Goal-directed arm movements in children with fetal alcohol syndrome: a kinematic approach.

BACKGROUND: Although many studies have documented deficits in general motor functioning in children with fetal alcohol syndrome (FAS), few have employed detailed measurements to explore the specific nature of such disabilities. This pilot study explores whether three-dimensional (3D) kinematic analysis may generate increased knowledge of the effect of intrauterine alcohol exposure on motor control processes by detecting atypical upper-limb movement pattern specificity in children with FAS relative to typically developing (TD) children. METHODS: Left and right arm and head movements during a sequential unimanual goal-directed precision task in a sample of children with FAS and in TD children were registered by an optoelectronic tracking system (ProReflex, Qualisys Inc.). RESULTS: Children with FAS demonstrated evidently poorer task performance compared with TD children. Additionally, analyses of arm movement kinematics revealed atypical spatio-temporal organization in the children with FAS. In general, they exhibited longer arm movement trajectories at both the proximal and distal level, faster velocities at the proximal level but slower at the distal level, and more segmented distal movements. Children with FAS also showed atypically augmented and fast head movements during the task performance. CONCLUSIONS: Findings indicate neuromotor deficits and developmental delay in goal-directed arm movements because of prenatal alcohol exposure. It is suggested that 3D kinematic analysis is a valid technique for furthering the understanding of motor control processes in children with FAS/fetal alcohol spectrum disorders. A combination with relevant neuroimaging techniques in future studies would enable a more clear-cut interpretation of how atypical movement patterns relate to underlying brain abnormalities.

Vision of the hand and environmental context in human prehension.

Previous findings on the role of visual contact with the hand in the control of reaching and grasping have been contradictory. Some studies have shown that such contact is largely irrelevant, while more recent ones have emphasised its importance. In contrast, information arising from the surrounding environment has received relatively little attention in the study of prehensile actions. In order to identify the roles of both sources of information, we made kinematic comparisons between three conditions. In the first, reaching was performed in a dimly lit room and compared with a second condition in which reaches in the dark, but with the thumb and first finger illuminated, were made to a luminous object. This contrast allows the effects of environmental context to be identified. A comparison between the second and a third condition, in which both vision of the hand and the environment was removed, but the object was still visually available, enabled the assessment of how and when vision of the hand plays a role. Removing environmental cues had effects both early and late in the reach, while vision of the hand was only crucial in the period after peak deceleration. In addition, removal of both sources of information resulted in larger grip apertures. Differences and similarities between our findings and those of other studies are discussed, as is the ongoing debate about the relative importance of visual feedback of the hand in the control and co-ordination of prehensile actions. We conclude with suggestions for further research based on the set-up used in the present study.

Motor asymmetries in the human newborn are state dependent, but independent of position in space.

Human newborns have a preference for turning and maintaining the head to one side of the body. Most studies confirm a right-sided preference in supine. Few have addressed the state dependency of this lateral bias, and even fewer have examined whether it is also expressed in the semi-upright position. We investigated whether it varies as a function of behavioural state and position in space. Kinematic recordings of head movements were made with the newborn secured on a platform in the supine or semi-upright position, which alleviated biomechanical and postural constraints imposed by gravity. Newborns differed as to whether they had a vertex, Caesarean or breech delivery. The majority of infants maintained a right-sided preference in both positions, but it was strongly mediated by state. Delivery type did not account for any lateral bias. These findings provide convincing evidence that a lateral bias in movement and positioning of the head are reflections of active neural processes rooted in the regulation of state.

Lateral biases in head turning and the Moro response in the human newborn: are they both vestibular in origin?

Head turning after release from the midline and the Moro response to a full-body drop in 15 full-term newborns lying supine on a custom-built platform was studied. While the lateral bias for head turning was not as pronounced as for the Moro response, it was still assumed in the ratio of 2 (right):1 (left) as predicted by Previc (1991). Onset latency and time-to-peak acceleration were both significantly shorter in the right arm during the initial phase of the Moro response. For both measures, this right arm bias persisted over four consecutive elicitations in most infants. Vaginally delivered infants and those born by Caesarean section did not differ in terms of head preference and the two measures of arm advantage. Our main finding was that infants with a right-sided head preference had a consistently shorter onset latency for the right arm. We interpret this association as stemming from a common labyrinthine asymmetry that involves different vestibulospinal pathways for the neck and arm muscles. In general, our findings are discussed in the context of Previc's (1991) left-otolithic dominance hypothesis and Grattan, De Vos, Levy, and McClintock's (1992) model of newborn functional asymmetries.

