The large commissure that connects the right and left sides of the brain is called the

Corpus callosum

Explanation:

 The corpus callosum is one of the large type of commissure and it is one of the part of brain. The main function if the corpus callosum is that it connects the brain both the sides that is left and right of the hemisphere in the brain.

The corpus callosum are basically responsible for transmitting the neural message in both the ends of the brain.

It is also known as the red part of the brain and it is mainly responsible for manage the information flow in our mind.  

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