novembro 15, 2008

The secret life of the brain

People have long envisaged the brain as being like a computer on standby, lying dormant until called upon to do a task, such as solving a Sudoku, reading a newspaper, or looking for a face in a crowd.
This amazing organ, which accounts for only 2 per cent of our body mass but devours 20 per cent of the calories we eat, fritters away much of that energy doing, as far as we can tell, absolutely nothing.
Some call it the neural dynamo of daydreaming. Others assign it a more mysterious role, possibly selecting memories and knitting them seamlessly into a personal narrative. Whatever it does, it fires up whenever the brain is otherwise unoccupied and burns white hot, guzzling more oxygen, gram for gram, than your beating heart.
Daydreaming may sound like a mental luxury, but its purpose is deadly serious: Buckner and his Harvard colleague Daniel Gilbert see it as the ultimate tool for incorporating lessons learned in the past into our plans for the future. So important is this exercise, it seems, that the brain engages in it whenever possible, breaking off only when it has to divert its limited supply of blood, oxygen and glucose to a more urgent task.

Each day we soak up a mountain of short-term memories but only a few are actually worth adding to the personal narrative that guides our lives.

Raichle now believes that the default network is involved, selectively storing and updating memories based on their importance from a personal perspective - whether they're good, threatening, emotionally painful, and so on. To prevent a backlog of unstored memories building up, the network returns to its duties whenever it can.the default network's pattern of activity is disrupted in patients with Alzheimer's disease.

The default network also turns out to be disrupted in other maladies including depression, attention-deficit hyperactivity disorder (ADHD), autism and schizophrenia.
The meditating mind

New Scientist , 05 November 2008 by Douglas Fox

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