The neuronal group selection theory: promising principles for understanding and treating developmental motor disorders.
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Brain↗
Biomedical subjects
M Hadders-Algra
Publications and source records attributed to M Hadders-Algra.
Shared memory representations for programming of lifting movements and associated whole body postural adjustments in humans.
This study examined whether the same memory representation is used for the parametric control of precision lifting and associated postural adjustments (APAs). Fifteen adults lifted object of different weights between the thumb and index finger. The employed grip, load (vertical lifting) forces, and ground reaction forces were recorded and the centre of pressure (COP) displacement as well as the corresponding first time derivatives were calculated. A highly significant correlation was found between the maximum rates of the load force, grip force and COP displacement rate. Different loads also influenced the onset of the COP displacement. The results corroborate the idea that the same memory representations which are used to control the manipulative lifting movement also control the APAs.
Adult↗
The development of postural adjustments during reaching in 6- to 18-month-old infants. Evidence for two transitions.
The present study focused on the developmental changes of postural adjustments accompanying reaching movements in healthy infants. We made a longitudinal study of ten infants between 6 and 18 months of age. During each session multiple surface electromyograms of arm, neck, trunk and leg muscles at the right side of the body were recorded during right-handed reaching movements in two positions ("upright sitting" in an infant chair and "long-leg" sitting without support). Simultaneously the whole session was recorded on video. Comparable data were present from the same infants at 3-5 months. Additionally, 18 infants (8-15 months) were assessed once during similar reaching tasks, but in these infants electromyographic activity of the trunk and neck muscles at both sides of the body were recorded. Our data revealed two transitions in the development of postural adjustments. The first transition was present around 6 months of age. At this age the postural muscles were infrequently activated during reaching movements. At 8 months ample postural activity reappeared and the infants developed the ability to adapt the postural adjustments to task-specific constraints such as arm movement velocity or the sitting position at the onset of the reaching movement. The second transition occurred between 12 and 15 months. Before 15 months the infants did not show consistent anticipatory postural activity, but from 15 months onwards they did, particularly in the neck muscles.
Arm↗
Postural adjustments during spontaneous and goal-directed arm movements in the first half year of life.
We studied the development of postural control during goal-directed reaching and spontaneous arm movements in early infancy. Two groups of infants participated. The first group consisted of 10 healthy infants, who were assessed four times at the ages of 3, 4, 5 and 6 months. Each assessment consisted of simultaneous recording of video-data and surface EMGs of arm, neck, trunk, and leg muscles in various lying and sitting positions. Additionally, postural adjustments during spontaneous arm movements were studied in a second group of five infants aged 1-3 months. Already before the onset of successful reaching, which occurred at 4 5 months, both spontaneous and goal-directed arm movements were accompanied by a high amount of postural activity. During the goal-directed arm movements a preference for neck muscle activation and a direction specific organisation (dorsal postural muscles activated before the ventral antagonists) prevailed, whereas during spontaneous arm movements such a specific postural organisation was absent. With increasing age and concurrent with successful reaching, the amount of postural activity decreased. Still, the persisting postural activity continued to become more organised with increasing age. Position affected the postural adjustments accompanying goal-directed arm movements at all ages.
Arm↗
Quality of general movements in infancy is related to neurological dysfunction, ADHD, and aggressive behaviour.
The quality of general movements (GMs) was assessed repeatedly during the first postnatal months in a mixed group of 52 children at either low or high risk for neurodevelopmental disorders. In addition, all children were reexamined at 4 to 9 years. The follow-up assessment consisted of a neurological examination and an evaluation of behaviour by means of parental questionnaires. The quality of GMs changed frequently, to stabilize in the final phase. The final GM phase is that of the so-called fidgety GMs which occurs between 2 and 4 months postterm. The quality of the fidgety GMs predicted outcome very well. Definitely abnormal GMs were associated with a high risk for the development of cerebral palsy, whereas mildly abnormal GMs were associated with the development of minor neurological dysfunction, attention-deficit-hyperactivity disorder, and aggressive behaviour.
Aggression↗
Development of postural adjustments during reaching in infants with CP.
