How the effects of actions become our own

Abstract

Every day, we do things that cause effects in the outside world with little doubt about who caused what. To some, this sense of agency derives from a post hoc reconstruction of a likely causal relationship between an event and our preceding movements; others propose that the sense of agency originates from prospective comparisons of motor programs and their effects. Using functional magnetic resonance imaging, we found that the sense of agency is associated with a brain network including the pre-supplementary motor area (SMA) and dorsal parietal cortex. Transcranial magnetic stimulation affected the sense of agency only when delivered over the pre-SMA and specifically when time-locked to action planning, rather than when the physical consequences of the actions appeared. These findings make a prospective theory of the sense of agency more likely.

Fig. 1. Behavioral results (fMRI experiment) showing the intentional binding effect at 200-ms action-outcome delay.

Time compression values for the active and passive conditions recorded at 200, 400, and 600 ms of action-outcome delay. Error bars = SE; asterisks indicate significant results at P < 0.05, Bonferroni corrected. TC is visualized as the percentage of the time delay of the outcome.

Fig. 2. fMRI results showing a significant association between the magnitude of the intentional binding effect and pre-SMA/parietal activity.

Linear regression analysis between the BOLD activity recorded in the left pre-SMA and in the right parietal site and the differential time compression values (active trials − passive trials) when the action-outcome delay was 200 ms, and the intentional binding was observed (see also Table 1).

Fig. 3. Results of rTMS experiment 1, in which rTMS was applied during the action-planning phase.

rTMS applied during the action planning. (Top left) Time compression values recorded before rTMS for active and passive trials: The intentional binding was present only when the action-outcome delay was 200 ms. (Top right) TC values recorded during rTMS over the pre-SMA: The intentional binding was present also when the action-outcome delay was 400 ms. (Bottom left) TC values recorded during rTMS over the parietal site: The intentional binding was present only when the action-outcome delay was 200 ms. (Bottom right) TC values recorded during rTMS over the occipital control site: The intentional binding was present only when the action-outcome delay was 200 ms. (Error bars = SE; asterisks indicate significant effects; P < 0.05, Bonferroni-corrected); TC is visualized as the percentage of the time delay of the outcome.

Fig. 4. Graphical illustration of an experimental trial of the fMRI experiment for active and passive conditions.

During active trials, the picture of a turned-off light bulb with its base colored in green was shown. Participants were instructed to turn the light bulb on by pressing a button with their right index finger. After the button press, the light bulb went on with a variable delay of 200, 400, or 600 ms. Participants were then asked to rate the perceived temporal interval between their button press and the lighting of the light bulb.

Fig. 5. Graphical illustration of an experimental trial of each rTMS experiment for active and passive conditions.

In experiment 1, rTMS was applied during the action planning phase (at the appearance of a turned-off light bulb indicating an active or passive trial, depending on the green/red color of the base). In experiment 2, rTMS was applied at the appearance of the physical consequence of the button press (at the lighting of the light bulb). In the figure, the rTMS coils are placed according to the time points of rTMS delivery.