The organization of the movement depends mainly on the anticipation of its sensory and emotional consequences.

Two sources of emotions influence directed actions, namely, those associated with the environment and those that are consequences of the action. The present study examines the impact of these emotions on movement preparation. It invokes theories from psychology, i.e., ideomotor theory and motor control's cognitive approach through movement analysis. In addition to their action readiness, emotions related to the environment can interfere with actions directed towards a goal. However, intentional action involves a goal that will cause satisfaction when achieved. While most studies consider each emotion's influence separately, few studies confront them to study their respective impact. In the current study, thirty-two right-handed young adults reach for a left target with a stylus that will reduce or enlarge an emotional picture that is initially present (nontarget stimulus). Kinematic analyses show that anticipating the pointing's emotional consequences impacts the final pointing position. All other results emphasize the impact of reducing or enlarging on the preparation and control of movement depending on the direction of movement. The emotional consequences of the action is a weighting factor that is relevant to the action goal and subject's intention, but it is less important than the action's visual consequences.

Age-related differences in processes organizing goal-directed locomotion toward emotional pictures.

Previous studies yielded evidence for an interaction between age and valence in numerous cognitive processes. But, to date, no research has been conducted in the field of motor skills. In this study, we examined the age-related differences in the organization of an emotionally goal-directed locomotion task. Faced with a pleasant, unpleasant, or neutral picture displayed to the side of a stop button, younger and older adults were instructed to walk toward the button (intermediate goal) and push it to turn-off the picture (final goal). Kinematic and ground reaction forces were recorded. The main findings indicated that older adults' response times (RTs) did not differ across the valence picture. The fastest RTs were found in younger adults when faced with pleasant pictures, suggesting that older people may focus either on intermediate or final goals, depending on their value of pleasantness, and prioritize positive goals. We also found that the spatial coding of locomotion (trajectory and final body position) was affected in the same way by the valence of the intermediate goal in both age groups. Taken together, these findings provide new perspectives regarding the potential role of the emotional valence of the intermediate and final goals on the cognitive processes involved in action coding, such as in mental representations of action in older adults.

When locomotion is used to interact with the environment: investigation of the link between emotions and the twofold goal-directed locomotion in humans.

Walking as a means to interact with the environment has a twofold goal: body displacement (intermediate goal) and the future action on the environment (final representational goal). This involves different processes that plan, program, and control goal-directed locomotion linked to motivation as an "emotional state," which leads to achieving this twofold goal. The aim of the present study was to determine whether emotional valence associated with the final representational goal influences these processes or whether they depend more on the emotional valence associated with the intermediate goal in young adults. Twenty subjects, aged 18-35 years, were instructed to erase an emotional picture that appeared on a wall as soon as they saw it. They had to press a stop button located 5 m in front of them with their right hand. Their gait was analyzed using a force platform and the Vicon system. The main results suggest that the emotional valence of the intermediate goal has the greatest effect on the processes that organize and modulate goal-directed locomotion. A positive valence facilitates cognitive processes involved in the temporal organization of locomotion. A negative valence disturbs the cognitive processes involved in the spatial organization of the locomotion and online motor control, leading to a deviating trajectory and a final body position that is more distant from the stop button. These results are discussed in line with the motivational direction hypothesis and with the affective meaning of the intended response goal.

Emotions and voluntary action: what link in children with autism?

This research focuses on the impact of emotions--defined as "motivational states"--on the organization of goal directed locomotion in children with autism. Walking toward a goal involves both cognitive processes responsible for movement planning and automatic processes linked to movement programming. To these processes, motivation leading to achieving the goal is added. For some authors, a deficit of planning and/or programming processes is highlighted in autism. Others stand for some impairment of the emotional system. The aim of this research is to link these two viewpoints and to determine if, in children with autism, the organization of locomotion is affected by a positive/aversive emotion conferred to an object to fetch. Twenty-nine children participated in the study (11 children with autism--mean age 122 months; 9 mental age-matched controls--mean age 36 months; and 9 chronological age-matched controls--mean age 122 months). They were instructed to go and get a positive or aversive emotional valence object located straight ahead, at 30° to the right or straight ahead then moved at mid-distance to the right. Gait analysis was performed using the Vicon system. The main results suggest that a positive emotional context promotes the cognitive processes involved in movement planning while an aversive emotional context blocks it or disturbs it in children with autism. No emotions effect is observed on movement programming. It is suggested that emotions triggered off and modulated movement planning and that the deficit observed was related to a developmental impairment rather than to a developmental delay.

