Revealing secret intentions in the brain
Every day we plan numerous actions, such as to return a book to a friend or to make an appointment. How and where the brain stores these intentions has been revealed by John-Dylan Haynes from the Max Planck Institute for Human Cognitive and Brain Sciences, in cooperation with researchers from London and Tokyo. For the first time they were able to “read” participants’ intentions out of their brain activity. This was made possible by a new combination of functional magnetic resonance imaging and sophisticated computer algorithms (Current Biology, Feb. 20, 2007, online: Feb. 8).
Our secret intentions remain concealed until we put them into action – so we believe. Now researchers have been able to decode these secret intentions from patterns of their brain activity. They let subjects freely and covertly choose between two possible tasks – to either add or subtract two numbers. They were then asked to hold in mind their intention for a while until the relevant numbers were presented on a screen. The researchers were able to recognize the subjects intentions with 70% accuracy based alone on their brain activity – even before the participants had seen the numbers and had started to perform the calculation.
Participants made their choice covertly and initially did not know the two numbers they were supposed to add or subtract. Only a few seconds later the numbers appeared on a screen and the participants could perform the calculation. This ensured that the intention itself was being read out, rather than brain activity related to performing the calculation or pressing the buttons to indicate the response. “It has been previously assumed that freely selected plans might be stored in the middle regions of the prefrontal cortex, whereas plans following external instructions could be stored on the surface of the brain. We were able to confirm this theory in our experiments,” Haynes explained.
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