Urbanized Brains

Across the globe there is population drift towards the cities. The drift is rapid and by mid-century more than two-thirds of the people on the planet will be nicely urbanized. The size of cities is increasing all the time as they fill with oligarch-wannabes demanding the good life filled with luxury goods and pampered by doubtful services.

The scramble to survive in those seething masses is stressful. Schizophrenia is on the rise, as is anxiety and depression. Just being born in the city, even we subsequently break free, has our brains sensitized to react anxiously. Meyer-Lindenberg and a large team have carried out an fMRI study of people from different environments who were being stressed (1).

The age of the participants ranged from 18 to 80. Some were urban born, some were not and some were currently city dweller and some not. With their heads in the big magnet, the subjects were plied with nasty little arithmetic problems. That in itself would stress most of us, but with feedback telling the subjects to hurry, and the problems manipulated to ensure that nobody did better than get somewhere between 25 and 40% as a score, the amygdala and cingulate cortex of each subject lit up.  Some more like Christmas trees than others.

Recall that the cingulate cortex regulates the amygdala. That part of the brain was shown to be more active with those who had spent the most time as kids in cities. When your amygdala is lit up, you are feeling threatened and stressed. It’s not just nasty sums that lights up your amygdalae (remember they come in pairs but not necessarily of equal size), but people getting too close and personal get it excited too. Binge drinking is bad for you, of course, and it damages your amygdala. On the other hand working hard on expanding you social network can increase its size and that is likely to help you be nice to your neighbors.

All this leaves us with an intriguing question. How do we build sustainable cities, which won’t get our amygdalae flashing like the light on an ambulance rushing to the ER?

  1. http://www.nature.com/nature/journal/v474/n7352/full/nature10190.html

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