When not focused on a specific task, the brain remains active with internal thoughts (ruminating).
by Clare Pain -
Brain cells we use to mull over our past must switch off when we do sums, say researchers, who have been spying on a previously inaccessible part of the brain.
The findings could help in the understanding of autism, ADHD and depression.
The research, reported in the Proceedings of the National Academy of Sciences, boosts our understanding of how the brain switches from being internally focused (ruminating) to focusing on a task in the outside world.
The Stanford University team, led by Professor Josef Parvizi, studied the posteromedial cortex (PMC) – a very inaccessible region of the cortex buried deep in the crack between the brain’s two hemispheres.
“It’s an area that’s extremely active when the brain is resting”, says Parvizi, who says much of the research was done by an Australian post-doc, Dr Brett Foster.
When we are not actively concentrating on something, the brain is still thinking – it ruminates or ‘free-wheels’, mulling over past actions and imagining the future. “The PMC is the hub of all these rumination processes,” says Parvizi.
A procedure used on eight patients with severe epilepsy gave Parvizi’s group a valuable opportunity to “go into the hub and spy on the cells”.
Anti-epileptic drugs had failed to help these patients, so they had electrodes implanted widely over their brains in an attempt to find the seizure source – with the aim of then excising the problem region.
Some of these electrodes had been implanted in the PMC and, while the patients lay bored in bed waiting for seizures to occur, they allowed Parvizi’s group to eavesdrop on their brain cells.
The patients were asked to evaluate simple statements about their recent experience such as “I had a cup of coffee this morning” by pressing true or false buttons.
Dealing with these kinds of statements about their own personal history made the PMC cells extremely active – showing it is involved in processing autobiographical memory.
On the other hand, assessing whether a sum like “23 + 8 = 34″ was true or false strongly reduced PMC cell activity.
“What we discovered was fascinating,” says Parvizi. “The same group of neurons that are very very active during a rumination process – exactly the same neurons – have to be shut down in order to solve a maths equation.”
Read more at Brain ‘switches between maths and memory.
[Via ABC News]
