“We are all faced with a world of sights and sounds and other stimuli, and our survival depends on making a rapid and accurate appraisal of these. We do not see objects as such; we see shapes, surfaces, contours, and boundaries, presenting themselves in different illumination or contexts, changing perspective with their movement or ours. From this complex, shifting visual chaos, we have to extract (patterns) that allow us to infer or hypothesize objecthood.”
Vision: the action or faculty of seeing with the eye. (Oxford) Processing the “signals” sent to the brain from our eyes. (Doidge, 48)
We understand the visual system better than any other system in the brain. It is a model for how the brain works. If we understand how the visual system works in the brain, we have a very good understanding of how the other systems work. (Rose, Episode 2 Eric Kandel) We are primarily visual learners. About anywhere between one-third and one-half of the brain is devoted to pure visual processing. (MedinaBSP, 18)
Visual Acuity: the ability to see fine details. Strongest when images are focused on the “fovea” because of the high concentration of “cones” there. (Hockenbury, 92) Clarity or sharpness of vision. Visual acuity depends on the functions of “retina,” (“neurocommunication”), and the interpretative ability of the brain. Normal visual acuity is expressed as 20/20 indicating that one can see at 20 feet what should normally be seen at that distance. Visual acuity can also be influenced by “brightness,” “color,” and “contrast.” (MeSH)
Visual Imagery: using parts of your brain involved in visual perception to conjure up a pictorial memory of what you have seen with your eyes. (Blakeslee, 59) Conjuring up images in your mind’s eye. (There is) a long line of studies showing that imagery actually interferes with your real eye. You can’t actually see things as well, you can’t discriminate them as well, if you’re performing visual imagery at the same time. Suggests that (visual imagery and vision) are part of the same system. (Bergen, BSP94)
Visual Processes: we are not given an already made, preassembled visual world; we have to construct our new visual world as best we can. This construction entails analysis and synthesis at many functional levels in the brain, starting with perception of lines and angles and orientation in the “occipital cortex.” At higher levels, the elements of visual perception are of a more complex sort, appropriate for the analysis and recognition of natural scenes, objects, animal and plant forms, letters, and faces. (Sacks6, 122) You do not see with the eyes but with the brain proper. Neuronal structures in the “thalamus” and “cerebral cortex” read out the “optic nerve” signals and generate a stable, homogeneous, and compelling view of the world. (Koch, 67) Unlike “MT” and “V4,” most of the rest of the visual areas of the primate brain do not reveal their functions so cleanly when they are lesioned, imaged, or zapped. (RamachandranTTB, 61) (There is) a growing recognition that there are many ways the visual system detects motion. (Eagleman, 127)