Do You See What I See?

By Chrissy Swartz

In a September Sound of Science (Friday afternoons at 1:04 PM on WNIJ) recording, we discussed the idea of whether a person can accurately be described as “right-brained” or “left-brained.” This concept suggests that a person’s preference for being logical or creative will indicate which hemisphere of the brain they utilize the most. This dichotomy has been debunked through study and research, but there is an anatomically interesting observation that can be made from the studies.

The control of motor functions is linked to brain hemispheres; the right side of the brain governs the left side of the body, and the left side of the brain governs the right. Most aspects of speech and communication are processed in the left hemisphere of the brain, while the right hemisphere is responsible for spatial analysis, intuition, and non-verbal processing. However, there is no definitive evidence of hemisphere dominance, and individuals who have suffered injury to one hemisphere of the brain may experience difficulties with spatial abilities and calculating simple mathematical problems at the same time – each a function of creativity and a function of logic.

Based on the prescribed pattern, one might incorrectly infer that vision functions similarly to motor control. It may seem that the right eye sends images to the left hemisphere of the brain, and the left eye sends images to the right hemisphere. However, this inference is incorrect, and the reality is quite intriguing.

The human eye requires both hemispheres of the brain to produce a complete, integrated field of vision. Light energy enters the eyes in the form of waves and once exposed to the retina, are converted to electrical energy. These electrical impulses pass through the optic nerve into the optic chiasm, where they are separated towards the left and right side of the brain. The left side of the brain processes the signals generated by the right half of both eyes, and the right side processes the signals from the left half of both eyes. So, rather than each eye being responsible for the field of vision on the side in which they sit, they offer a combined field of vision for both sides.

In anatomy, we teach the systems of the human body using two pathways: form and function. The workings of the eyes are a great demonstration of why looking through these lenses is important. With the eyes having a symmetrical field of view, one could suffer a stroke or other traumatic injury and not completely lose their sense of sight, but rather only one side of the field of view. The way the visual sensory organs and their nerves are built and “wired” allowed the best chance of survival while we were still running the risk of falling as prey while hunting and gathering to sustain our species over a prolonged period of time. The structure and function of the eye has held true for hundreds of thousands of years.

Cited Materials:

• Right and left illustration of the brain and body: https://mayfieldclinic.com/pe-anatbrain.htm
• The eyes, optic nerve and optic chiasm: https://www.allaboutvision.com/eye-care/eye-anatomy/optic-chiasm