EPIL0GUE                                              p. 87

How the physics of light produces images for vision is relatively simple compared to grasping what happens next. There is more to the visual image than determining where the photons came from. It is also important to know what they came from.

Part of that “what” is the shape of their source. To overcome the immediate limitations of a blurred retinal image and individual receptors, the visual system has “discovered” the physical principles of spatial holistic processing and incorporated them into its neural processing. This results in a visual image with acuity that surpasses these limitations by taking into account information available from all the photons in an image.

The other Part is what their source is made of. This involves distinguishing the various wavelengths of those photons. Primates have used information processing to overcome wavelength limitations of their photon receptors. Holistic processing is used to take into account the spectral information of the entire image to evaluate the response of individual receptors.

This Glance has gone from the physics of how photons dance to the periphery of the neural responses they initiate leading to vision. A bit of photometry was added to help apply some this information to practical matters of using light to improve our lives and just maybe to explore further.

To follow this Glance further into vision, you could begin with some basics such as my “An Introduction to Neurophysiology”, International Encyclopedia of Ergonomics-2nd Ed., W. Karwowski – editor, CRC Press, 2006, p 412-424, or an updated preprint available on Research Gate. Before too long however, the complexity of the information processing becomes describable only in terms of operating principles discovered through years of perception experiments. Introductory university textbooks on perception can provide comprehensive coverage. (I used several editions of J.M. Wolfe, et al’s Sensation & Perception, Sunderland, Mass.: Sinauer Associates until retiring.) There are glimmers of how some of these principles are achieved neuro- physiologically. Therein lies a real challenge. Finally, we lack even a glimpse of how all that produces the picture in your head, its colors and shapes representing things outside your body – the greatest mystery of all.

                                                                                                   Thank you for reading,

                                                                                                   Thomy Nilsson, Professor Emeritus,

                                                                                                    University of Prince Edward Island