Biomedical subjects

H Forssberg

Publications and source records attributed to H Forssberg.

At least 55 records · Page 3Linked to original sources

PubMed1997

Psychomotor development at 10 months as related to neonatal health status: the Stockholm Neonatal Project.

The psychomotor development of 171 preterm very-low-birthweight (VLBW) infants (birthweight < or = 1500 g) at 10 months of corrected age was assessed by the Griffiths' Mental Developmental Scale. The developmental score was related to the prenatal and obstetric risk factors and to the neonatal health status of each infant. These results, in turn, were compared to findings for a reference group of full-term infants. This analysis revealed that prolonged ventilator treatment, patent ductus arteriosus, bronchopulmonary dysplasia, brain haemorrhage with ventricle dilatation, white matter lesions, low birthweight and low gestational age influenced psychomotor development in an unfavourable manner. Multiple regression analysis confirmed most of these correlations. Preterm birth per se (when children with risk factors were excluded) in general had no significant effect on psychomotor development. However, the early development of preterm infants with several neonatal risk factors was adversely affected.

Case-Control Studies↗

PubMed1997

Nature and nurture in the development of postural control in human infants.

Nowadays, the controversy on "nature" and "nurture" in motor development focuses on the development of automatic motor patterns. The present paper discusses this issue within the framework of a recent study on the effect of maturation and training on the development of postural adjustments in sitting infants. This study revealed that already before the age of sitting without help, highly variable but direction-specific muscle activation patterns are present. This suggests that postural adjustments develop via an innate repertoire of primary direction-specific response patterns. The following developmental step consists of a decrease in muscle activation patterns, which results in selection of the most complete patterns of synergist activation. In accordance with Edelman's neuronal group selection theory, pattern selection turned out to be experience dependent, as it appeared to be guided by cues on head stabilization and enhanced by daily balance training.

Child Development↗

PubMed1996

Ontogeny of postural adjustments during sitting in infancy: variation, selection and modulation.

1. The aim of the study was to find out whether the development of postural adjustments occurs via a coupling of simple muscle responses, such as stretch reflexes, or via selection from an innate repertoire of centrally generated response patterns. 2. Postural responses during sitting on a moveable platform were assessed in eleven healthy infants at 5-6, 7-8 and 9-10 months of age. Multiple surface EMGs and kinematics were recorded while the infants were exposed to slow and fast horizontal forward (Fw) and backward (Bw) displacements of the platform. 3. From the youngest testing age onwards, largely variable but direction-specific muscle activation patterns were present. Fw translations resulted predominantly in an activation of the neck flexor, the rectus abdominis and rectus femoris muscle, while the neck-, thoracal- and lumbar extensor muscles (NE, TE, LE) and the hamstrings (Ham) showed varying amounts of inhibition. During Bw translations NE, TE, LE and Ham were preferably activated. The muscle activity could not be explained by simple stretch reflex mechanisms, but is likely to reflect centrally generated motor activity maturing in a predetermined way. However, indications for a contribution of stretch reflex mechanisms were also present. 4. With increasing age the variation in muscle activation patterns decreased, resulting in a selection of the most complete patterns. The ability to modulate the amplitude of the selected, most complete patterns during Fw translations, with respect to platform velocity and initial pelvis position, emerged at 9-10 months.

Afferent Pathways↗

PubMed1996

Training affects the development of postural adjustments in sitting infants.

1. The present study addressed the question of whether daily balance training can affect the development of postural adjustments in sitting infants. 2. Postural responses during sitting on a moveable platform were assessed in twenty healthy infants at 5-6, 7-8 and 9-10 months of age. Multiple surface EMGs and kinematics were recorded while the infants were exposed to slow and fast horizontal forward (Fw) and backward (Bw) displacements of the platform. After the first session the parents of nine infants trained their child's sitting balance daily. 3. At the youngest age, when none of the infants could sit independently, the muscle activation patterns were direction specific and showed a large variation. This variation decreased with increasing age, resulting in selection of the most complete responses. Training facilitated response selection both during Fw and Bw translations. This suggests a training effect on the first level of the central pattern generator (CPG) model of postural control. 4. Training also affected the development of response modulation during Fw translations. It accelerated the development of: (1) the ability to modulate EMG amplitude with respect to platform velocity and initial sitting position, (2) antagonist activity and (3) a distal onset of the response. These findings point to a training effect on the second level of the CPG model of postural adjustments.