The development of postural adjustments during reaching movements was longitudinally studied in seven infants with cerebral palsy (CP) between 4 and 18 months of age. Five infants developed spastic hemiplegia, one spastic tetraplegia, and one spastic tetraplegia with athetosis. Each assessment consisted of a simultaneous recording of video data and surface EMGs of arm, neck, trunk, and leg muscles during reaching in various lying and sitting positions. The basic organization of postural adjustments of the children developing spastic CP was intact. Their main problem was a deficient capacity to modulate the postural adjustments to task-specific constraints - a deficit which was attributed to a combination of an impaired motor coordination and deficits in sensory integration. The child with spastic-dyskinetic CP showed distinct abnormalities in the basic organization of postural adjustments.
Cerebral Palsy↗
Periventricular leucomalacia and preterm birth have different detrimental effects on postural adjustments.
Postural adjustments during sitting on a moveable platform were assessed by means of multiple surface EMGs of neck, trunk and leg muscles and kinematics in three groups of children, aged 1 1/2-4 1/2 years. The first group consisted of 13 preterm children (born at a gestational age of 25-34 weeks), whose neonatal ultrasounds had shown distinct lesions of the periventicular white matter (PWM). The second group was the preterm control group, consisting of 13 preterm children with normal neonatal brain scans, matched to the PWM group with respect to gestational age at birth, birth weight, sex and age of postural assessment. The third group was formed by 13 healthy children born at term and matched to the PWM group with respect to sex and age at examination. In addition to the postural assessment an age-specific neurological examination was carried out. Three of the children of the PWM group developed a cerebral palsy syndrome, nine showed minor neurological dysfunction and one child was neurologically normal. In the preterm control group one child showed minor neurological dysfunction, while the remaining 12 children of this group and all children of the full-term group were neurologically normal. The postural assessment revealed that preterm birth was associated with two types of postural dysfunction. One dysfunction was related to the presence of a PWM lesion and consisted of a limited repertoire of response variation. The other dysfunction was not related to the presence of a PWM lesion, but to preterm birth itself. It consisted of a change in the ability to modulate the postural responses. Preterm children showed a higher sensitivity to platform velocity than full-term children, and they lacked the capacity to modulate EMG amplitude with respect to initial sitting position.
Biomechanical Phenomena↗
Development of postural adjustments during reaching in preterm infants.
Preterm infants often show postural abnormalities, such as hyperextension of neck and trunk, which can interfere with motor and cognitive development. Little is, however, known on the pathophysiology of postural development in preterm infants. Therefore, we longitudinally studied the development of postural adjustments during reaching movements in 12 preterm infants between the (corrected) ages of 4 and 18 mo. Five infants showed minor neurological dysfunctions at 18 mo, such as a mild diffuse hypotonia, a mild hypertonia of the legs, or a mild asymmetry in posture and motility, and seven infants were neurologically normal. Each assessment consisted of a simultaneous recording of video-data and surface electromyograms of arm, neck, trunk, and leg muscles during reaching in various lying and sitting positions. Comparable data on postural development in ten full-term infants were available. The preterm infants showed an excessive amount of postural activity during reaching movements at all ages studied. Moreover, the postural adjustments were temporally disorganized and could not be modulated with respect to the velocity of the arm movement and the initial sitting position. We hypothesized that the preterms' disability to modulate their postural adjustments might be due to a reduced capacity to learn from prior experience. In our small group the postural dysfunctions were not related to the presence of hyperextension at early ages, to the neurological outcome at 18 mo, or to the lesions found on the neonatal brain ultrasound scans.
Birth Weight↗
Proprioceptive control of posture: a review of new concepts.
The assumption that proprioceptive inputs from the lower legs are used to trigger balance and gait movements is questioned in this review (an outgrowth of discussions initiated during the Neural Control of Movement Satellite meeting held in Cozumel, Mexico, April 1997). Recent findings presented here suggest that trunk or hip inputs may be more important in triggering human balance corrections and that proprioceptive input from the lower legs mainly helps with the final shaping and intermuscular coordination of postural and gait movements. Three major questions were considered. First, what role, if any, do lower-leg proprioceptive inputs play in the triggering of normal balance corrections? If this role is negligible, which alternative proprioceptive inputs then trigger balance corrections? Second, what is the effect of proprioceptive loss on the triggering of postural and gait movements? Third, how does proprioceptive loss affect the output of central pattern generators in providing the final shaping of postural movements? The authors conclude that postural and gait movements are centrally organized at two levels. The first level involves the generation of the basic directional-specific response pattern based primarily on hip or trunk proprioceptive input secondarily on vestibular inputs. This pattern specifies the spatial characteristics of muscle activation, that is which muscles are primarily activated, as well as intermuscular timing, that is, the sequence in which muscles are activated. The second level is involved in the shaping of centrally set activation patterns on the basis of multisensorial afferent input (including proprioceptive input from all body segments and vestibular sensors) in order that movements can adapt to different task conditions. Copyright 1998 Elsevier Science B.V.
