Who does what? Neural representations of identity and ownership of one's own and a partner's subtasks

In daily life, humans often coordinate their actions to perform collaborative tasks (Sebanz, Bekkering, & Knoblich, 2006). Previous studies have shown that people co-represent different parts of a general task when they carry it out together, even if representing the partner's subtask is not necessary to perform their own part of the task (e.g., Atmaca, Sebanz, & Knoblich, 2011). However, it is still an open question how these task representations are encoded at the neural level. In this study, we examined task encoding when people have to work together to achieve a common goal. Specifically, we investigated where and how the human brain represents a task that is performed by the subject or by their partner. Twenty-six participants played a collaborative game in pairs. In the game, they had to coordinate to reach a common goal. For each pair, each subject performed the game once while undergoing functional magnetic resonance imaging (fMRI) and once using a computer in a room adjacent to the fMRI scanner. Each participant performed one part of a shared task. To win the game, the players had to consider both their own and the other's subtask. The shared task consisted in moving two pawns on a graphic path to match their positions. Each player moved one of the two pawns as specified by the subtask assigned to them. The players had to compute the combination of moves that allowed both of them to reach the goal. Importantly, the same subtask was assigned to one subject on some trials and to their partner on other trials. This paradigm allowed us (i) to identify neural representations of one's own and the other's subtask and (ii) to evaluate whether task representations differ depending on whom the task is assigned to (by comparing trials in which the same subtask was assigned to the subject vs. to their partner). We applied multivariate decoding methods (e.g., Haynes & Rees, 2006) to fMRI data. Preliminary results show that the identity of the subtask assigned to either the subject or to their partner is represented in distinct frontal and parietal regions: ventrolateral and rostrolateral prefrontal cortex (PFC) encoded only the identity of one's own task, while medial PFC and postcentral gyrus specifically represented the identity of the other's subtask. Information about who performed a specific subtask was contained in orbitofrontal cortex, superior parietal lobule, and inferior parietal lobule. These findings suggest that task ownership determines how information is represented across the brain.