Past research had indicated that activity in the area of the prefrontal cortex increases when humans engage in goal-related neural processing, but it has been unclear whether patterns of activity might encode an individual's current intention. The observed goal-related activity might also (or, alternatively) represent other processes, such as preparing for a motor response, accessing memories of past related responses, or bearing in mind the choice of responses available.
To address the question of whether intention might be reflected in prefrontal cortical activity, the researchers in the new work used functional magnetic resonance imaging (fMRI) to assess brain activity while subjects concentrated on their choice of intended mental action, but prior to execution of the action. Specifically, subjects were free to choose between adding or subtracting two numbers and were asked to hold in mind their intention until numbers were presented on a screen, along with a choice of outcomes (one of which was correct for the addition choice, one correct for the subtraction choice). Subjects then selected the correct answer according to their planned task, revealing their intended action.
The researchers found that during the delay between the subjects' choice of task and execution of the task, it was possible to decode from activities in two regions of the prefrontal cortex which of the two actions (addition or subtraction) individuals had chosen to pursue. Different patterns of activity were seen du ring actual execution of the task, showing that regionally distinct neural substrates were involved in task preparation and execution. Decoding of intentions was most robust when activity patterns in the medial prefrontal cortex were taken into account, consistent with the idea that this region of the brain participating in the reflection of an individual on his or her own mental state.