Objective: The study investigated the difference between simple and complex tasks influence on the effectiveness of mirror visual feedback (MVF). Furthermore, it was investigated if higher subjective ratings of ownership feelings of the mirror reflection were related to an improved MVF effect.
Methods: 23 health participants (12 males, 11 females) participated in six condition; neutral -, enlarging -and without mirror(control condition) with both simple and complex tasks. The design was a repeated measure design therefore all subjectsparticipated in all conditions in a random order. After each condition, the effect of MVF was measured as response time (RT) to hand laterality, andthe experienced ownership and agency feelings of the mirror reflection was rated in a questionnaire.
Results: There was seen no significant difference in RT between neutral, enlarging and without mirror conditions. There was a significantly faster RT after complex tasks compared to simple tasks in the neutral and enlarging mirror conditions (p = 0,041). Ratings of ownership feelings differed significantly between mirror and control conditions (p < 0,001),and between simple and complex task (p = 0,002), but ownership did not correlate with changes in RT. Even if the participants were divided into two groups;high or low ownership ratings, there was not seen any relationship to RT.When the participants were divided two groups; high or low rated agency, the experienced sense of agencycorrelated positive with RT in two conditions; enlarging mirror simple tasks (p = 0,047) and without mirror complex tasks (p = 0,044). Ratings of ownership and agency were positivecorrelated.
Conclusions: The missing ability to achieve significant differences in RTs between mirror and without mirror conditions indicates that the MVF intervention did not influence the participants. Explanations for this might be that MVF was applied too short to make any changes to the motor control system of healthy participants, that the effects were not strong enough to be visible in laterality, or that laterality is not affected by MVF. Complex tasks influenced hand laterality,which suggests, it would be beneficial to implement in MVF, although the influence of complex tasks on hand laterality might be independent from mirror illusion effects. Nothing in the current study supported that feelings of ownership were necessary to achieve an effect from MVF.The experienced sense of agency might be predictable for MVFs effect under certain condition, but the results was too ambiguous to base conclusions on.