Inhibition of imitative behaviour and social cognition

Abstract

There is converging evidence that the observation of an action activates a corresponding motor representation in the observer through a 'mirror-matching' mechanism. However, research on such 'shared representations' of perception and action has widely neglected the question of how we can distinguish our own motor intentions from externally triggered motor representations. By investigating the inhibition of imitative response tendencies, as an index for the control of shared representations, we can show that self-other distinction plays a fundamental role in the control of shared representations. Furthermore, we demonstrate that overlapping brain activations can be found in the anterior fronto-median cortex (aFMC) and the temporo-parietal junction (TPJ) area for the control of shared representations and complex social-cognitive tasks, such as mental state attribution. In a functional magnetic resonance imaging experiment, we functionally dissociate the roles of TPJ and aFMC during the control of shared representations. Finally, we propose a hypothesis stating that the control of shared representations might be the missing link between functions of the mirror system and mental state attribution.

Figure 1.

(a) Two frames depicted from the imitation-inhibition task. Participants have to respond to a number presented between the index and a middle finger of a video-taped hand while observing congruent or incongruent finger movements. (b) Brain activation for the contrast of incongruent versus congruent movements (Brass et al. 2005) plotted in red on a meta-analysis of the TPJ and the aFMC (blue, mentalizing; green, self-referential processing; yellow, agency processing). (For display purposes the activations of the social cognitive tasks are plotted with the same x-coordinate as the activations from the imitation-inhibition task.)

Figure 2.

Schematic drawing of the modified imitation-inhibition task. The left side depicts the series of events in the simultaneous condition where participants had to imitate the observed movement when a green cross appeared and had to counter-imitate when a red cross appeared. The right side illustrates the delayed condition where participants had to respond to a number and the response triggered a congruent or incongruent movement.

Figure 3.

The left part shows the brain activation of incongruent versus congruent trials in the simultaneous condition. On the right, the signal strength analysis in TPJ and aFMC is displayed. The mean beta values in these two areas are plotted as a function of MAPPING (congruent versus incongruent) and DELAY (simultaneous, delayed).