Age Factors↗

PubMed1996

Impaired sensory-motor integration during grasping in writer's cramp.

Six subjects with writer's cramp and six healthy control subjects were examined while lifting a small instrumented object with variable weight and friction using the precision grip. The isometric grip and load forces were sampled at 400 Hz and stored in a flexible laboratory computer system for later analysis. Quantitative measurement of vibration and temperature sensibility showed normal sensory perception in the writer's cramp subjects. They exhibited an impaired programming of the grip-lift force co-ordination, while the ability to generate unimodal force-rate trajectories and to characterize the pattern of the force output according to memory representations of weight and friction of the object were intact. The capacity to terminate quickly the programmed grip force in lifts erroneously programmed too high was impaired. Writer's cramp subjects also employed excessive grip force during the static phase of the lift, and some patients had a short grip force latency after sudden unpredicted load increases, indicating a disinhibited spinal reflex response. The results indicate an impaired capacity in writer's cramp subjects to integrate sensory information in the motor programming and force regulation during precision grip tasks, despite a normal sensibility.

Adult↗

PubMed1996

Early infant grasping involves radial fingers.

Halverson's hypothesis states that prehension gradually develops from ulnar to forefinger holding. This hypothesis was tested by measuring the grip force of individual fingers (digits II to V) in 36 healthy children from 2.5 to 7 months of age. The results dismissed Halverson's hypothesis, since it was shown that from an early age the index finger played a leading role in grasping, usually contacting and initiating the grasp prior to the other fingers and producing a stronger grip force.

Child Development↗

PubMed1996

Postural control in children with spastic diplegia: muscle activity during perturbations in sitting.

To clarify the neural mechanisms controlling equilibrium during sitting, and the implications for the optimal sitting position for children with CP, automatic postural adjustments after perturbations of the support surface during sitting were investigated in seven children with spastic diplegia and in seven age-matched controls. A sudden backward sway of the body evoked brisk responses in ¿ventral' muscles in both groups. However, the order of muscle recruitment, which in most non-disabled children was caudal, was reversed in the children with diplegia, whose first response was in the neck flexors. The children with diplegia also co-activated antagonistic neck and hip muscles. The authors concluded that although children with spastic diplegia may produce a basic muscle activation pattern (first level of the central pattern generator, CPG), they cannot adjust the pattern in response to external changes (second level of the CPG).

Cerebral Palsy↗

PubMed1996

Glial fibrillary acidic protein is increased in the cerebrospinal fluid of preterm infants with abnormal neurological findings.

Glial fibrillary acidic protein (GFAP) is the structural protein of the intermediate filament of astroglia. The aims of the present study were to examine GFAP in the cerebrospinal fluid (CSF) of preterm infants at different postmenstrual ages and to evaluate the potential of GFAP to predict abnormal neurodevelopmental outcome. GFAP increased in correlation with postmenstrual age in preterm infants (n = 17) and full-term infants (n = 9). The levels were five times higher in preterm infants (n = 10) with an abnormal neonatal course and/or an abnormal neurological outcome than in healthy preterm infants. The positive predictive value of a GFAP higher than the 98th percentile of normal infants was 69%, while a GFAP level below this limit invariable predicted a good outcome. Simultaneously analysed noradrenaline, hypoxanthine and glutamate did not differ between the groups. We conclude that CSF GFAP increases with maturity and that CSF GFAP appears to be a promising marker for perinatal brain damage.