Head position preference in the human newborn: a new look.

Head position preference was studied in 20 awake newborns who differed in terms of delivery and sex. They were placed supine on a custom-built platform to reduce the effects of gravity and asymmetries in trunk posture and skull shape. A global and a specific scoring method were used, the infants being in State 3 (quiet wakefulness) or 4 (active wakefulness, excluding crying). Delivery and sex did not account for differences in head position. The head turned more often to the right and was maintained longer in this position during State 3, regardless of scoring method. The maintenance of the head in midline was comparable in duration to that reported for infants at 2-3 months when using the global scoring method. This suggests that the neural mechanisms responsible for attaining and maintaining a midline position are present at birth, but are not functionally expressed due to a lack of adequate power in the antigravity muscles of the neck.

A critical examination of the Moro response in newborn infants--symmetry, state relation, underlying mechanisms.

The primary purpose of the present study was to analyze quantitatively the vestibular evoked Moro response, and the symmetry of the movement pattern involved, as the traditional descriptions bring about. Another aim was to determine the segmental movements involved and determine whether the components of the Moro response are dependent on changes in the infant's behavioral state. Another question concerns whether the form of these movements changed over repeated trials on the same day, or from the first to the fifth day after birth. Vestibular evoked Moro responses of 52 neonates, 1-5 days of age, elicited in different behavior states (State 1-5), were examined and quantitatively analyzed. The response was evoked by a predefined, rapid, downward, vertical body motion, without any dorsiflexion of the infant's head. Optoelectronic device (SELSPOT II) were used to monitor the arm/hand movement patterns involved in the response. The three-dimensional movement pattern in space, duration, velocity, latency, and the acceleration of both arms/hands were analyzed in relation to the infant's behavioral state. The response movements were structured into phases of abduction/extension, adduction/flexion and the extension/flexion of the fingers. The vestibular stimulation used was found to be sufficient for eliciting an adequate Moro response. The segmental movement pattern of the Moro response was found to be sensitive to the infant's behavioral state at the time when the response was elicited. This was found in the movement pattern, duration, latency, and the velocity of the response. The response was found to be asymmetrical, in 82% of the infants it was found to be a predominant shorter onset latency of the right arm, in 12% the opposite was found. These findings suggest that there is a fundamental, spinal asymmetry involved in the Moro response which is subject to supraspinal influences emanating from the vestibulospinal system. No differences were found between 1 and 5 days of age for any of the scoring categories, and no differences were found within groups over six successive trials.

The structuring of neonatal arm movements.

The organization and structuring of spontaneous arm movements of 8 neonates were studied quantitatively. The movements were divided up into units, each consisting of 1 acceleration and 1 deceleration phase. This analysis showed that the movements had a distinct temporal structuring. An analysis of curvature was also performed, and it showed that the most distinct changes in movement direction occurred at the transitions between movement units. Finally, the movements of the 2 arms were found to be coupled in all 3 dimensions of space. They had a clear tendency to move together along the body's longitudinal axis, abduct and adduct together, and extend together in the forward direction.

Preparation for grasping an object: a developmental study.

The development of visually controlled grasping actions was studied in two experiments. An optoelectronic technique (SELSPOT) was used to monitor the opening and closing of the hand during reaching actions by measuring the change in the distance between thumb and index finger. The purpose of Experiment 1 was to establish an adult criterion for the development. It was shown that adults started closing the hand around the target well before touch and that the timing was dependent on the size of the target. The hand started to close earlier when grasping a small rather than a large target. In addition, the degree of hand opening was also less for a small than for a large target. In Experiment 2 it was shown that infants who were 5-6, 9, and 13 months of age also controlled their grasping actions visually and started closing the hand around the target in anticipation of the encounter rather than as a reaction to the encounter. However, the strategy of the two younger age groups was different from that of adults. They started closing the hand closer to the time of contact with the target than did the 13-month-olds, who were comparable to adults in this respect. The timing was not dependent on the size of the target in any of the infant groups. In all age groups, reaching and grasping were most commonly organized in a continuous way; that is, the hand started to close without any interruption in the approach. The opening of the hand was found to be adjusted to target size in the 9- and 13-month-olds but not in the 5-6 month olds.