Biomedical subjects

A L van der Meer

Publications and source records attributed to A L van der Meer.

8 recordsLinked to original sources

PubMed1999

Development of perception in action in healthy and at-risk children.

Devising effective assessment techniques and therapy for movement disorders in young children requires in-depth measures of the child's perceptuo-motor functioning. It is argued that the field of movement disorders can benefit from an ecological approach to perception and action, where perception subserves action and action influences perception. Three notions central to the ecological approach are described and illustrated with our recent research on infant and child perceptual and motor behaviour.

Cerebral Palsy↗

PubMed1997

Keeping the arm in the limelight: advanced visual control of arm movements in neonates.

To test whether newborn babies have voluntary control over their limbs, spontaneous arm-waving movements were measured in the dark while the baby lay supine with its head turned to one side. A narrow beam of light was shone over the baby's nose or chest in such a way that the arm the baby was facing was only visible when the hand encountered the, otherwise, invisible beam of light. The results showed the babies were capable of precisely controlling the position, velocity, and deceleration of their arms so as to keep the hand visible in the light. The findings indicate that newborns can purposely control their arm movements to meet external demands and that the development of visual control of arm movement is underway soon after birth.

Attention↗

PubMed1996

Lifting weights in neonates: developing visual control of reaching.

To test whether newborn babies take account of external forces in moving their limbs, spontaneous arm-waving movements were measured while the baby lay supine with its head turned to one side. Free-hanging weights, attached to each wrist by strings passing over pulleys, pulled on the arms in the direction of the toes. The results showed the babies applied compensatory forces to keep the hand they faced moving in the same region. In contrast, the (invisible) contra-lateral hand was pulled down by the weights. In a second experiment, where the arms were occluded, both arms were pulled down, suggesting that sight of the arm was necessary in compensating for the weight. In a third, conclusive experiment the babies viewed the arm they were not facing on a small video-monitor and this time the babies kept the visible contra-lateral hand up despite the weights. The results challenge the general view that spontaneous arm movements of neonates are purposeless and either reflexive or due to spontaneous patterned efference to the muscles. Instead, the findings suggest that in waving their arms, neonates are developing visual control of reaching.

Attention↗

PubMed1995

The functional significance of arm movements in neonates.

Arm movements made by newborn babies are usually dismissed as unintentional, purposeless, or reflexive. Spontaneous arm-waving movements were recorded while newborns lay supine facing to one side. They were allowed to see only the arm they were facing, only the opposite arm on a video monitor, or neither arm. Small forces pulled on their wrists in the direction of the toes. The babies opposed the perturbing force so as to keep an arm up and moving normally, but only when they could see the arm, either directly or on the video monitor. The findings indicate that newborns can purposely control their arm movements in the face of external forces and that development of visual control of arm movement is underway soon after birth.

Arm↗

PubMed1995

Development of prospective control of catching moving objects in preterm at-risk infants.

Healthy term infants and infants classified as neurologically at-risk because of low birthweight and preterm birth were tested longitudinally between 20 and 48 weeks on the ability to use visual information predictively. Reaching for an object moving at different speeds was assessed; the object was occluded from view by a screen during the last part of its approach. At each infant's first reaching session, gaze anticipated the reappearance of the moving toy; however, onset of reaching and prospective control of gaze and hand varied considerably between the normal and at-risk groups. In addition, some at-risk infants geared their actions not to the time but to the distance that the toy was from the catching place, causing problems with faster-moving toys. The two children who anticipated least well were the only two of the at-risk group who were later diagnosed as having cerebral palsy.

Case-Control Studies↗

PubMed1994

Prospective control in catching by infants.

Catching a moving object requires the ability to predict the future trajectory of the object. To test whether infants can use visual information predictively, reaching for a toy moving at different speeds was investigated in six infants around 11 months of age. The toy was occluded from view by a screen during the last part of its approach. Gaze arrived at the exit side of the screen and the hand started to move forward before the toy had disappeared behind the occluder; these actions were prospectively geared to certain times before the toy would reappear. In addition, hand-movement duration was found to be related to the time of reappearance of the toy--the information used to regulate duration of hand movement being picked up before the toy disappeared behind the occluder. In a longitudinal experiment, the development of predictive reaching was investigated in two infants between the ages of 20 and 48 weeks. At all ages studied, gaze anticipated the reappearance of the moving toy. However, anticipation with hand movement of the disappearance of the toy and the ability to gear actions prospectively to the time (instead of distance) the toy was away from certain points on the track developed relatively late and marked the transition to successfully catching faster-moving toys.

Acceleration↗

PubMed1993

Optimizing antimicrobial prophylaxis in reconstructive vascular surgery.

The combinations of cefuroxime and metronidazole, and amoxycillin/clavulanate (Augmentin) are useful as prophylactic drugs during vascular surgery. In this study the pharmacokinetic profiles of different dosing regimens utilizing these drugs during reconstructive vascular procedures are presented. Three groups of patients, undergoing aortobifemoral or femoropopliteal prosthetic surgery, received one of the following regimens: Group I: 1500 mg metronidazole plus 1500 mg cefuroxime at premedication, Group II: 1500 mg metronidazole at premedication plus 1500 mg cefuroxime at the time of induction anaesthesia, followed by 750 mg of cefuroxime 2 h later, Group III: 2000 mg amoxycillin/200 mg clavulanate at time of induction anaesthesia, followed by 1000 mg amoxycillin/200 mg clavulanate, 3 h later. For determination of the antibiotic concentrations, arterial blood samples were obtained at 30-minute intervals during the entire procedure. An additional sample was collected at the time of inguinal graft site anastomosis. Cefuroxime concentrations in these additional samples were 29.3 +/- 11.2 mg/l in group I and 44.7 +/- 15.9 mg/l in group II. Metronidazole concentrations were satisfactorily high in all patients (38.4 +/- 4.5 mg/l). Amoxycillin/clavulanate concentrations were 35.1 +/- 21.5 mg/l and 4.4 +/- 3.7 mg/l respectively. We recommend a multiple dose administration scheme for prophylaxis in high-risk prosthetic vascular surgery, if the procedure takes more than 2-3 h and antimicrobial agents with a rapid elimination time are used. A multiple dosing scheme ensures sufficiently high antibiotic concentrations, exceeding the MIC of staphylococci and enterobacteria approximately twice, at the time of inguinal graft site anastomosis.

Aged↗

PubMed1991

Effect of task on movement control in cerebral palsy: implications for assessment and therapy.

In order to examine the possibility that children with cerebral palsy (CP) find abstract tasks, such as extending the arm as much as possible, more difficult than concrete tasks, such as reaching to grasp an object, nine hemiparetic children with CP and 12 nursery-school children were tested with both a concrete and an abstract task. The children with CP achieved a significantly larger range of movement in the concrete task, whereas the nursery-school children showed no difference between tasks. Thus the CP children's poorer performance on the abstract task did not fully reflect their movement capability. This means that conventional neurological measurements of limb function in cerebral palsy, which mainly use abstract tasks or passive movements, will give an incomplete picture of the child's action capability.

Cerebral Palsy↗