Biomarkers↗

PubMed1995

Development of human precision grip. V. anticipatory and triggered grip actions during sudden loading.

When an object held by a precision gripis subjected to an abrupt vertical load perturbation, somatosensory input from the digits triggers an increase in grip force to restore an adequate safety margin, preventing frictional slips. In adults the response occurs after a latency of 60-80 ms. In the present study, children from 2 years old upward and adults grasped and lifted an object using a precision grip. Sudden, unpredicted increases in load force (tangential to the grip surfaces) were induced by the experimenter by dropping a small disc on to a receptacle attached to the object. The impact elicited a grip force response which in young children had a longer latency and a smaller amplitude than was seen in adults. The grip response latency gradually become shorter and its amplitude increased with increasing age, reaching adult values at 6-10 years. The muscle activity underlying the response could have several bursts. The adults showed one brisk response, appearing 40-50 ms after impact, in extrinsic and intrinsic hand muscles, while younger children also exhibited a short-latency burst, appearing about 20 ms after impact. It is suggested that the short-latency response was mediated via spinal pathways, and that these pathways are disengaged by supraspinal centers during development. In a predictable loading situation, when subjects dropped the disc themselves into the receptable using the contralateral hand, they changed strategy. Adults induced a well-timed anticipatory grip force increase prior to the impact that was scaled to the weight of the object. The youngest children did not time the force increase properly in relation to the impact. Yet, they could scale their anticipatory grip force increase with respect to the weight of the dropped disc. This suggests a well-developed capacity to use information about the weight of objects held by one hand to parameterize a programmed force output to the other hand.

Child↗

PubMed1995

Development of human precision grip. IV. Tactile adaptation of isometric finger forces to the frictional condition.

The adaptation of the grip forces to the frictional condition between the digits and an object relies on feedforward sensorimotor mechanisms that use tactile afferent input to intermittently update a sensorimotor memory that controls the force coordination, i.e., the ratio between grip force (normal to the grip surface) and load force (tangential to the grip surface). The present study addressed the development of these mechanisms. Eighty-nine children and 15 adults lifted an instrumented object with exchangeable grip surfaces measuring the grip and load forces. Particularly in trials with high friction (sandpaper), the youngest children used a high grip force to load force ratio. Although this large safety margin against slips indicated an immature capacity to adapt to the frictional condition, higher grip forces were produced for more slippery material (silk versus sandpaper). The safety margin decreased during the first 5 years of age, in parallel with a lower variability in the grip force and a better adaptation to the current frictional condition. The youngest children (18 months) could adapt the grip force to load force ratio to the frictional condition in a series of lifts when the same surface structure was presented in blocks of trials, but failed when the surface structure was unpredictably changed between subsequent lifts. The need for repetitive presentation suggests a poor capacity to form a sensorimotor memory representation of the friction or an immature capacity to control the employed ratio from this representation. The memory effects, reflected by the influences of the frictional condition in the previous trial, gradually increased with age. Older children required a few lifts and adults only one lift to update their force coordination to a new friction. Hence, the present finding suggests that young children use excessive grip force, a strategy to avoid frictional slips, to compensate for an immature tactile control of the precision grip.

Adolescent↗

PubMed1995

Tactile control of isometric fingertip forces during grasping in children with cerebral palsy.

Sensory mechanisms and sensorimotor integration have often been thought to be disturbed in children with cerebral palsy (CP). The authors investigated the influence of tactile information from the fingertips on the isometric force regulation during the lift of a small object with the precision grip in children with CP and controls. Children with CP were able to modify their grip force according to friction between the fingertips and the object and could use tactile information for anticipatory control of the force-scaling of the precision grip, but they seemed to need predictable conditions and successive lifts to build up memory representation of an object's friction.

Case-Control Studies↗

PubMed1995

Early [18F]FDG positron emission tomography in infants with hypoxic-ischaemic encephalopathy shows hypermetabolism during the postasphyctic period.

