Sense of agency refers to the feeling of being in control of one's actions. Previous research has demonstrated that sense of agency is produced through the sensorimotor system, which is involved in comparing internal predictions with sensory feedback in motor control. Therefore, sensorimotor deficits might impair agency through a sensorimotor system malfunction. The present study examined this hypothesis by investigating post-stroke patients who had suffered a subcortical stroke that damaged regions associated with sensorimotor function. To examine agency judgments with respect to motor control, we adopted a selfother attribution task and applied it to post-stroke patients. Participants traced a horizontal straight line and received visual feedback through a cursor on a monitor. The cursor movement reflected either the participants' actual movement or the movement of an "other" that had been previously recorded. Participants judged whether the cursor movement reflected their own movement (self) or an other's movement while they engaged in four cycles of the horizontal tracing movement. After each trial, participants reported their self-other judgment on a nine-point scale. Post-stroke patients completed the experiment with their paretic as well as their non-paralyzed upper limbs. Compared to healthy controls, patients made significantly more self-attributions of others' movements. Interestingly, such misattributions were observed in the patients' performance using both paretic and non-paralyzed upper limbs. These results suggest that post-stroke patients with sensorimotor deficits form misattributions that cannot be explained solely by the sensorimotor system's role in motor control. We discuss these misattributions in post-stroke patients in terms of cue integration theory.

Post-stroke sensorimotor deficits impair voluntary movements. This impairment may alter a person’s sense of agency, which is the awareness of controlling one’s actions. A previous study showed that post-stroke patients incorrectly aligned themselves with others’ movements and proposed that their misattributions might be associated with their sensorimotor deficits. To investigate this hypothesis, the present study compared the agency dynamics in a post-stroke patient A (PA) with sensorimotor deficits, who rarely used her paretic upper limbs in her daily life to patient B (PB), who had a paretic upper limb with almost normal functions and activity. At the second, fourth, and eighth weeks following their strokes, PA and PB completed experiments where they performed horizontal movements while receiving visual feedback, and analyzed if the visual feedback represented their own or another’s movements. Consequently, PB made no misattributions each week; whereas, PA made incorrect self-attributions of other’s movements at the fourth week. Interestingly, this misattribution noticeably decreased at the eighth week, where PA, with an improved paretic upper limb, used her limb almost as much as before her stroke. These results suggest that the sense of agency alters according to the sensorimotor deficit severity and paretic upper limb activity.

Sense of agency refers to the experience of controlling one’s actions. Studies on healthy people indicated that their self-other attribution can be realized based on prediction error which is an inconsistency between the internal prediction and sensory feedback of the movements. However, studies on patients with post-stroke sensorimotor deficits hypothesized that their self-other attribution can be based on different attribution strategies. This preliminary study examined this hypothesis by investigating whether post-stroke sensorimotor deficits can diminish the correlation between prediction errors and self-other judgments. Participants performed sinusoidal movements with visual feedback and judged if it represented their or another’s movements (i.e., self-other judgment). The results indicated that the patient who had worse upper limb sensorimotor deficits and lesser paretic upper limb activity compared with the other patient made more misattributions and showed a lower correlation between prediction errors and self-other judgments. This finding suggests that post-stroke sensorimotor deficits can impair the relationship between prediction error and self-other attribution, supporting the hypothesis that patients with such deficits can have altered strategies for the registration of agency.

[Purpose] A sense of agency and feedback control may be related when the sensory feedback is attributed to the self; however, the relationship between sense of agency and movement disorders remains unclear. Although a feedback-control task might enable the examination of this relationship, it may be difficult for patients with movement disorders to complete this task. The present study modified the feedback-control task for future clinical research. [Participants and Methods] Twenty-four healthy adults participated in the study. The basic procedure followed that of a previous study in which participants traced a target line while receiving visual feedback of their actual or fake movement. The task was modified to reduce the width of the movement area, change the shape of the line from sinusoidal to horizontal, and reduce the number of trials from 45 to 15. [Results] When participants received the visual feedback of their actual movement, the movement error significantly decreased, whereas when participants received the fake movement that represented pre-recordings of their previous own movements, the movement error significantly increased. [Conclusion] The results partially agreed with those of the previous study. This modified task might help in examining the relationship between sense of agency and movement disorders in terms of motor control.