Effect of aging on the coordination between equilibrium and movement: what changes?

This investigation studies the effect of aging on the coordination between equilibrium and trunk movement. Eight young adults and seven adults at the end of middle age bent their trunk forward and stabilized their position. The center of mass shift was studied as an indicator of equilibrium control as was the electromyographic pattern of the main muscles involved in the movement. The kinematic strategy responsible for both the movement and equilibrium control was quantified by performing a principal components analysis on the hip, knee, ankle angle changes occurring during the movement. We observed that the effect of aging can be detected early. It is not expressed as a deterioration of equilibrium control but rather as "over control". The kinematic strategy is modified, the central command adapted. These results could express the onset of a lesser ability to simplify the coordination between equilibrium and movement as young adults leading to its deterioration in the elderly.

Kinematic synergy adaptation to an unstable support surface and equilibrium maintenance during forward trunk movement.

The aim of this investigation was to study the adaptation to an unstable support surface of kinematic synergy responsible for equilibrium control during upper trunk movements. Eight adult subjects were asked to bend their upper trunk forward to an angle of 35 degrees and then to hold the final position for 3 s, first in a standard condition, with two feet on the ground and the second, on a rocking platform swinging in the sagittal plane. The movement characteristics (duration, amplitude, and mean angular velocity of the trunk), the time course of the antero-posterior center of mass (CM) shift during the movement, and the EMG pattern of the main muscles involved in the movement were studied under the two experimental conditions. Kinematic synergy was quantified by performing a principal component analysis on the hip, knee, and ankle angle changes occurring during the movement. The results indicate that (1) the CM shift from the very onset of the movement remains controlled during performance of the forward trunk movement when the equilibrium constraints were increased; (2) the principal component analysis of the hip, knee, and ankle angle changes occurring during the movement showed a transition from one principal component (PC(1)) in the standard condition to two components in the rocking platform condition; (3) the greatest contribution of PC(1) (weight coefficients) was located at the hip level in both the standard and rocking platform conditions, while the greatest contribution of PC(2) in the rocking platform condition was located at the ankle level; and (4) the EMG pattern underlying kinematic synergy is modified. It is concluded that a simple adaptation of kinematic synergy by changing the weight coefficients of each pair of joints participating in the movement is no longer sufficient when the equilibrium constraints increase and, rather, disturbs equilibrium. The CNS has to provide two parallel controls, one to perform the trunk movement and the other to preserve equilibrium.

Goal directed locomotion and balance control in autistic children.

This article focuses on postural anticipation and multi-joint coordination during locomotion in healthy and autistic children. Three questions were addressed. (1) Are gait parameters modified in autistic children? (2) Is equilibrium control affected in autistic children? (3) Is locomotion adjusted to the experimenter-imposed goal? Six healthy children and nine autistic children were instructed to walk to a location (a child-sized playhouse) inside the psychomotor room of the pedopsychiatric centre located approximately 5 m in front of them. A kinematic analysis of gait (ELITE system) indicates that, rather than gait parameters or balance control, the main components affected in autistic children during locomotion are the goal of the action, the orientation towards this goal and the definition of the trajectory due probably to an impairment of movement planning.

Kinematic synergy adaptation to microgravity during forward trunk movement.

The aim of the present investigation was to see whether the kinematic synergy responsible for equilibrium control during upper trunk movement was preserved in absence of gravity constraints. In this context, forward trunk movements were studied during both straight-and-level flights (earth-normal gravity condition: normogravity) and periods of weightlessness in parabolic flights (microgravity). Five standing adult subjects had their feet attached to a platform, their eyes were open, and their hands were clasped behind their back. They were instructed to bend the trunk (the head and the trunk together) forward by approximately 35 degrees with respect to the vertical in the sagittal plane as fast as possible in response to a tone, and then to hold the final position for 3 s. The initial and final anteroposterior center of mass (CM) positions (i.e., 200 ms before the onset of the movement and 400 ms after the offset of the movement, respectively), the time course of the anteroposterior CM shift during the movement, and the electromyographic (EMG) pattern of the main muscles involved in the movement were studied under both normo- and microgravity. The kinematic synergy was quantified by performing a principal components analysis on the hip, knee, and ankle angle changes occurring during the movement. The results indicate that 1) the anteroposterior position of the CM remains minimized during performance of forward trunk movement in microgravity, in spite of the absence of equilibrium constraints; 2) the strong joint coupling between hip, knee, and ankle, which characterizes the kinematic synergy in normogravity and which is responsible for the minimization of the CM shift during movement, is preserved in microgravity. It represents an invariant parameter controlled by the CNS. 3) The EMG pattern underlying the kinematic synergy is deeply reorganized. This is in contrast with the invariance of the kinematic synergy. It is concluded that during short-term microgravity episodes, the kinematic synergy that minimizes the anteroposterior CM shift is surprisingly preserved due to fast adaptation of the muscle forces to the new constraint.