Six full-term infants suffering from perinatal asphyxia and with moderate or severe hypoxic-ischaemic encephalopathy were investigated by positron emission tomography (PET). Regional cerebral metabolic rates of glucose (rCMRgl) were determined using [2-18F]2-fluoro-2-deoxy-D-glucose ([18F]FDG) PET scans at a median age of 2.5 days (range 2-5 days). Localized increases in rCMRgl were visually observed in five infants. In a subgroup of three infants, absolute values of rCMRgl in different brain regions were calculated. In all cases the results of the PET studies were in good agreement with those of the neuroradiological, neurophysiological and clinical investigations. Information indicating pathophysiological events could be extracted earlier with PET than with conventional morphological imaging techniques. We conclude that [18F]FDG-PET scans performed in critically ill, asphyxiated infants very soon after birth provide valuable information for the prediction about neurological outcome.

Asphyxia Neonatorum↗

PubMed1994

Postural adjustments in sitting humans following external perturbations: muscle activity and kinematics.

There are several controversies concerning the organization and induction of postural adjustments in standing humans. Some investigators suggest the responses are triggered by somatosensory inputs (especially from the ankle in standing subjects), while others emphasize the vestibular input induced by head acceleration. We examined postural responses in sitting subjects in order to describe the muscle activation pattern during various perturbations and to test whether somatosensory or vestibular stimulation elicited the responses. The kinematics and EMG patterns in response to perturbations caused by movements of the support surface were studied in adults. The postural muscle activation following a backward sway was mainly the same, whether it was elicited by a forward translation or a legs-up rotation. This is remarkable, since, except for pelvis rotation, the movements of all body segments including the head differed in the two conditions. Furthermore, a second experiment showed that the direction of the initial head movement could be reversed with retainment of the same postural muscle activation pattern. The results suggest that somatosensory signals derived from the backward rotation of the pelvis, and not vestibular information from the head, trigger postural responses during sitting. There was a slight but consistent difference in the muscle activation pattern, whether the backward sway was elicited by a forward translation or legs-up rotation. The difference seemed to reflect the sensory information from head and other body parts (except the pelvis). This finding allowed us to speculate in a central pattern generator for postural adjustments containing two levels. At the first level, a simple format of the muscle activation would be generated; at the second level, the centrally generated pattern could be shaped and timed by interaction from the entire somatosensory, vestibular, and visual input.

Acceleration↗

PubMed1994

Epigenetic development of postural responses for sitting during infancy.

This study examined whether postural responses emerge in children in a predetermined way before independent sitting is achieved, and in what respect postural responses in infants differ from those in adults. Children just able to sit independently and children not yet able to sit were exposed to surface perturbations (translation and rotation) while body movement and electromyographic (EMG) responses were recorded. Perturbations causing a backward sway of the body (i.e., forward translation and legs-up rotation), elicited consistent patterns of muscle activity in ventral hip, trunk, and neck muscles in the independently sitting children. A high tonic EMG background activity in trunk and neck extensor muscles was inhibited at the onset of the ventral muscle activity. Kinematic analysis revealed that backward rotation of the pelvis was the first detectable body movement, while head movements (linear and angular displacement) were irregular and occurred later than the pelvis movement. Perturbations in the opposite direction, causing a forward sway, evoked variable responses in dorsal trunk and neck muscles, suggesting that the excitability level for postural responses was set according to the stability limits of the body. Children not yet able to sit without support were tested when the support around the waist, given by the experimenter's hands, was released prior to the onset of the platform perturbation. Postural responses were elicited in ventral muscles following a backward sway in all children and in about 60% of all trials. Often, only some of the ventral muscles were activated. No distinct responses were evoked during perturbations imposing a forward sway. These results suggest that (1) backward rotation of the pelvis triggers the postural adjustments in the independently sitting children; (2) a basic form of the postural adjustment develops in a predetermined manner before children practice independent sitting; and (3) the basic structure of ventral muscle activation pattern resembles that of adults, while the activation of the dorsal muscles (inhibition) differs in several aspects. These findings are in agreement with a recent model of central pattern generators for postural responses consisting of two operative levels. At the first level, which is triggered by backward rotation of the pelvis, the basic activation pattern is generated. At the second level, the pattern is shaped and fine-tuned by multisensory interactions from all activated sensory systems.(ABSTRACT TRUNCATED AT 400 WORDS)

Electromyography↗

PubMed1994

Formation and lateralization of internal representations underlying motor commands during precision grip.

