Intermuscular coherence reveals that affective emotional pictures modulate neural control mechanisms during the initiation of arm pointing movements.

Introduction: Several studies in psychology provided compelling evidence that emotions significantly impact motor control. Yet, these evidences mostly rely on behavioral investigations, whereas the underlying neurophysiological processes remain poorly understood. Methods: Using a classical paradigm in motor control, we tested the impact of affective pictures associated with positive, negative or neutral valence on the kinematics and patterns of muscle activations of arm pointing movements performed from a standing position. The hand reaction and movement times were measured and electromyography (EMG) was used to measure the activities from 10 arm, leg and trunk muscles that are involved in the postural maintenance and arm displacement in pointing movements. Intermuscular coherence (IMC) between pairs of muscles was computed to measure changes in patterns of muscle activations related to the emotional stimuli. Results: The hand movement time increased when an emotional picture perceived as unpleasant was presented as compared to when the emotional picture was perceived as pleasant. When an unpleasant emotional picture was presented, beta (ß, 15-35 Hz) and gamma (γ, 35-60 Hz) IMC decreased in the recorded pairs of postural muscles during the initiation of pointing movements. Moreover, a linear relationship between the magnitude of the intermuscular coherence in the pairs of posturo-focal muscles and the hand movement time was found in the unpleasant scenarios. Discussion: These findings reveal that emotional stimuli can significantly affect the content of the motor command sent by the central nervous system to muscles when performing voluntary goal-directed movements.

The Duration of Emotional Image Exposure Does Not Impact Anticipatory Postural Adjustments during Gait Initiation.

Previous studies have reported that anticipatory postural adjustments (APAs) associated with gait initiation are affected by emotion-eliciting images. This study examined the effect of the duration of exposure to emotional images on the APAs along the progression axis. From a standing posture, 39 young adults had to reach a table by walking (several steps) toward pleasant or unpleasant images, under two sets of conditions. In the short condition, the word "go" appeared on the image 500 ms after image onset and participants were instructed to initiate gait as soon as possible after the word go appeared. In the long condition, the same procedure was used but the word "go" appeared 3000 ms after image onset. Results demonstrated that the APAs were longer and larger for pleasant images than unpleasant ones, regardless of the condition (i.e., the duration of exposure to the images). In the same way, the peak of forward velocity of the centre of body mass (reached at the end of the first step) followed the same tendency. These results emphasized that APAs depended on image valence but not on the duration of images exposure and were consistent with those of previous studies and the motivational direction hypothesis.

Emotion, intent and voluntary movement in children with autism. An example: the goal directed locomotion.

This article focuses on the impact of intentionality on goal directed locomotion in healthy and autistic children. Closely linked with emotions and motivation, it is directly connected with movement planning. Is planning only preserved when the goal of the action appears motivating for healthy and autistic children? Is movement programming similar for autistic and healthy children, and does it vary according to the emotional valence of the object? Moving in a straight line, twenty autistic and healthy children had to retrieve a positive or aversive emotional valence object. The results suggest planning and programming are preserved in an emotionally positive situation. However, in an aversive situation, autistic children appear to have a deficit in terms of planning and sometimes programming.

Balance control and adaptation of kinematic synergy in aging adults during forward trunk bending.

The present study focuses on the organization of kinematic synergy and its adaptation to an unstable support surface during upper trunk movements in aging adults. Seven healthy aging adults (49-66 years old) were instructed to bend the trunk forward (the head and the trunk together) by about 40 degrees and to stabilize their final position, in the standard condition (both feet on the ground), and on a seesaw swinging in the sagittal plane. Kinematic synergy was quantified by performing a principal components analysis on the hip, knee and ankle angle changes during the movement. The results indicate that trunk bending was represented by a single component (PC1) in both conditions, indicating a strong coupling between the angle changes during the movement. The results also show a reorganization of the contribution of PC1 to the three angles when the balance constraints are increased in the seesaw condition. It is concluded that kinematic synergy is preserved during trunk bending in aging adults, regardless of the support conditions. It can also be adapted when the balance constraints are increased by changing the ratio between the angles, indicating a modification of interjoint coordination without modifying the movement's trajectory.