Journal Article↗
Postural adjustments accompanying fast pointing movements in standing, sitting and lying adults.
The present study evaluated the effect of different positions, which varied in the amount of bodily support, on postural control during fast pointing movements. Fourteen adult subjects were studied in standing, various sitting and lying positions. Multiple surface electromyograms (EMGs) of arm, neck, trunk and upper leg muscles and kinematics were recorded during a standard series of unilateral arm movements. Two additional series, consisting of bilateral arm movements and unilateral arm movements with an additional weight, were performed to assess whether additional task-load affected postural adjustments differently in a sitting and standing position. Two pointing strategies were used--despite identical instructions. Seven subjects showed an elbow extension throughout the movements. They used the deltoid (DE) as the prime mover (DE group). The other seven subjects performed the movement with a slight elbow flexion and used the biceps brachii (BB) as the prime mover (BB group). The two strategies had a differential effect on the postural adjustments: postural activity was less and substantially later in the BB-group than in the DE group. Anticipatory postural muscle activity was only present in the DE group during stance. In all positions and task-load conditions the dorsal postural muscles were activated before their ventral antagonists. The activation rate, the timing and--to a lesser extent the amplitude of the dorsal muscle activity was position dependent. The position dependency was mainly found in the caudally located lumbar extensor (LE) and hamstrings (HAM) muscles. The EMG amplitude of LE and HAM was also affected by body geometry (trunk and pelvis position). Position and body geometry had only a minor effect on the activity of the neck and thoracic extensor muscles. This difference in behaviour of lower and upper postural muscles suggests that they could serve different postural tasks: the lower muscles being more involved in keeping the centre of mass within the limits of the support surface, and the upper ones in counteracting the reaction forces generated by movement onset. Increasing task-load by performing bilateral movements and--to a minor extent--during loaded unilateral movements affected the temporal and quantitative characteristics of the postural adjustments during standing and sitting in a similar way. The effect was present mainly during the early part of the response (within 100 ms after prime mover onset). This suggests that feedforward or anticipatory mechanisms play a major role in the task-specific modulation of postural adjustments.
Adaptation, Physiological↗
Qualitative assessment of general movements in high-risk preterm infants with chronic lung disease requiring dexamethasone therapy.
OBJECTIVE: The objective of this study was to determine in preterm infants at risk for severe chronic lung disease (1) the quality of general movements (GMs) and (2) the effect of dexamethasone treatment on spontaneous motor activity. STUDY DESIGN: In 15 very low birth weight infants the quality of GMs was assessed from repeated videotape recordings. Recordings were made at weekly intervals during the preterm period until term age and thereafter three times until the twentieth postterm week. All infants required dexamethasone therapy, and additional recordings were made a few hours before and 24 hours, 48 hours, and 7 days after dexamethasone was started. The relationship among movement quality, brain ultrasonographic abnormalities, and long-term outcome was explored. Acute effects of dexamethasone on motor activity were examined. RESULTS: After dexamethasone therapy was started, a significant transient reduction of the quantity of most spontaneous movements (p < 0.05) and a reduction of speed and amplitude of GMs was found (p < 0.05). A significant relationship was found between the severity of brain ultrasonographic abnormalities and the extent to which developmental trajectories of GMs were abnormal (p < 0.001). The development of cerebral palsy was related to the presence of cramped-synchronized movements near term (p < 0.02) and to the absence of fidgety movements at the age of 3 months after term (p < 0.05). CONCLUSION: In preterm infants with severe chronic lung disease and brain lesions, dexamethasone treatment leads to an acute reduction in motility and changes in the speed and amplitude of GMs. Until more is known about long-term neurologic sequelae, a cautious use of systemic dexamethasone therapy in preterm infants is recommended.
Chronic Disease↗
Development of postural control--differences between ventral and dorsal muscles?
