The Autistic Brain: Thinking Across the Spectrum (4 page)

“Journey to the center of my brain” is what I call this experience. Seven or eight times now I have emerged from a brain-imaging device and looked at the inner workings that make me
me:
the folds and lobes and pathways that determine my thinking, my whole way of seeing the world. That first time I looked at an MRI of my brain, back in 1987, I immediately noticed that it wasn’t symmetrical. A chamber on the left side of my brain—a ventricle—was obviously longer than the corresponding one on the right. The doctors told me this asymmetry wasn’t significant and that, in fact, some asymmetry between the two halves of the brain is typical. But since then, scientists have learned how to measure this asymmetry with far greater precision than was possible in 1987, and we now know that a ventricle elongated to this extent seems to correlate with some of the symptoms that identify me as autistic. And scientists have been able to make that determination only because of extraordinary advances in neuroimaging technology and research.

Neuroimaging allows us to ask two fundamental questions about every part of the brain: What does it look like? What does it do?

Magnetic resonance imaging, or MRI, uses a powerful magnet and a short blast from a specific radio frequency to get the naturally spinning nuclei of hydrogen atoms in the body to behave in a way that the machine can detect. Structural MRI has been around since the 1970s, and as the word
structural
suggests, it provides views of the anatomical structures inside the brain. Structural MRI helps answer the What does it look like? question.

Functional MRI, which was introduced in 1991, shows the brain actually functioning in response to sensory stimuli (sight, sound, taste, touch, smell) or when a person is performing a task—problem-solving, listening to a story, pressing a button, and so on. By tracing the blood flow in the brain, fMRI presumably tracks neuron activity (because more activity requires more blood). The parts of the brain that light up while the brain responds to the stimuli or performs the assigned tasks, researchers assume, provide the answer to the What does it do? question. Over the past couple of decades, neurological research using fMRI studies has produced more than twenty thousand peer-reviewed articles. In recent years, that pace has accelerated to eight or more articles
per day.

Even so, neuroimaging can’t distinguish between cause and effect. Take one well-known example associated with autism: facial recognition. Neuroimaging studies over the decades have repeatedly indicated that the cortex of an autistic doesn’t respond to faces as animatedly as it does to objects. Does cortical activation in response to faces atrophy in autistics because of the reduced social engagement with other individuals? Or do autistics have reduced social engagement with other individuals because the connections in the cortex don’t register faces strongly? We don’t know.

Neuroimaging can’t tell us everything. (See sidebar at the end of this chapter.) But it can tell us a lot. A technology that can look at a part of a brain and address What does it look like? and What does it do? can also answer a couple of bonus questions: How does the autistic brain look different from the normal brain? and What does the autistic brain do differently than the normal brain? Already autism researchers have been able to provide many answers to those two questions—answers that have allowed us to take the behaviors that have always been the basis of an ASD diagnosis and begin to match them to the biology of the brain. And as this new understanding of autism is harnessed to more and more advanced neuroimaging technologies, many researchers think that a diagnosis based in biology is not just feasible but near at hand—maybe only five years away.

I always tell my students, “If you want to figure out animal behavior, start at the brain and work your way out.” The parts of the brain we share with other mammals evolved first—the primal emotional areas that tell us when to fight and when to flee. They’re at the base of the brain, where it connects with the spinal cord. The areas that perform the functions that make us human evolved most recently—language, long-range planning, awareness of self. They’re at the front of the brain. But it’s the overall complex relationship between the various parts of the brain that make us each who we are.

When I talk about the brain, I often use the analogy of an office building. The employees in different parts of the building have their own areas of specialization, but they work together. Some departments work closer together than others. Some departments are more active than others, depending on what the task at hand is. But at the end of the day, they come together to produce a single product: a thought, an action, a response.

At the top of the building sits the CEO, the prefrontal cortex—
prefrontal
because it resides in front of the frontal lobe, and
cortex
because it’s part of the cerebral cortex, the several layers of gray matter that make up the outer surface of the brain. The prefrontal cortex coordinates the information from the other parts of the cortex so that they can work together and perform executive functions: multitasking, strategizing, inhibiting impulses, considering multiple sources of information, consolidating several options into one solution.

Occupying the floors just below the CEO are the other sections of the cerebral cortex. Each of these sections is responsible for the part of the brain it covers. You can think of the relationship between these discrete patches of gray matter and their corresponding parts as similar to the relationship between corporate vice presidents and their respective departments.

• The frontal cortex VP is responsible for the frontal lobe—the part of the brain that handles reasoning, goals, emotions, judgment, and voluntary muscle movements.
  
• The parietal cortex VP is responsible for the parietal lobe—the part of the brain that receives and processes sensory information and manipulates numbers.
  
• The occipital cortex VP is responsible for the occipital lobe—the part of the brain that processes visual information.
  
• The temporal cortex VP is responsible for the temporal lobe—the auditory part of the brain that keeps track of time, rhythm, and language.
  

Below the VPs are the workers in these various divisions—the geeks, as I like to call them. They’re the areas of the brain that contribute to specialized functions, like math, art, music, and language.

In the basement of the building are the manual laborers. They’re the ones dealing with the life-support systems, like breathing and nervous system arousal.

