Coinciding with the release of her new book this week, today’s Wall Street Journal Review section features an essay by Sue Barry that will attract the eyes of anyone who has a basic interest in, or curiosity about vision. In it she writes: “For most of us, vision feels so seamless because it results from a combination of ‘bottom-up’ and ‘top-down’ processing. ‘Bottom-up’ implies constructing the visual world from the smallest pieces of visual information. These details are, in large part, handled by neurons in lower areas of the visual cortex. But we cannot think of these neurons as responding only to the ‘bottom-up’ stimuli that our eyes provide. Their activity is modified by input coming from their neighbors as well as from other regions of the brain.
Prior experience, past associations and our level of attention all influence the firing of lower-area neurons, a process that depends on feedback from higher visual areas and is therefore called ‘top-down.’ Since we all have different experiences, needs and desires, ‘top-down’ influences differ from person to person. We all see the world through our own perceptual lens.”
Sue tantalizingly relates a key element of correspondence from Liam McCoy, one of the two protagonists of this brilliant book on sensory restoration: “Up close,” Liam wrote, “things are more like objects than visual chaos, but there is a definite difference when I see something further away. Those objects have no meaning, and I struggle to tell if a bar of color is the front of a truck or side of a bus or roof of a building. If people even stand slightly further away and talk to me or say hi from down the hall, it has a very different feeling, and it doesn’t seem as real.”
Readers’ comments at the end of online essays can be interesting, as is the case with several of the Wall Street Journal commenters here. One writes: “I’m surprised that no mention is made of Oliver Sacks’ piece (in An Anthropologist on Mars, 1995) about Virgil, a man who regained his sight after almost a lifetime of blindness. In the piece Sacks describes how fragmented Virgil’s visual world was once he could ‘see’.” There is irony in the writer apparently not knowing how much Sue has been influenced by Oliver Sacks, and about their collaboration.
Another writes: “Read a memoir called “Crashing Through” years ago by Michael May who was blinded at age 3 and tells about his remarkable life without vision and getting surgery to regain eyesight as an adult. As a happily married father and successful professional he talks about the struggle he went through to decide to have surgery, wondering why he needed to see when his life was great as it was.” Actually the book to which the commenter is referring was authored by Robert Kurson, but the point regarding Michael May is pertinent, and about which I have commented elsewhere.
But the best comment thus far comes from Mark Kofman, who notes: “This is a great article. Writing software from scratch is indeed a breeze, but going back and modifying it to perform additional processing to incorporate additional functionality is much more complex. Not only does the programmer have to contend with the framework for new functionality, but he also has to constantly reconcile it with the assumptions that have gone into the original design. Same for writing a novel and then adding to and modifying elements of the plot to credibly portray a different story arc. Same for modifying architectural blueprints. Modifying an existing structure is always more difficult than designing one from scratch, and the only reason it’s even done is because redesign from scratch takes longer (despite being less complex). For people like Liam redesign from scratch is not an option and integrating a new sense into existing neural framework requires immense effort. Ditto for older people using new technologies or parting with obsolete political ideologies.”
Keep an eye out for the next issue of VDR, due online at the end of the month. It will contain a book review of Coming to Our Senses written by our colleague, Dr. Paul Harris.