Kinematic synergies and equilibrium control during trunk movement under loaded and unloaded conditions.

The aim of the present investigation was to study the adaptation of the kinematic synergy responsible for equilibrium control during upper trunk movements to a 10-kg load added to the subject's shoulders. Five adult subjects were asked to bend their upper trunk forward to an angle of 35 degrees and then to hold the final position for 3 s, first without any load and then with a 10-kg load fixed to their shoulders. The final anteroposterior CM positions 400 ms after the movement offset, the time course of the anteroposterior center of mass (CM) shift during the movement, the EMG pattern of the main muscles involved in the movement and the initial CP shift were studied under both unloaded and loaded conditions. The kinematic synergy was quantified by performing a principal components analysis on the hip, knee and ankle angle changes occurring during the movement. The results indicate that: (1) the final anteroposterior position of the CM changed little if at all in the presence of the additional load, and that the anteroposterior CM shift was minimized throughout the duration of the movement; (2) the kinematic synergy was still characterized, in the presence of the additional load, by a strong coupling between the angle changes, as indicated by the fact that the first principal component (PC1) accounted for more than 99% of the hip, knee and ankle joint movements. A change was observed, however, in the ratio between the angles: the ankle extension increased, thus compensating for the additional theoretical forward CM shift that the additional load could be expected to cause; (3) the lack of change in the initial backward CP shift observed under loaded condition as well as the lack of change of the initial agonist EMG bursts suggest that the initial feedforward control of the kinematic synergy was not affected in the presence of the additional load. An increase in the antagonist bursts, presumably reflecting an adaptation of the kinematic synergy, was observed during the late phase of the movement; and (4) it is concluded that the adaptation of the kinematic synergy to the load was due to a specific change in the feedback control during the braking phase of the movement which presumably increases the ankle joint extension and consequently causes an increased backward shift of the hip which compensates for the forward shift due to the load.

Arm raising in humans under loaded vs. unloaded and bipedal vs. unipedal conditions.

The aim of the present experiment was to study the central organization of equilibrium control during arm raising in the frontal plane. Nine adult subjects (five seniors and four young adults) were asked to raise their right arm to a horizontal position in the frontal plane in two support conditions (bipedal vs. unipedal) and two load conditions (unloaded vs. a 3.5-kg load added on the moving hand). No instructions were given concerning the movement speed. The movements were performed at about half the maximum speed achievable under reaction time conditions. The final lateral center of mass (CM) position 1 s after the movement offset, and the time course of the CM shift during the movement were studied in the four experimental conditions, using a CM compensation index. The electromyographic (EMG) pattern of the main muscles involved in the movement performance and in the postural control were studied in three out of nine subjects during movements performed at two velocities (at the preferred speed and as fast as possible). The results indicate that (1) the CM shift remains minimized in the frontal plane during the time course of the arm movement and during the final stabilization of the arm regardless of the stance and load conditions; (2) the time course of the CM compensation index remains stable during the first 400 ms after the movement onset, decreasing late in the movement and increasing again at the end of the stabilization stage. A modelisation suggests that the time course is the result of the interaction of two controls: a first one, putative feedforward, starting early and decreasing with time and a second one, putative feedback, starting late in the movement and increasing with time; (3) both early and late index values are influenced by the support and load conditions, the highest index values being observed during unipedal stance and load conditions; (4) activation of quadratus lomborum (QL) contralateral to the raising arm is time locked with the deltoidus activation of the raising arm in both fast and slow movements: this contralateral QL activation corresponds to an anticipatory postural adjustment (APA) aimed at minimizing the CM shift.