PANTHEON, JANUARY 2016Walter had been acting strangely. When friends or family visited, he ignored them unless they spoke directly to him. Until they uttered a sound, it was as if they weren’t even there. While walking around his living room, Walter stepped right into his coffee table, then into the wall. He missed widely when reaching for a cup of coffee and knocked over a vase instead. At age fifty-five, Walter was having problems with his vision, yet, inexplicably, he said there was nothing wrong with his eyesight. But why, Walter’s family wondered, would he deny it? Why wouldn’t he seek out help? Confused, they pressed him to go see a neurologist. Walter reluctantly agreed. When he arrived, Walter had the following exchange with his doctor:
NEUROLOGIST: How are you?
NEUROLOGIST: Anything wrong with you?
WALTER: No. Everything’s perfect.
NEUROLOGIST: Anything wrong with your vision?
WALTER: No. Works fine.
NEUROLOGIST (showing a pen): Then can you tell me what this is?
WALTER: Doc, it’s so dark here; nobody can see anything.
With daylight streaming in through the window, the room was plenty bright. Nevertheless, the doctor humored him.
NEUROLOGIST: I put the light on. Can you now see what I have here?
WALTER: Look, I don’t want to play games with you.
NEUROLOGIST: Fair enough. But can you describe how I look?
WALTER: Sure. You are a small, fat chap.
The doctor, who was actually tall and thin, understood that Walter wasn’t simply denying that he was blind. He actually didn’t realize it. Was he delirious? Was it early Alzheimer’s? Perhaps he needed to speak with a psychiatrist.
The neurologist could infer that there was a connection between Walter’s loss of sight and his delusion that everything was fine. Behavioral tests, however, would not be able to identify that connection. He would have to peer inside Walter’s brain. A CT scan of his head revealed that Walter had suffered a massive stroke, causing damage to both sides of his occipital lobe, which processes vision. That explained the blindness. But the CT showed something else: damage to the left parietal lobe. Among its many functions, the parietal lobe helps interpret sensory signals, especially visual ones. It compiles the basic visual information sent from the occipital lobe and integrates it to help construct a streamlined picture of the world. The parietal lobe is involved in monitoring how the visual system is working. But what if that monitoring function were impaired?
Walter was diagnosed with Anton’s syndrome, a rare disorder in which blind people don’t realize they are blind. Patients with Anton’s syndrome tend to make excuses for their perceptual mistakes, such as “I’m not wearing my glasses” or “There’s a lot of glare from the sun.” As one theory goes, this happens because there is a disconnect between the visual system and the brain regions that monitor it. As a result, the brain never gets the message that there’s a problem with vision. That’s why Walter didn’t realize he was blind.
But this story goes deeper still. Not only did Walter fail to admit his blindness, but he came up with an alternative explanation for his symptoms (“It’s so dark here”). Walter’s brain was faced with a confusing situation. On the one hand, the brain was having trouble perceiving the world. On the other hand, because of the stroke, the brain didn’t know that the visual system had been destroyed. What could explain a loss of sight in a person with an intact visual system? It must be dark in here. Faced with contradicting pieces of information, the brain came up with a story to reconcile them. And it was a pretty good one. You might even say that given the circumstances it was perfectly logical.
Deep within our subconscious, there is a system that quietly processes everything we see, hear, feel, and remember. Our brains are constantly bombarded by innumerable sensations streaming in as we interact with our surroundings. Like a movie editor who collects and organizes all the footage and audio to create meaningful stories, the underlying logical system in the brain assembles all of our thoughts and perceptions into a sensible narrative, a narrative that becomes our life experience and sense of self. This book is about that underlying logic and how it creates our conscious experience, whether in those suffering from the weirdest neurological illnesses or during our simplest day-to-day feelings and decisions.
Our objective will be similar to that of other books in the popular science and psychology domain: Can we discover the underlying reasons for the way we think and act? However, we will take a different approach. Many books you might have encountered on the brain rely on behavioral research that, while enlightening in its own right, often doesn’t look inside the brain to tell us where that behavior comes from. Suppose I give you a machine hidden inside a black box and ask you to figure out how it works. The catch, however, is that I don’t let you see what’s inside. All the gears and pulleys and levers are concealed within the dark encasing. How would you assess what the machine does? Without the ability to examine the underlying mechanics, all you can do is try using the machine in various ways and look for patterns. From there, you can infer how the machine works, but there would still be an element of conjecture. This is a real-world problem in fields like engineering and software development. Consider a software engineer who tries to decipher how a program works without having access to the underlying code. In what is called black box testing, the software designer enters a variety of inputs (such as pushing a button) and records the outputs (seeing what happens) to make educated guesses about how the system works, all without any knowledge of its actual internal structure or mechanics.
In this book, we will explore questions about human consciousness by cracking open the black box of the brain and peering at its inner workings. In the process, we’ll discover that underlying many of the most mysterious phenomena of human experience, and even the simplest day-to-day decisions, there are distinct neurological circuits, uniting seemingly disconnected facets of our life experience with a single explanation.
Excerpted from NeuroLogic Eliezer J. Sternberg. Published in 2016 by Pantheon. © Eliezer J. Sternberg, 2015.