingroup$ @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. $\endgroup$ – AliceD Aug 5 '15 at 10:38
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    $\begingroup$ See en.wikipedia.org/wiki/Commissure // "vertical": yes, but since I don't know what Max has in mind, I thought I'd mention these, since they do carry effects from one hemisphere to the other and so allow "interaction" (as specified in the question). $\endgroup$ – user3116 Aug 5 '15 at 10:58
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    $\begingroup$ @what - how about this edit? Thanks for your comment! Great. $\endgroup$ – AliceD Aug 5 '15 at 11:16

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