Health

Your Brain at 40

Recent breakthroughs in neuroscience are providing answers to questions on how the brain ages and how to maintain a sharp cognitive edge.

By: Carl Zimmer
Published: December 2008/January 2009   [ Updated: Dec 22, 2008 - 12:06:56 AM ]

My computer chirps. A new message has arrived. When I click on it, my monitor fills with a picture of my brain. It is cut into 36 horizontal layers, as if someone has run my head through a deli slicer. I study the dark hollow spaces formed by the ventricles, and the furrowed outer edges of the brain, the rind known as the cerebral cortex. For the first time in my life, I can see the billions of neurons in my own brain. I can also see them in action. Each time a neuron unleashes its tiny jolt, it needs to replenish its stores of energy for the next spark. Microscopic blood vessels woven throughout the brain deliver oxygen and nutrients to neurons in need. In the picture on my computer screen, some of those clumps of busy, hungry neurons glow red or yellow. In other words, this is not just a picture of my brain. It is also a picture, of sorts, of my thoughts.

Randy Buckner, PhD, a cognitive neuroscientist at Harvard had e-mailed the picture to me. Four days earlier, I heard Buckner's voice through an intercom while I lay on a slab, dressed in hospital scrubs, with my body lodged inside a functional magnetic resonance image (fMRI) scanner. A small cage was wrapped around my face, and through the bars I could see a mirror, which reflected a computer monitor at the far end of the shaft. My head was gently held in place by a soft vise. Earplugs blocked some of the hammering and beeping of the machine. It was shooting radio waves through my head to detect the surge of blood flowing inside my brain, feeding the hungry neurons.

I went to Buckner's lab to get a glimpse of my aging brain. At 42, I can see the outward signs of time in my graying hair and my crow's-feet, and I know age-related cognitive decline starts in the forties, but it's hard for me to know what's going on inside my head. Are my neurons dying off? Is there fraying in the fibers of white matter that connect the different regions of my brain? Are my neurotransmitters failing to swim from neuron to neuron so that I lose thoughts like dropped calls on my cell phone? I do know that names sometimes take longer to come to mind and I can't work late into the night the way I used to. I wonder if the cognitive fog that comes with age is closing in and if there is anything I can do to prevent it?

Up until recently, the march of neurological time seemed beyond the control of doctors. But that's beginning to change for two reasons: Neuroscientists recently discovered, to their surprise, that neurons in the adult brain can still grow (a process known as neurogenesis) and that by thinking, learning, and acting, the brain can restructure both its anatomy and physiology (a concept called neuroplasticity). "The discovery that the brain is not a machine, as was thought, but that it is neuroplastic is the most important change in our understanding of the brain in 400 years," says Norman Doidge, MD, author of The Brain That Changes Itself and a member of the research faculty at the Columbia University Center for Psychoanalytic Training and Research. Furthermore, there is an emerging understanding of how the brain ages, and in particular, how mental sharpness has more to do with how regions of the brain are linked together in circuits than how well the individual parts work. Some observers believe we're on the cusp of a revolution in brain health similar to the fitness awakening that took place in the 1970s regarding the benefits of running and aerobics.

Neuro-enhancing treatments (drugs, diets, training programs, and workouts) are rapidly becoming mainstream. The demand for brain-stimulation products is sky-rocketing, with sales doubling from $100 million in 2005 to $225 million in 2007. In a recent survey in the journal Nature, 20 percent of scientists said they already take cognitive-boosting drugs such as Provigil (a stimulant created to treat narcolepsy) and Ritalin (a stimulant designed to treat ADHD), not to treat medical conditions, but to help them work more effectively. "It's a very promising time," says P. Murali Doraiswamy, MD, chief of the biological psychiatry division at Duke University and author of The Alzheimer's Action Plan, a memory-fitness guide for the 40-plus man, "but we need to see more clinical evidence that demonstrates the benefits and safety of these kinds of treatments on everyday brain function." The next generation of cognitive drugs may turn out to be much more powerful because Buckner and other neuroscientists are, for the first time, seeing the brain changes that cause our minds to age. "Randy Buckner's work is providing critical insights into how brain systems change with aging and disease," says Daniel Schacter, PhD, a Harvard psychologist and author of The Seven Sins of Memory: How the Mind Forgets and Remembers. Buckner's work could help lay the foundation for a new kind of treatmentsfor the brain that makes today's approach look as quaint as a 19th-century leech.

All right, Carl," says Buckner. His deep voice is rendered faint and crackling by the intercom. He speaks to me from an adjoining room. "I am going to show you a crosshair, and you're going to stare at it. Try to relax and not think of anything. Keep your head as still as possible. It will only be for six or seven minutes, but it's going to feel like a long time." Indeed. I listen to the low thunk of the scanner's cooling pumps and the alarm-clock whine of coil. The noise pushes through my earplugs like some industrial-rock soundtrack. As I stare at the crosshair, my thoughts drift like flotsam. I run through the questions I want to ask Buckner. I think about the salt marshes and strip malls that flew past my train window that morning. I think about a prospector I once met in Rwanda, holding a nugget of gold he had sieved out of a river. I think of how long six minutes can be.

It might seem like a waste of time for Buckner to take a picture of my brain while I'm not thinking of anything in particular. Shouldn't I be putting my brain to the test, trying to solve some calculus equation or recall a Shakespearean-sonnet? It turns out that wandering thoughts reveal profound clues about how we age. Buckner and other researchers have found that in our daydreams and downtime, certain parts of our brains are working very hard. This remarkable network helps gives us a sense of who we are, of our past and our future. And as we age, this network deteriorates.