“Normal” Disabilities

The brain shapes our inner reality, and in my previous post I discussed the way neurological damage can distort our reality-sense. I offer other examples in Your Living Mind. But those of us who are “normal” also experience the world in ways that are irrational. Scientists are discovering more and more ways in which normal humans suffer from perceptual disabilities. Perception does not just duplicate the outside world, as if we were photocopy machines.

One example of a normal disability is inattentional blindness. It may seem as if we would surely be aware of anything we’re looking at directly. But if people are paying attention to one thing they may not see something else, even if they are gazing straight at it. In one study subjects were asked to stare at a fixed point, but they had to report whenever an X appeared a few inches away from the point they were gazing at. So they were looking at one point but staying alert for randomly appearing Xs nearby. Partway through this task, without warning, some letter or shape would appear at the fixation point, right where they were looking. Many did not see what unexpectedly appeared, even though they were looking right at it!

Interestingly, some kinds of items were usually noticed. “The two most reliable of this small group of attention-capturing stimuli are one’s own name and the iconic representation of a happy face” (Arien Mack, “Is the Visual World a Grand Illusion? A Response,” Journal of Consciousness Studies, May/June, 2002, p. 108). But if even one vowel in the name is incorrect, we are unlikely to detect it, “suggesting that it is the meaning of the stimulus that captures attention and not some lower-level stimulus attribute” (p. 109). After information about what we are staring at travels up the optic nerve into our brains, cerebral sentries note the significance of this perceptual data, and decide whether to let it become conscious.

Here’s a frightening example of inattentional blindness. Pilots in training use a simulator to practice flying while they’re safely on the ground, watching a screen that duplicates what they would see out the windshield of an aircraft. At one point NASA was testing a display that projects navigational information onto the windshield, as if the information were floating out in front of the airplane. Sometimes pilots were “using a display, commenting on how nice it was, while landing their aircraft right on top of another aircraft taxiing onto their runway in plain view” (Daniel Levin, “Change Blindness Blindness As Visual Metacognition,” Journal of Consciousness Studies, May/June, 2002, p. 127). Their attention was on the new display, so they overlooked a huge moving obstacle right in front of them!

Roger Christan Schriner

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Change the Brain, Change “Reality”

The brain creates our core sense of reality, and we can learn a lot about that by noticing what happens when it is damaged by aging, accident, or illness. For example, sometimes an injury or a stroke alters neural structures that help constitute our experience of reality, including concepts of front and back, left and right, clockwise and counterclockwise. Then it’s as if one of the stage sets for our personal Truman Show has suddenly collapsed. (See “Your own little Truman Show,” December 8, 2014.)

In rare cases after a stroke, a patient’s visual experiences become a mirror image of normal experiences. As a result, books can be read only if they’re held up to a mirror. Such individuals write the mirror image of their signature and want to drive on the left-hand side of the road! That’s a fairly basic reality shift.

Or consider hemineglect, in which people ignore half of their world as if it isn’t there (usually the left half). When asked to copy a drawing of a flower they only draw the right side. They still realize that every object has two sides, but the brain modules which structure their experience of the world in terms of left and right have been damaged.

Neurologist Oliver Sacks tells of a stroke patient who would only eat the right half of a plateful of food. She could, of course, have turned the plate around after eating half of her meal. Then the neglected left half would have become the effortlessly-noticed right half. But since it was so hard to focus on “leftness,” she would physically move, turning around in a circle to the right. Looking at the plate again she would see the remaining food – or at least the right side of what was “left” over. She would do this several times, consuming one half after another until only crumbs remained.

This patient was highly intelligent and could even joke about the conceptual predicament of hemineglect. “It may look funny, but under the circumstances what else can I do?” When she tries to rotate the plate rather than rotating herself, “it is oddly difficult, it does not come naturally, whereas whizzing round in her chair does, because her looking, her attention, her spontaneous movements and impulses, are all now exclusively and instinctively to the right.” “‘It’s absurd,’ she says. ‘I feel like Zeno’s arrows – I never get there’” (The Man Who Mistook His Wife for a Hat, pp. 77-78).

