Scientists are beginning to discover that city life is hard on the brain, where the need continuously to process multitudes of fleeting but compelling stimuli can impair mental processes like memory and attention and leave us mentally exhausted.

Dr Sara Lazar, director of the Massachusetts General Hospital Laboratory for Neuroscientific Investigation of Meditation in Boston, whose work is sponsored by the National Institutes of Health and the Center for Disease Control and Prevention, says that “on a busy city street, it’s probably more adaptive to have a shorter attention span”.

Some people might say the stimuli that bombard us daily in city life are just a distraction, but Lazar said they could contain vital information, so we have to pay attention to them, even though they use up a lot of the brain’s natural processing power.

“If you’re too fixated on something, you might miss a car coming around the corner and fail to jump out of the way,” said Lazar, in a recent statement from Harvard Medical School.

Lazar calls the drain on brain power from attending continuously to stimuli like those that surround city dwellers “directed attention fatigue“, a neurological state that occurs when our voluntary attention, the part of the brain that we use to concentrate on particular stimuli while ignoring distractions, gets worn down.

The symptoms of directed attention fatigue include feelings of heightened distraction, impatience and forgetfulness. The more severe form can also lead to poor judgement and increased levels of stress.

But, there are ways to overcome this and refresh the brain, and it can be as simple as going for a walk in the park.

Researchers at the University of Michigan in Ann Arbor published a study in 2008 that compared the effect of interacting with nature versus interacting with urban environments.

Dr Marc Berman, a research fellow in cognitive neuroscience, and colleagues, found that even spending a few minutes on a busy city street can affect the brain’s ability to focus and manage self-control, whereas walking in nature or just looking at photographs of nature can improve directed-attention abilities.

They invited one group of volunteers to stroll in a park and another to walk some busy city streets. The group that walked in the parked scored higher in psychological tests of attention and working memory than the group that walked the city streets.

They suggested this validated the idea that spending time in nature environments refreshes the city-dweller’s brain. The theory behind it, called attention restoration theory (ART) is that nature presents us with “intriguing” stimuli that engage our senses in a “bottom-up” fashion, allowing the “top-down” directed attention required to look out for cars and other hazards a chance to rest and recuperate.

ART was first proposed in 1989 in the book The Experience of Nature: A Psychological Perspective, by environmental psychologists Rachel and Stephen Kaplan (one of the co-investigators in Berman’s study), who maintained that spending time in natural environments allows the brain’s attention circuits to refresh.

Studies of patients in hospital and people living in housing complexes have also described the benefits of living with a view of natural greenery. For example patients who could see trees from their hospital beds recovered more quickly than those who could not, and women living in high rise apartments could focus more easily on daily tasks when they had a view of grassy areas.

Lazar and her team of neuroscientists at Massachusetts General use neuroimaging to see what happens in the brain when people practise activities like meditation and yoga, which have a similar calming effect as being with nature.

In one research project they assessed cortical thickness in 20 volunteers with extensive experience of “insight” meditation, which involves focussing attention on internal experiences, and in another group of matched controls.

They found that brain regions associated with “attention, interoception and sensory processing” were thicker in the meditation practitioners, including the prefrontal cortex and right anterior insula. They found that this difference was more pronounced in the older participants, suggesting that meditation might offset the thinning of the cortical regions of the brain that occur as we age.

Lazar said city life may also affect our brains in other ways, for example in terms of the effects of stress on memory. When we are stressed, our bodies are in a state of flight or fight, which increases levels of cortisol, which in turn affects the function of the hippocampus, a part of the brain that is important for memory.

She said moving to a quieter place could help reduce stress, which brings down cortisol levels and encourages “neuroplasticity”, the brain’s ability to form new neural connections.

For the first time in human history, people living in cities outnumber those living in rural environments. The United Nations figures show that of the 6.7 billion humans in the world, more than half are urban dwellers.

While living in the city has many attractions, with more job opportunities, social and cultural activity, and probably higher standards of living, there are drawbacks, and as these studies show, the strain on the brain is one of them.

However, before we assume that the answer is to pack our bags and retreat to a less demanding environment, perhaps we should take up or increase our yoga or meditation practice, and go for more walks in the park.

Harvard Medical School Press Release (9 Nov 2010).
Marc G. Berman, John Jonides, and Stephen Kaplan, The Cognitive Benefits of Interacting With Nature, Psychological Science December 2008 19: 1207-1212.
Massachusetts General Hospital, Meditation Research website.

Written by: Catharine Paddock, PhD