The capability to store and retrieve weight-related information from a lift to scale the force output during a subsequent lift was examined in 10 healthy adults and 50 children (age 2-10 years), as well as a 22-year-old patient with corpus callosum agenesis. Subjects lifted a test object between the thumb and index finger while the isometric fingertip forces were measured. The results suggest that both healthy children and adults can transfer weight-related information between the right and left hand, although a lateralization was found. Also, the storage and retrieval of weight-related information appears to be a dynamic process dependent on both previous sensory information and knowledge of future movements. Late maturation of interhemispheric connections and asymmetric loss of some information during the transfer between hemispheres suggest a lateralization of the internal representation. The patient with a corpus callosum agenesis supported this hypothesis.

Adolescent↗

PubMed1993

Morbidity and mortality in 262 infants with birth weight below 1500 g born in Stockholm County 1988-1992.

The aim of this study was to examine the relationship between neonatal clinical conditions and the development of senso-motoric handicaps. Two hundred and sixty-two infants with a birth weight < 1500 g, born in or referred to the Karolinska/S:t Göran's Children Hospital from September 1988 to April 1992 were studied prospectively. The total survival was 83%. Preliminary results of the Griffiths' test of these infants showed an average cognitive ability of the same level as for full-terms except for those pre-term infants who had suffered from the combination of chronic lung disease and leukomalacia. The incidence of moderate to severe senso-motoric disability is up to the present time 5%.

Humans↗

PubMed1992

Development of human precision grip. II. Anticipatory control of isometric forces targeted for object's weight.

The development of anticipatory control during lifts with the precision grip was examined in 100 children aged 1 to 15 years and in 15 adults. The children were instructed to lift an instrumented test object by using the precision grip between the thumb and index finger. The employed grip force, load force (vertical lifting force), vertical position and their corresponding time derivatives (i.e., grip and load force rates and acceleration) were recorded. The weight of the object was varied between trials to access the influence of the object's weight in the previous trial on the isometric force output. Already by the second year, children began to use information pertaining to the object's weight in the previous lift, i.e., they began to use an anticipatory control strategy. This occurred concomitant to the development of mainly bell shaped force rate profiles (Forssberg et al. 1991). The succeeding development of a more mature anticipatory control was gradual and adult-like capacity was not reached until 8-11 years of age.

Adolescent↗

PubMed1992

Development of human precision grip. III. Integration of visual size cues during the programming of isometric forces.

Recent evidence has shown that visual and haptical size information can be used by adults to estimate the weight of the object, forming the basis of the force programming during precision grip (Gordon et al. 1991a, b,). The present study examined the development of the capacity to use visual size information. In the first experiment, 30 children (age 1-7 years) and 10 adults performed a series of lifts with two boxes presented in an unpredictable order. The boxes were equal in weight but unequal in size and were attached to an instrumented grip handle which measured the employed grip force, load force, position and their corresponding time derivatives. The isometric force development was not influenced by the box size before the age of 3. However, the children aged 3 years and older demonstrated greater visual influences on the force programming than adults. To determine more precisely when children began to use visual size information, a second experiment in which the size and weight covaried was performed on 15 children. Children still did not use the size information during the force programming until the later half of the third year. It is concluded that this ability, probably involving associative transformations between the size and weight of objects, emerges around one year after anticipatory control based on somatosensory information pertaining to the weight of the object.

Adolescent↗