In mentioning Zeno, she was referring to a Greek philosopher who asked how an arrow could ever arrive at its target. After all, before the arrow lands it has to go halfway, before going halfway it has to go 1/4 the distance, before that 1/8, and so on ad infinitum. Thus the stroke patient consumed half of her food, 1/4 more, and so on. So even though she knew she was succumbing to an illusion, her compelling inner sense of the way things are overwhelmed her intellectual insight.

So when the brain changes, reality changes – or seems to.

Roger Christan Schriner

More on the Elusive NCC

Earlier this month I discussed the difficulty of finding the NCC, the neural correlates of consciousness. It is extremely hard to know which aspects of a brain’s activity constitute (or generate) conscious processes and which are the unconscious accompaniments of our conscious experiences. Those who are interested in this problem may want to read “Why the Neural Correlates of Consciousness Cannot be Found,” by Bernard Molyneux (Journal of Consciousness Studies, No. 9–10, 2010).

Molyneux asks whether we can discover “the perfect correlate of consciousness – the neural events that occur, in both normal and abnormal circumstances, when and only when consciousness is present. However, consciousness correlates not only with the NCC but also with its causes, its consequences and with other associated states. Hence, to determine the true NCC, we need to drive these states apart to see which one consciousness tracks, by holding one constant while obliterating its usual correlates”(p. 169). I don’t think we need to “obliterate” any brain states to study consciousness, but I agree with Molyneux that it is very hard “to distinguish the ‘one true’ NCC from closely associated phenomena” (p. 169).

I’m not ready to give up on finding the NCC. So many times in the history of science some pundit has declared that we will never be able to discover such-and-such, and 50 years later we do. And Molyneux does seem to admit that there’s a ray of hope: “… the problem demands a greater appreciation of when a seeming dispute between NCC researchers cannot be empirically settled, and calls for a more perfect philosophical explication of what exactly it is that we can hope to find when we set out to look for the (rather than a) neural correlate of consciousness” (p. 169). Very true, and this is an example of the practical relevance of philosophy.

Roger Christan Schriner

Your own little Truman Show

“Reality … what a concept!” This title of a CD by the late Robin Williams suggests that what we think of as reality is our own conceptualization, and I believe that the brain assembles the only reality we are able to know. Every message we receive through our ears, eyes, nose, tongue, and skin is elaborately processed before we become aware of it. There is no way to experience life as raw data. Our brains feed us French toast rather than kernels of wheat topped with unshelled eggs. In that sense the direct realist’s claim that nothing stands between us and the objects we perceive is rather misleading.

Perceptions are processed in ways that help us cope. For example, visual information is cleaned up and enhanced after it arrives in the brain. Suppose we are looking at an object that is equally bright all over its surface, according to exact measurements of brightness levels. To us its brightness will not seem uniform; it will seem brighter at the edges and corners than in the middle. By artificially brightening edges and corners the brain exaggerates boundaries, so that it’s easier to tell one thing from another. How convenient to see a universe of specific objects instead of a swirl of bewildering stimuli.

Changes are also exaggerated, making it easier to notice the movements of an animal. And when we watch a moving object, we experience it as being slightly ahead of its actual location. This helps a baseball player hit a fastball that’s ripping along at nearly 100 mph – and helps pitchers fool batters by throwing them a curve. Cavanagh reports that “when targets are moving, they are seen ahead of their actual retinal location because they are seen at their predicted next location” (“Perceived Location: A New Measure of Attention,” Conference Handbook, Association for the Scientific Study of Consciousness, July, 2013, p. 15).

