The neural mechanisms related to the ability of humans and non-human primates to interact through joint-action are still poorly investigated. In the domain of motor functions, the study of goal-directed movement showed that no obligatory relationship exists between neural activity and movement, but rather movement-related activity is context-dependent and linked to different cognitive states. So far, neural activity in different cortical areas has been studied in a single brain in action, thus missing all information typical of interacting brains through a joint action task. Two monkeys sat together in front of a display and they were trained in a center-out task in two intermingled conditions. In the first (SELF), each monkey had to move individually a visual cursor from a central position toward 8 different peripheral targets, by applying a force on an isometric joystick while its partner observed the action. In the second condition (cooperative joint action: COOP), both monkeys had to move their cursors together toward the same peripheral target, under the constraint of a maximum inter-cursor distance limit, which was visualized as an outlined circle incorporating the two cursors. Thus, in this context monkeys had to cooperate to reach a common goal. Extracellular single-unit activity (SUA) was recorded from premotor cortex (PM) and inferior parietal lobule (IPL), simultaneously from homologous areas of both monkeys by using two multiple-electrode arrays. Preliminary results showed that kinematic parameters, such as amplitude and direction of the force applied on the joystick, were overall similar in the COOP and SELF conditions. However, analysis of temporal aspects related to COOP trials showed a tendency of each monkey to adapt its own behavior in order to accommodate partner’s behaviour. In 540 PM and 258 IPL neurons studied during Reaction- and Movement Time, a 2-way ANOVA showed a significant difference of SUA between SELF and COOP conditions in 28.5 % PM and 22.1% IPL cells, and between final target directions in 42.6% PM and 39.2 % IPL cells with an interaction factor that resulted significant in 13.7% PM and 14.3% IPL cells. Therefore, in these areas similar actions performed in different social contexts (such as in absence or presence of social interactions), modulates SUA in a different way. These findings represent a first step toward the description of the neural operations underlying motor functions in a cooperative context and suggest that within this action cooperation network different areas encode joint-action during different behavioural epochs.
Neural activity associated to joint-action during social cooperation in frontal and parietal cortex of macaque monkeys / F., VISCO COMANDINI; FERRARI TONIOLO, Simone; Papazachariadis, Odysseas; Caminiti, Roberto; BATTAGLIA MAYER, Alessandra. - ELETTRONICO. - (2013). (Intervento presentato al convegno Annual meeting Soc for Neuroscience tenutosi a San Diego, USA nel Nov 2013).