The Joy of Sacks -- Recruiting Resources

While trolling the library the other day for a stack of new trashy mystery novels (my relaxation of choice these days), I was delighted to find a new case study collection by Oliver Sacks, The Mind’s Eye (Borzoi, 2010). Sacks is a neurologist who first became famous with the publication of a collection similar to this, The Man Who Mistook his Wife for a Hat (Touchstone, 1998). If you have any interest at all in how the mind works, I strongly recommend Sack’s work. These case studies tell stories of individuals who suffer some brain injury and as a result lose a piece of what they usually do automatically. These dissociations of functions we normally see as unitary gives real insight the functioning of the brain. The title case study of the 1998 book is about a music professor who lost the ability to pull together bits of visual data into recognized objects. He really did, at one time, reach over to grab his wife’s head because the curve of her scalp matched the curve of his hat.

What I find particularly meaningful – and hopeful – about Sacks’ case studies is that he often picks ones where the people who have suffered a brain injury and a resulting loss nonetheless do not fall into despair, as many must, but find a way to go forward with their lives. He tells of an athletic young woman in TMWMHWFAH who lost her ability to interpret the signals from her muscles telling her about the orientation of her body and limbs (her proprioception) and almost became effectively paralyzed as a result – she would flail around knocking into things. But she worked to learn to replace her muscular perceptions by visual ones and regained much of her ability to function normally. A painter (in TMW…) lost his color vision and, instead of giving up painting, developed a new (and, it turns out, more popular) style. A novelist (in ME) had a stroke and lost his ability to read – but not to write (alexia sine agraphia)! He could write but couldn’t read what he had written to revise or build coherency. He learned to dictate and have people read to him and he has continued to maintain his output (of mystery novels).

I know that these are selected stories and that many people’s illnesses and injuries are too severe to give them a path back to a life of satisfaction and joy, but as I get older and the probability of something bad happening increases, I get satisfaction in knowing that at least some people manage to get over even severe bumps in the road.

But I digress. (Hey! I’m an academic! That’s what I do. Get over it.) The point of this screed is not for me to get maudlin about aging; it’s to see what points these stories make about how the brain works. I’ve got two for now.

The story of the novelist makes me appreciate the role of external objects and symbology as components of our everyday cognition. (cf. some parts of activity theory)  My best example of this is building a talk in PowerPoint. I know how to do lots of things with PowerPoint – but it’s me and PowerPoint that know it together; I don’t know it by myself.  Occasionally someone will ask me how to do something in PPT. I might know, but not be able to tell them. What I know is which chain of items to choose from a series of menus when they are presented to me – but I don’t have the menus themselves stored in memory. When I am deriving something in physics or math that requires far more steps than the 7 ± 2 that fits easily in my working memory, it looks like I have much more in play since I write my equations down and by scanning up and down the page, I can quickly swap in and out what I need without having to reconstruct those that I can’t keep active. Writing a novel (or an academic paper) certainly must be dramatically simplified by our ability to have written stuff down and quickly look back at it.

But the case study in The Mind’s Eye that really excited my and is responsible for my pulling out the computer on a Saturday night is “Stereo Sue”. In this, Sacks tells of a woman born with strabismus (cross eyes). Despite a number of operations when she was a child, she never achieved true stereoscopic vision. Now lots of animals get along without stereoscopic vision. In fact most prey animals such as antelopes and deer (also horses) have eyes that are on the side of their head so they can scan closer to a full circle more quickly. Presumably they have much more awareness of what’s to the side and behind them, but we seem to be descended from tree-living animals that had much more need of depth perception to negotiate a complex 3-D environment.

Now Sue was able to get along just fine using the other parts of her vision that allows us to place ourselves in space, particularly motional parallax – how things appear to change when you move. She could drive and even play softball. But in her 40’s she began to develop problems with her vision. She found a careful and flexibly thinking doctor who discovered that not only had she been cross-eyed, but the vertical alignment of her eyes was off. By adding prisms to her glasses, the doctor was able to correct this. And, with a series of exercises, Sue was able to initiate stereoscopic vision.

I wish I could repeat the whole story here, but this is too long and I want to (eventually) make a point. Go read it for yourself. I actually have two more points to make, one about the practice of science, one about the brain.

First, for decades, Sue’s doctors told her that because she had missed the “critical period” as an infant, her brain would never be able to learn to interpret the data from her two eyes stereoscopically. Of course that’s the result that Hubel & Wiesel found with kittens (and won the Nobel prize for). It’s a great result, but it does not obviously carry over to other species (ferrets, for example) and the human brain seems way more plastic – at least potentially – than we often assume. There are stabilities, but we may be making a serious error when we ignore or under-appreciate the possibility of dynamic reorganization.

My second point about the brain is this. After Sue had pretty fully developed her stereoscopic vision, Sacks tested her with an interesting example. This was text presented in a stereoscopic viewer – strings of unrelated words. When viewed monocularly, it looked just like text on a page – flat. But viewed stereoscopically, it became obvious that the words were on different levels – as if they were printed on stacked panes of glass.

When Sue first looked at this she saw the text as flat. When Sacks pointed out the 3-D aspect, she said, “Oh, now I see” and was able to see it just fine. Sacks says

“Given enough time, Sue might have been able to see all seven levels on her own, but such “top-down” factors – knowing or having and idea of what one should see – are crucial in many aspects of perception.”

Later he says

“If a stereo photograph is flashed on a screen for as little as twenty milliseconds, a person with normal stereoscopy can perceive some stereo depth straightaway.  But what one sees in a flash is not the full depth; the perception of this requires several seconds, even minutes, in which the picture seems to deepen as one continues to gaze as it – it is as if the stereo system takes a certain time to warm up…. The underlying cause for this is unknown, though it has been suggested that it entails the recruitment of additional binocular cells in the visual cortex.”

This just strikes me as so similar to what I see with my students operating at a much higher level of brain activity and complexity. I find it delightful to see framing and the need to recruit other resources before something clicks into making sense occurring at the direct perceptual level.