USE IT OR LOSE IT

WE PUT OUR BRAINS ON AUTOPILOT WHEN WE TURN ON THE GPS, AND THAT COULD BE SHRINKING OUR GREY MATTER

Afew years ago on a visit to the high desert of northern New Mexico I punched the name of a local hot spring into my phone’s navigation app and set off in my car, following the directions down a twisty dirt track that ended 10 metres from the edge of a cliff. Some 30 metres below was the Rio Grande and, I assumed, the hot spring. The directions would have been perfect if cars could fly.

Stories of being led astray by satellite navigation systems such as GPS are increasingly common as digital devices become ubiquitous in our daily lives. Some tales are simply ridiculous, others have ended in death.

While many of the reports we hear about tragedy on the roads involving technology have to do with drivers distracted by using their devices while at the wheel, research has found our reliance on technology for tasks like navigation may have far wider consequences, in effect causing some of the same problems in the brain that those diagnosed with dementia experience. Not only are many distracted at the wheel, their brains may be less resilient as well.

“If people stop using their brains and totally devote themselves to their hand-held devices to find their way around the world, that could have a negative effect on getting around, and spillover effects on other things like memory,” said Lynn Nadel, a neuroscientist at the University of Arizona.

GPS solves a problem unique to the human species: we lack a biological compass that can orient us in space. Nearly all other organisms known to science can navigate long distances with astonishing precision, while we’re prone to becoming lost. Humans have adapted by using observation, memory and invention to get around this problem and navigate.

Nadel and fellow researcher John O’Keefe published a landmark book in 1978 exploring the role of the hippocampus, a simple sea-horse-shaped structure of grey matter deep in the brain. They argued that cells in the hippocampus build blocks of cognitive maps, the internal representation of space that allows both rats and humans to recall routes and relationships between landmarks and orient in space.

Building on their research, scientists have learned more about the hippocampus and its role in helping us map complex spaces in our minds. They’ve also learned the hippocampus is the basis of our episodic memory, giving us the ability to recall events about our lives. When you remember something from your past, that’s your hippocampus in action.

In the early 1990s, one of the scientists studying this relationship between memory and space was Véronique Bohbot, a student of Nadel’s in Arizona. Bohbot, now a Montreal-based neuroscientist at the Douglas Mental Health University Institute and an associate professor at McGill University, became interested in the possibility that people use different structures in the brain for different strategies of navigation and began to design studies focused on one called the caudate nucleus.

The caudate nucleus operates differently than the hippocampus. Whereas the latter is involved in creating cognitive maps, the caudate nucleus is responsible for a “stimulus-response strategy.” According to Bohbot, this allows the brain to learn a series of directional cues such as “turn right” and “turn left” and create a habit of them. Effectively, we go on autopilot.

The more we use autopilot, Bohbot found, the less we rely on our hippocampus, which can shrink its grey matter volume. Several studies have found that reduced grey matter in the hippocampus is associated with cognitive deficits of aging like memory impairment, and increases the risk of atrophy, dementia, and Alzheimer’s disease.

Bohbot said she believes many of the mental impairments associated with aging may be connected to changes in how we use our brains over our lives, from navigating and exploring space as children to increasingly relying on familiar routes as adults. Over the course of adulthood, Bohbot and her fellow researchers believe, navigation behaviour becomes more automatic, with less reliance on the hippocampus. This underuse can lead to a decrease of grey matter volume.

The caudate nucleus is also located in the striatum, a brain area involved in addiction. Bohbot wanted to find out whether people who rely on a stimulusresponse strategy to navigate might show any difference in addiction behaviour from those who relied on spatial strategies. She conducted a study of 55 young adults and discovered that those who use a stimulusresponse to complete a virtual maze had double the amount of lifetime alcohol consumption, as well as more use of cigarettes and marijuana.

When we turn on the GPS on our phones and follow turn-byturn directions, we are using a classic stimulus-response strategy. Our caudate nucleus is activated and we bypass the creation of cognitive maps. Although there are no studies yet specifically testing whether using GPS when we drive or navigate can cause cognitive impairments, the risks of letting our hippocampus go unused are considerable.

“There is a use it or lose it thing about the brain,” said Nadel, who cited studies showing that London taxi drivers, who are required to memorize vast amounts of spatial information and create new routes on a daily basis to zip passengers around the British capital, have more grey matter in their hippocampus.

Bohbot says research so far is changing scientific understanding on how hippocampal volume relates to disease and aging.

“People who have a shrunk hippocampus are at risk for PTSD, Alzheimer’s, schizophrenia, depression,” Bohbot explained. “For a long time we thought the disease causes shrinkage in the hippocampus. But the shrunk hippocampus can be there before the disease.”

Forecasts predict that the number of turn-by-turn navigation app users will reach nearly 400 million in 2017, four times the number in 2011, according to the market research firm Berg Insight. With so many million people changing how they navigate, could this aspect of how we use digital devices on the move pose a public health threat?

There’s no evidence or studies to support this claim. What can be said is that frequent use of GPS might be compounding cognitive health declines. Scientists already know that several common conditions of modern life — chronic stress, untreated depression, insomnia and alcohol abuse — have been shown to affect hippocampal volume.

Bohbot encourages individuals to use and create cognitive maps as much as possible in their daily lives. This requires paying attention to one’s surroundings and landmarks, and inventing new routes and shortcuts to get to both familiar and novel destinations. Turning off the GPS, at least now and then, is one way to keep those skills engaged.

“In the past we may never have had to go on autopilot,” Bohbot said. “With GPS, you might have even less of a reason to pull out that cognitive map. The hippocampus may be lacking this requirement to work for decades when you only use it once in a while.”