Resumo

If we make movements in order to achieve rewarding states, then the very nature of this reward should exert an influence both on movement planning and execution. Kinematics is classically thought to reflect movement planning (Bernstein, 1967). This parameter was measured in 13 volunteers during the reach and grasp of real emotional-laden (pleasant, unpleasant and neutral) objects. Polhemus Fastrak was used for recording the position and orientation of the left wrist, tracked at 30 Hz during the task execution. Two way ANOVA revealed a main effect of valence and movement phase (F(6,66)=4.9701, p<0.01) for the velocity peak parameter. Pot hoc analysis revealed that velocity peaks occurring during the movements of reaching the cup and bringing it close to the body were significantly higher for pleasant as compared to neutral (p=0.05 and p<0.01, respectively) and to unpleasant conditions (p=0.05 and p<0.01, respectively). For the movement of replacing the object on the table, velocity peaks were significantly higher for pleasant compared to unpleasant conditions (p<0.01) . We herein show that the peak velocity during a reach and grasp movement is affected by the emotional value of the object to be grabbed. Pleasant objects thus seem to associate to changes in kinematics, indicating that this affective modulation occurs at the planning level. Our results suggest that internal models of movement incorporate the object value when the movement planning aims at a pleasant or rewarding stimulus.