Of course, all these departments and employees need to communicate with one another. So they have desktop computers, telephones, tablets, smartphones, and so on. When some folks want to talk to others face to face, they take the elevator or the stairs. All these means of access, connecting the workers in the various parts of the building in every way imaginable, are the white matter. Whereas the gray matter is the thin covering that controls discrete areas of the brain, the white matter—which makes up three-quarters of the brain—is a vast thicket of wiring that makes sure all the areas are communicating.

In the autistic brain, however, an elevator might not stop at the seventh floor. The phones in the accounting department might not work. The wireless signal in the lobby might be weak.

Before the invention of neuroimaging, researchers had to rely on postmortem examinations of the brain. Figuring out the anatomy of the brain—the answer to the What does it look like? question—was relatively straightforward: Cut it open, look at it, and label the parts. Figuring out the functions of those parts—the answer to the What does it do? question—was a lot trickier: Find someone who behaves oddly in life and then, when he or she dies, look for what’s broken in the brain.

“Broken-brain” cases continue to be useful for neurology. Tumors. Head injuries. Strokes. If something’s broken in the brain, you can really start to learn what the various parts do. The difference today, though, is that you don’t have to wait for the brain’s host to die. Neuroimaging allows us to look at the parts of the brain and see what’s broken now, while the patient is still alive.

Once when I was visiting a college campus I met a student who told me that when he tried to read, the print jiggled. I asked him if he’d had any head injuries, and he said he’d been hit by a hockey puck. I asked where exactly he’d been hit. He pointed to the back of the head. (I don’t think I was rude enough to actually feel the spot, but I can’t say for sure.) The place where he was pointing was the primary visual cortex, which is precisely where I had expected him to point, because of what neuroimaging has taught us.

In broken-brain studies, we can take a symptom, an indication that something has gone haywire, and look for the wire or region that’s damaged. Through this research, we have pinpointed the circuits in the back of the brain that regulate perception of shape, color, motion, and texture. We know which are which because when they’re busted, weird stuff happens. Knock out your motion circuit, and you might see coffee pouring in a series of still images. Knock out your color circuit, and you might find yourself living in a black-and-white world.

Autistic brains aren’t broken. My own brain isn’t broken. My circuits aren’t ripped apart. They just didn’t grow properly. But because my brain has become fairly well known for its various peculiarities, autism researchers have contacted me over the years to ask permission to put me in this scanner or that. I’m usually happy to oblige. As a result of these studies, I’ve learned a lot about the inner workings of my own brain.

Thanks to a scan
at the University of California, San Diego, School of Medicine’s Autism Center of Excellence, I know that my cerebellum is 20 percent smaller than the norm. The cerebellum helps control motor coordination, so this abnormality probably explains why my sense of balance is lousy.

In 2006 I participated in a study at the Brain Imaging Research Center in Pittsburgh and underwent imaging with a functional MRI scanner and a version of MRI technology called diffusion tensor imaging, or DTI. While fMRI records regions in the brain that light up, DTI measures the movement of water molecules through the white-matter tracts—the interoffice communications among the regions.

• The fMRI portion of the study measured the activation in my ventral (or lower) visual cortex when I looked at drawings of faces and drawings of objects and buildings. A control subject and I responded similarly to the drawings of objects and buildings, but my brain showed a lot less activation in response to faces than hers did.
  
• The DTI scan examined the white-fiber tracts between various regions in my brain. The imaging indicated that I am overconnected, meaning that my inferior fronto-occipital fasciculus (IFOF) and inferior longitudinal fasciculus (ILF)—two white-fiber tracts that snake through the brain—have way more connections than usual. When I got the results of that study, I realized at once that they backed up something I’d been saying for a long time—that I must have an Internet trunk line, a direct line—into the visual cortex to explain my visual memory. I had thought I was being metaphorical, but I realized at that point that this description was a close approximation of what was actually going on inside my head. I went looking for broken-brain studies to see what else I could learn about this trunk line, and I found one
  that involved a forty-seven-year-old woman with visual memory disturbance. A DTI scan of her brain revealed that she had a partial disconnection in her ILF. The researchers concluded that the ILF must be “highly involved” in visual memory.
  Boy,
  I remember thinking,
  break this circuit and I’m going to be completely messed up.
  

In 2010 I underwent a series of MRI scans at the University of Utah. One finding was particularly gratifying. Remember that when I pointed out the size difference in my ventricles to the researchers after my first MRI, back in 1987, they told me that some asymmetry in the brain was to be expected? Well, the University of Utah study showed that my left ventricle is 57 percent longer than my right. That’s huge. In the control subjects, the difference between left and right was only 15 percent.

My left ventricle is so long that it extends into my parietal cortex. And the parietal cortex is known to be associated with working memory. The disturbance to my parietal cortex could explain why I have trouble performing tasks that require me to follow several instructions in short order. The parietal cortex also seems to be associated with math skills—which might explain my problems with algebra.

Back in 1987, neuroimaging technology wasn’t capable of measuring the anatomical structures within the brain with great precision. But if those researchers back then knew that one ventricle in my brain was 7,093 millimeters long while the other was 3,868 millimeters long, I guarantee it would have given them pause.