This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Dr. Martin Wessendorf is a neuroscientist and an associate professor emeritus at the University of Minnesota.
His work focuses on how the brainstem controls the function of neurons in the spinal cord. Daniel Wang also researches the brain, focusing on cognitive neuroscience and neurodegenerative diseases. They are the authors of a new article in Frontiers in Neuroanatomy that explores several brain circuits in four-limbed animals that are cross-wired (meaning one side of the brain connects with the opposite side of the body).
It proposes a novel hypothesis about how they might have evolved. If you've studied neuroanatomy, you might have wondered about the brain's cross-wiring and its evolutionary history. We'll go over different pathways and then propose our hypothesis on why most of these contralateral (midline-crossing) pathways evolved.
The story begins with sensory input from the eyes. Because the lens of the eye reverses the image on the retina, what the eye sees to the right of us forms an image on the left side of the retina and vice versa. The optic nerve carries this information to the optic chiasm, where the nerve fibers responsible for the right visual field are separated out and directed to the left half of the brain.
This process is mirrored for the left visual field. Our visual inputs target, among other things, an ancient structure called the optic tectum. The optic tectum (which in mammals is called the superior colliculus) is a structure in the midbrain that generates rapid responses to what we see.
Information from each visual field is mapped to the opposite side of the optic tectum. In its deeper layers, physical sensations (somatosensory information) are mapped as well. The optic tectum is present in all vertebrate species and, as a result, appears to be among the oldest neuroanatomical structures in vertebrates.
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