There are blood vessels in the eye, right in front of the retina, and it would be confusing to peek out at the world through a grillwork of capillaries. So how does the brain solve this problem? Very simply. Anything that stays perfectly still in relation to the eyeball is invisible. Whenever the eyeball moves, the blood vessels move with it, so the blood vessels aren’t seen except under unusual conditions.

As you look at an object, a river of information flows up the 1.2 million fibers of your optic nerve into your brain. Once it arrives there, an early stage of processing establishes edges. One neural system graphs the horizontal lines and another attends to straight-up-and-down vertical lines. Others monitor an object’s shape, color, location, or name.

Sometimes people who have had a small stroke will lose one of these subsystems, but the others will remain intact. For instance, they may be able to name an object they are looking at and accurately describe it – but they have no idea where the object is located in relation to other objects! Their visual experience has changed in a way that is virtually impossible for normal people to imagine. They’ve lost their inner map of object location.

In a film called The Truman Show, the main character starts to suspect that what he thinks is real is just a made-up story. Eventually he discovers that the world he had known since birth was actually an enormous stage set. And we are all the stars of our own Truman Show. The brain manufactures our world and fabricates the way we feel about it. Presumably a lot of this brain-made story is reasonably accurate, but some of it is pure fantasy.

I like to picture my brain as a huge Tinkertoy sculpture, with billions of interconnected spools and dowels. Activate the connections of these units in one way and you feel like dancing. Switch around their activation patterns and you sink into existential angst. It seems as if “reality” has changed, but it’s all just patterns in our heads. If you can change the pattern, you can change yourself.

Roger Christan Schriner

The Complexity Trap

It’s hard to prove that the conscious mind is located in the brain. One problem is that both mind and brain are incredibly complicated, and it’s hard to map one sort of complexity onto the other. Popular media sometimes imply that science has accomplished this feat, but this isn’t so.

Suppose we ask subjects to visualize a square, then a circle, then a square again, while their brains are scanned for signs of neural activity. And suppose this experiment enables us to print out colorful pictures showing that brain regions 1-2-3 are especially active while subjects visualize squares, and regions 4-5-6 are especially active while they’re imagining circles. Does this show that the experience of fantasizing squareness is located in 1-2-3 and fantasizing circularity is located in 4-5-6?

Not at all. It’s a start, but barely that, and I’ll just mention two of the many difficulties.

1. How much of a lit-up region is the experience of the item, and how much of it is a motley assortment of non-experiential accompaniments? Visualizing a square may call up all sorts of associations with square items and with the word “square” – square meal, square deal, square mile, and “you’re so square.” Perhaps activity in linguistic regions involves verbal associations only, and is never part of the mental image itself. Perhaps. But we don’t know for sure.

2. It’s also hard to know which aspects of a brain’s activity are conscious processes and which are the unconscious accompaniments. A great deal of the brain’s visual processing, for example, never reaches the level of awareness.

Someday we may be able to detect precisely which neural activities constitute, say, a visual experience of seeing a single cherry blossom, but this will certainly not be easy. Compare the task of identifying precisely which electromagnetic waves in the signal from a TV satellite constitute an image of the seams of a football being passed during the last five seconds of the 2015 Superbowl. We assume that this part of the video signal is a physical event, and our inability to precisely specify it does not make us philosophically puzzled. But the difficulty of knowing just which brain activities constitute a particular experience may make us wonder whether this experience could be in the brain. Complexity confuses us, so beware of the complexity trap.

I recall a lecture in which the speaker announced that he was going to display his model of the neural correlates of consciousness, or NCC. The NCC is whatever cluster of neural activities correlates with conscious experiences, and finding such a correlation would be a big step toward showing that experiences are constituted by neural processes. He then showed us a diagram with about 50 arrows going in all sorts of directions.

He was joking, of course, because we have no idea how to sketch the NCC. We need to remind ourselves that the brain is much more complex than we can comprehend, and that we are in this convoluted mish-mash.

Roger Christan Schriner