There is a limit to multi-tasking after all. The brain is not wired to allow you to balance your chequebook while introspecting, say researchers who have practically wire-tapped a hard-to-reach region of the brain.

The research showed that groups of nerve cells in a structure called the posterior medial cortex, or PMC, are strongly activated during a recall task such as trying to remember whether you had coffee yesterday. However, these groups of nerve cells are also just as strongly suppressed when you’re engaged in solving a math problem.

The PMC, situated roughly where the brain’s two hemispheres meet, is of great interest to neuroscientists because of its central role in introspective activities, the journal Proceedings of the National Academy of Sciences reports.

“This brain region is famously well-connected with many other regions that are important for higher cognitive functions,” said Josef Parvizi, associate professor of neurology and neurological sciences at the Stanford University Medical Centre. Parvizi and his Stanford colleagues found a way to directly and sensitively record the output from this ordinarily anatomically inaccessible site in human subjects,.

By doing so, they learned that particular clusters of nerve cells in the PMC that are most active when you are recalling details of your own past are strongly suppressed when you are performing mathematical calculations.

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