On building the brain YOU want

Taxi drivers' brains 'grow' on the job

Cabbies' brains adapt to hold "the knowledge"

Cab drivers' grey matter enlarges and adapts to help them store a detailed mental map of the city, according to research.

Taxi drivers given brain scans by scientists at University College London had a larger hippocampus compared with other people. This is a part of the brain associated with navigation in birds and animals.

The scientists also found part of the hippocampus grew larger as the taxi drivers spent more time in the job. 

I never noticed part of my brain growing - it makes you wonder what happened to the rest of it. David Cohen, taxi driver

"There seems to be a definite relationship between the navigating they do as a taxi driver and the brain changes," said Dr Eleanor Maguire.

However driving round London streets is stresful

and stress creates CORTISOL, so a little on that.

The stress hormone, cortisol, is public health enemy number one. Scientists have known for years that elevated cortisol levels: interfere with learning and memory, lower immune function and bone density, increase weight gain, blood pressure, cholesterol, heart disease.

Cortisol is released in response to fear or stress by the adrenal glands as part of the fight-or-flight mechanism. The fight-or-flight mechanism is part of the general adaptation syndrome defined in 1936 by Canadian biochemist Hans Selye of McGill University in Montreal. He published his revolutionary findings in a simple seventy-four-line article in Nature, in which he defined two types of "stress": eustress (good stress) and distress (bad stress).

Eustress creates a "seize-the-day" heightened state of arousal, which is invigorating and often linked with a tangible goal. Cortisol levels return to normal upon completion of the task. Distress, or free-floating anxiety, doesn't provide an outlet for the cortisol and causes the fight-or-flight mechanism to backfire. Ironically, our own biology — which was designed to insure our survival as hunters and gatherers — is sabotaging our bodies and minds in a sedentary digital age. What can we do to defuse this time-bomb?