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publicado em 12/11/2010 às 15h00:00
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City life and the brain

 
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For the first time in history, more people live in cities than in rural areas. According to the United Nations, that urban head count tallies up to more than half of the world’ s 6.7 billion people. While city life may offer many benefits ready access to social and cultural events, more employment opportunities, and the promise of higher living standards, as examples research does show that city life can have drawbacks. For one thing, it’ s hard on the brain.

Scientists who have begun to look at how the city affects our brains have uncovered some surprising findings, including evidence that city life can impair basic mental processes, such as memory and attention. A study conducted by University of Michigan researchers in 2008 found that simply spending a few minutes on a busy city street can affect the brain’ s ability to focus and to help us manage self-control.

In that study, one group of participants strolled in a park, while another perambulated along busy city streets. After undergoing a battery of psychological tests, the people who walked the city streets scored significantly lower on attention and working-memory tests compared to those participants who ambled in the park. The researchers concluded that the stimuli of city life traffic, neon lights, sirens, and pedestrian-packed sidewalks direct our attention to things that are compelling, but only fleetingly so, and that this alteration of focus can occur at a pace that leaves us mentally exhausted.

" On a busy city street, it’ s probably more adaptive to have a shorter attention span, " says Sara Lazar, PhD, an HMS instructor in psychology and director of the Massachusetts General Hospital Laboratory for Neuroscientific Investigation of Meditation. " If you’ re too fixated on something, you might miss a car coming around the corner and fail to jump out of the way. "

Some people might call these stimuli distractions, but as Lazar points out, they are actually vital pieces of information. Yet these stimuli do use up a lot of the brain’ s natural processing power. The result is something called directed attention fatigue, a neurological symptom that occurs when our voluntary attention system, the part of the brain that allows us to concentrate in spite of distractions, becomes worn down. People suffering from directed attention fatigue can experience short-term feelings of heightened distraction, impatience, or forgetfulness. When the condition is severe enough, people can exhibit poor judgment and feel increased levels of stress.

Fortunately, there are quick, easy fixes to help the brain restore its ability to focus. Studies show that spending a short period of time even one as brief as 20 minutes in a more natural setting can help the brain recover from the stresses of city life. That may be why urban greenways such as Central Park in New York City, Hyde Park in London, and the Emerald Necklace in Boston remain such popular venues they allow city dwellers a place to escape the turbulence around them.

The benefits of a room with a verdant view can be found in studies involving hospitalized patients and residents of public housing complexes. Patients staying in hospital rooms that looked out on trees, for example, were found to recover more quickly than patients without an arboreal view. Similar results were found in studies involving women residing in public housing projects; those whose apartments overlooked grassy areas reported they could more easily focus on the tasks of daily life.

This nature brain symbiosis may be the result of a concept known as attention restoration theory, which was developed by environmental psychologists Rachel and Stephen Kaplan in their book, The Experience of Nature: A Psychological Perspective. According to this concept, people can concentrate better after spending time in nature or even after simply looking at pictures of nature. Watching a beautiful sunset or the nesting of birds in a tree doesn’ t demand the type of attention from the brain that filtering a multitude of competing stimuli on a bustling city street does. Natural vistas allow the brain’ s attention circuits to refresh.

In her laboratory at Mass General, Lazar is using neuroimaging techniques to study cognitive changes associated with meditation and yoga, practices that are, like nature, calming to mind and body. Lazar and her colleagues have found that people who meditate develop denser, thicker networks of neurons in the prefrontal cortex and right anterior insula of their brains. These areas govern attention and sensory processing.

She says such findings may help explain why urban life can affect our ability to hold things in memory. Memory, she says, relies on the hippocampus, a neural region that is sensitive to cortisol, a hormone secreted by the adrenal glands. Cortisol is linked with stress and secretion of it increases during the body’ s fight-or-flight response to fear or danger.

" If people are stressed about basic survival, they will have more cortisol and a smaller hippocampus, and thus potential difficulties with memory formation," says Lazar. " Moving to a quieter place could help reduce stress, which in turn can reduce cortisol levels and create conditions conducive to neuroplasticity. " Neuroplasticity describes the brain’ s ability to form new neuronal connections to compensate for injury or changes in one’ s environment.

If you could use a break from the strain of city life, but don’ t see your future including a move to a less demanding environment, Lazar says you may want to consider taking up or increasing your practice of yoga or meditation. Your brain, and your lifestyle, could benefit immensely.

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