Researchers have shown they can read a person's intentions from the patterns of activity in the front of their brain.
Eight participants decided privately whether to add or subtract two numbers that appeared between 2.7 and 10.8 seconds after they had made their decision. Shortly after that, a response screen appeared, featuring the two possible answers, plus two other numbers, in randomly-arranged positions.
The participants had to press a button corresponding to the number on the response screen that matched the act of subtraction or addition they had previously decided to make (thus revealing what their prior intention had been).
Crucially, because the answers and distractors were arranged randomly on the response screen, the participants could not start preparing the specific button press response they would need to make until the response screen appeared. This helped ensure relevant brain activity reflected the participants' chosen intention rather than motor preparation.
The researchers found patterns of activity in several regions of the prefrontal cortex predicted whether the participants' had chosen to add or subtract. In particular, decoding the spatial distribution of activity in the medial prefrontal cortex was able to predict the participants' intention with 70 per cent accuracy. There was no difference in overall levels of activity between the addition and subtraction decisions.
An important question for future research is whether “the medial prefrontal cortex is generally involved in encoding specific tasks during intentional choices or whether encoding in this region is specific for tasks such as the preparation of addition and subtraction”, the researchers said.