|By: Jim Virkler; ©2012|
Do you get the picture? This familiar idiom asks if the listener understands a situation clearly. In terms of understanding literal visual pictures, that is, understanding the meaning of the information our eyes provide, we sometimes come up short teaching the role of mental processes involved with seeing. Stated another way, even in early grades students may begin to understand the connections between body senses and the mind’s ability to make sense of messages our body receives from the outside world. Sensory information means nothing without a sentient, conscious, operating mind. I recall repeating to my classes that our eyes merely receive information via light energy: “But it is our brain which figures it all out. The brain really does the seeing.”
Science instructors teaching light and sight units may rely too much on analogies between our eyes and a camera. For example, the camera has a lens to capture light from billions of data points--light producing points--in our environment. Billions of rays of light from multiple light data points in our surrounding world enter the camera through a tiny opening. Based on our students’ unspectacular discovery that light rays travel through the medium surrounding us in straight lines, simple diagrams of the camera phenomenon may be drawn. Light rays coming from the top of our field of vision enter the camera and fall on the bottom of the image sensor. Meanwhile, light rays from the bottom of our field of vision enter the camera’s tiny opening and fall on the top of the image sensor. Students discover image inversion. Holding a magnifying glass at arm’s length illustrates the inversion phenomenon.
Students discover that a tiny, extremely finely-detailed, focused picture of our sight field falls on our retina inverted and reversed. The student may ask, “Is this how we see?” No, this is just the beginning of our discovery! The remaining wonders revolve around nerve impulses, more technically termed called action potentials. These nerve impulses, tiny electrical charges, are integrated from information received from over 100 million photoreceptor cells in the retina on which the tiny image is focused. Integration consists of processing the information and transmitting it through approximately one million optic nerve fibers to the part of the brain called the visual cortex, a small area in the back of the brain. Some integration takes place in the retina. The main processing of information, however, takes place in the visual cortex.
Biology (7th edition), an Advanced Placement, 1231 page text authored by Neil A. Campbell and Jane B. Reece, is one of many wonderful resources for advanced students of biology. Campbell and Reece summarize their section on “Processing Visual Information” as follows:
Point-by-point information in the visual field is projected along neurons onto the visual cortex. How does the cortex convert a complex set of action potentials representing two-dimensional images focused on our retinas into three-dimensional perceptions of our surroundings? Researchers estimate that at least 30% of the cerebral cortex—hundreds of millions of interneurons in perhaps dozens of integrating centers—take part in formulating what we actually “see.” Determining how these centers integrate such components of our vision as color, motion, shape, and detail is the goal of an exciting, fast-moving research effort.
Our concern for today’s population revolves around their primary focus on the operational functions of camera technology, to name one example. Seldom do they discuss how their technological marvels actually work or what historic discoveries led to our present level of achievement. Instead, their conversations center on how such innovative technology enriches their entertainment experience. They master operational skills easily, but their fascination for how their technological marvels actually work may take a back seat.
“Getting the picture” of everyday human vision is far more gripping. Do we comprehend the wonder of our ability to immediately recognize and process the events portrayed in our visual field? Do we consider how our memory of past events instantly integrates with events observed in the present? Campbell and Reece, authors of Biology, observe, “Each neuron may communicate with thousands of other neurons in complex information-processing circuits that make the most powerful electronic computers look primitive.”
Samuel F. B. Morse’s first telegraph message was transmitted on May 24, 1844 between Washington and Baltimore. The message contained a phrase from Numbers 23:23: “What hath God wrought?” If Morse’s simple, technologically primitive electronic message deserved an epiphany giving credit to God, how much more may we apply the exultation to the wonders of “neurons in complex information-processing circuits” in the human body “that make the most powerful electronic computers look primitive.” The process of human sight is an occasion to give glory to God.