Postural control is organized in basic, direction specific synergies which can be adapted to task-related conditions. Studies on the development of postural adjustments in young sitting children revealed that largely variable, direction specific muscle activation patterns are already present in 5-6 month old children not able to sit without support. With increasing age, the variation in muscle activation patterns decreases, resulting in a selection of the most complete patterns of synergist activation at 9-10 months of age. The synergy of the dorsal extensor muscles (during a forward sway of the body) develops faster than the synergy of the ventral flexors (during backward body-sway). A 'fixed' extensor synergy is prominently present between 9 months and 3 years, i.e. during the period when standing and walking abilities develop. With increasing age the 'fixed' extensor synergy gradually dissolves. The flexor synergy shows a larger flexibility than the extensor synergy, a difference which can be attributed to differences in stability limits and differences in the degree of supraspinal modulation.
Humans↗
The development of postural response patterns during reaching in healthy infants.
Reaching movements in adults are accompanied by complex postural adjustments which are controlled by spatial, temporal, and quantitative parameters. The basic postural adjustments are selected on the basis of the spatial parameter, whereas fine tuning of the pattern is guided by temporal and quantitative parameters. In specific conditions, such as during fast arm movements, postural adjustments have an anticipatory character. Recently, the development of postural adjustments during reaching was studied longitudinally in infants aged 3-18 months, placed in supine and sitting positions. The data revealed that already at 4 months, the age at which successful reaching emerges, reaching movements are accompanied by complex postural adjustments. The early postural patterns resembled the adult ones in spatial features (dorso-ventral ordering), temporal characteristics (top-down recruitment), and position dependency. With increasing age the postural patterns changed considerably, including a transient period of less extensive postural activity at 6-8 months, the age at which rolling, sitting up and crawling develops. Postural anticipation during reaching was not consistently present at any age.
Adult↗
Postural control in sitting children with cerebral palsy.
Children with cerebral palsy (CP) display postural problems, largely interfering with daily life activities. Clarification of neural mechanisms controlling posture in these children could serve as a base for more successful intervention. Studies on postural adjustments following horizontal forward and backward displacements of a movable platform in ten school-age children with spastic diplegia and non-disabled controls revealed that sitting CP children, like standing CP children, show direction specific postural adjustments, indicating that the basic pattern of muscle coordination in these conditions is conserved. Dysfunctions are especially present in the modulation of the response pattern of ventral muscles during forward translations. They consist of: (1) a stereotyped and non-variable activation of all ventral muscles; (2) an abnormal top-down muscle recruitment; and (3) an excessive degree of antagonistic co-activation. The altered patterns of muscle coordination could be the result of two interacting mechanisms, the primary deficit due to the early brain damage and a compensation due to the postural instability. Especially the latter dysfunction furnishes opportunities for therapeutic help.
Cerebral Palsy↗
Development of macronutrient composition of very preterm human milk.
The effects of gestational age at delivery (GA), postnatal age (PNA) and post-menstrual age (PMA = PNA + GA, an indicator of autonomous developmental processes not affected by the moment of birth) on macronutrient composition of very preterm milk were studied. Total N, fat, lactose and carbohydrate concentrations, energy density and 24 h volume were determined in 282 24 h milk samples collected at weekly intervals (days 7-55 of lactation) from seventy-nine women delivering their babies between 25 and 29 weeks of gestation. GA related differences were found for carbohydrate concentration only: carbohydrate concentration was lower with increasing GA. PNA was related to a decrease in total N and an increase in lactose concentration. PMA was not related to milk composition. Our data indicate that PNA strongly influences the development of the composition of very preterm human milk, while GA affects carbohydrate content with a negligible effect on the nutritional value of the milk. We conclude that in accordance with current opinion in paediatrics, human milk is the best source of nutrients even for very preterm (< 30 weeks GA) infants.
Analysis of Variance↗
Do girls with minor neurological dysfunction mature at a later age?
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Adolescent↗
Postural adjustments during sitting at preschool age: presence of a transient toddling phase.
The present study investigated developmental changes in postural adjustments during preschool age. Postural responses during sitting on a moveable platform were assessed in 21 healthy children aged 1 1/2 to 4 1/2 years. Multiple surface EMGs of neck, trunk, and leg muscles were recorded during forward and backward translations. Comparable data were available for 11 infants seen three times between the ages of 5 and 10 months. The data revealed the existence of a transient period between the ages of 9 to 10 months and 2 1/2 to 3 years, during which perturbations in a sitting position are accompanied by high activity in the direction-specific agonist muscles and in the antagonist muscles. After this period, agonist activity became more variable, particularly so during backward translations, and antagonist activity disappeared. These changes could be attributed to biomechanical factors and to maturation of the nervous system.
Child Development↗
Development of postural control, a basic aspect of neuro-ontogeny.
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Animals↗