Monday, December 10, 2012

From Eye to Brain

Human sight is an ultimate production of the brain. As I look across the room from my computer keypad there would be no cognizance of the scene without my brain’s interpreting ability. My brain provides conscious awareness of the reality of the scene. Without a functioning mind sight does not occur. Light is a physical phenomenon present whether there is an observer or not, but sight is a subjective phenomenon based on external physical light stimuli. We need a human being to enjoy the subjective experience of human sight.

The transmission of information from the retina via cell extensions called axons through the optic nerve to the brain is one of the most fascinating processes related to the sight sequence. Each optic nerve contains over one million nerve fibers. We may understand the function of optic nerves by comparing how digital photographs are transmitted through a USB cable from a camera to computer storage files. Our digitally literate young people easily grasp this example of modern digital communication. Their personal photographs are transmitted as millions of tiny electrical impulses. The impulses carry the photograph to the computer, they explain. Older citizens might have a bit more trouble understanding how the process works.

These electrical impulses are called “action potentials,” tiny, repeated changes in voltage. Each change is like a light switch being turned on or off. There is no “in between.” In our eyes, 100 million rod cells and four million cone cells sense photons of light. Nerve cell endings then transmit millions of “all-or-nothing” electrical messages to the brain. Each of two optic nerves, one from each eye, contains about one million neural conduits. Our brain receives many millions of on or off electrical messages through the optic nerve each moment from the retina where the external image is projected and focused. The process works with divine simplicity.

The more than 100 million tiny rod and cone cells perceive varied light stimuli and send millions of different electrical messages from each data point projected on the retina. Millions of data points produce a plentiful trove of digital information. In a computer analog, the computer is able to convert received digital information from multiple data points into a high resolution image. The high resolution photographic image will possess no meaning for us until we observe and interpret it as though we were observing the image in real life.

The simplicity of digital messaging, either in technological applications or in the body’s own central nervous system, is belied by the presence of a multitude of physical constants and physical laws set in place by the Creator. Digital signaling, however, is governed by simple “ons” or “offs.” Scientists have figured out a way to use these on or off signals in hundreds of modern applications unheard of several generations ago.

Digitally literate young people have no have trouble mastering the underlying principle of digital technology. Neither do they stumble at the operational logic needed for mastering their ubiquitous remote units and computer driven devices. Our legitimate apprehension for modern users of technology, young or old, is the loss of wonder, amazement, and reverent awe of the Creator. He is the author of physical constants and laws of nature operating in our bodies and in our technology. God has enabled seven billion souls to benefit from application of physical constants and laws authored in his divine mind.

Our prayer is that we would give glory to God for these wonders. He designed the simple beauty of our body’s nervous system, including the concluding steps of the marvelous sequence of sight. Psalm 139:13-14 (NLT) declares: “You made all the delicate, inner parts of my body and knit me together in my mother’s womb. Thank you for making me so wonderfully complex! Your workmanship is marvelous—and how well I know it.”