Self-initiated task selection is predicted by multi-voxel pattern activity in medial prefrontal and parietal cortices
Based on clinical observations in brain-damaged individuals, it has been known for a long time that the brain mechanisms underlying externally triggered and internally initiated goal-directed behavior must be different, as there are patients who do very well when the clinician asks them to carry out various cognitive and behavioral tasks, including ones that measure so-called executive functions, however, the very same patients might be unable to take initiative and make their own internally driven choices to pursue meaningful goals on their own. In neuroimaging studies, the neural basis of switching from one task to another has been mostly studied using cue-stimulus triggered paradigms. What has remained less well known, due in large part to obvious methodological challenges in measuring the timing of “internal triggers”, is which brain mechanisms underlie genuine internally driven task selection.
In their recent study, Soon et al. (2013) used functional magnetic resonance imaging in a group of 34 healthy volunteers to study brain mechanisms that precede internally initiated task selection. The authors set up a paradigm where subjects voluntarily engaged into mental tasks of adding or subtracting. Brain hemodynamic activity patterns preceding task initiation / selection were then examined using multivoxel pattern analysis algorithms. It was observed that intention to switch task could be decoded from patterns of hemodynamic activity within medial prefrontal cortex and parietal cortex, areas partly overlapping with the so-called default-mode network, as early as four seconds before the subjects self-estimated having become consciously aware of their choices.
These highly important findings not only disclose brain areas that underlie internally driven task selection, but also provide important methodological advances that can be utilized in further studies on this important research question. Notably, it was shown that specifically the distributed pattern of brain activity held the information that predicted the initiation of task switch, the overall amplitudes of hemodynamic activity within the medial prefrontal and parietal cortices failed to do so. The task paradigm devised by the authors is also one that can be readily modified for further studies of the neural basis of voluntary task selection.
Reference: Soon CS, He AH, Bode S, Haynes JD. Predicting free choices for abstract intentions. Proc Natl Acad Sci USA (2013) 110: 6217-6222. http://dx.doi.org/10.1073/pnas.1212218110