Which structure connects the left and right hemispheres of the brain?

The corpus callosum is the primary structure that connects the left and right hemispheres of the brain, facilitating communication between them. It is a large bundle of neural fibers that allows for the transfer of information and coordination of activities between the two hemispheres.

Specifically, the genu of the corpus callosum refers to the anterior portion, while the splenium is the posterior part. While both the genu and splenium are components of the corpus callosum and play important roles, the answer highlights the corpus callosum as the overall structure that serves this function.

In contrast, optic radiation refers to the visual pathway from the lateral geniculate nucleus of the thalamus to the visual cortex and is not involved in interhemispheric communication. The primary motor cortex is responsible for planning and executing voluntary movements and is localized to each hemisphere, without direct connectivity functions.