Our Western diet is famously bad for the circulatory system, but for a long time, people thought the damage stopped there. Then around 10 years ago, Terry Davidson, a behavioral neuroscientist, wondered whether our modern eating habits might also affect our brains.
To test it out, he fed lab rats a diet high in saturated fats and sugars. He found that the animals had problems learning various memory tasks for which they'd get rewards. Their difficulties were probably linked to changes in the way blood reaches a portion of the brain called the hippocampus. Researchers have detected similar impairments in people who consume lots of saturated fats, says Davidson, now director of the Center for Behavioral Neuroscience at American University in Washington.
"There was no reason to think the brain would be protected, and it doesn't seem that it is," he says.
The Western diet is just one among many hallmarks of modern life that may influence brain biology. From Big Macs to digital screens to the air pollution spewed from automobiles, researchers are exploring how all kinds of 21st century conveniences are changing the way the brain works — for better and for worse.
In one preliminary brain-imaging study of 24 adults ages 55 to 76, those accustomed to using online search engines had twofold greater overall brain activity while searching than did digital newbies. The finding suggests computer use had strengthened their brain circuitry.
"We think brains are getting more efficient," Small says. "It's like you're building mental muscle."
Small believes these Internet mental workouts could be harnessed to preserve memory as people age. But there's a downside: Research indicates that younger people who have grown up as digital natives have strong technology skills but lag on social skills and emotional intelligence.
"How we use these devices has a big effect on our lives," Small says.
Internet-induced multitasking poses a particular threat, argues neuroscientist Daniel Levitin of the Minerva Schools, a university based in San Francisco. That's because focus is regularly diverted, and attention is divided among more tasks than the brain can manage at once.
"There's a neurobiological cost," he says. "You burn glucose, the fuel of the brain, every time you switch tasks."
What's more, Levitin adds, researchers have shown that cognitive overload can trigger release of the stress hormone cortisol — which, in turn, tends to suppress the brain's ability to engage in careful, systematic thought.
"Our brains get scrambled, we're not able to think clearly, and we lose productivity," he says.
Environmental pollutants — such as auto emissions, as well as pesticide exposure among people in farming communities — could also be affecting brain health, some studies suggest. But researchers' understanding of how they do so, and how significant the effects, is incomplete, says Dr. Beate Ritz, an epidemiologist at UCLA. She adds that as exposure builds up over decades, these pollutants might contribute to cognitive decline as more and more of us live longer.
"We're just beginning to understand it," she says.