Michael Illert

Gait analysis during treadmill and overground locomotion in children and adults

Gait analysis on the treadmill and in the overground condition is used both in scientific approaches for investigating the neuronal organisation and ontogenetic development of locomotion and in a variety of clinical applications. We investigated the differences between overground and treadmill locomotion (at identical gait velocity) in 12 adults and 14 children (6-7 years old). During treadmill locomotion the step frequency increased by 7% in adults and 10% in children compared to overground walking, whereas the stride length and the stance phase of the walking cycle decreased. The swing phase, however, increased significantly by 5% in adults and remained unchanged in children. Balance-related gait parameters such as the step width and foot rotation angles increased during treadmill locomotion. The reduction of the step length was found to be stable after 10 min of treadmill walking in most subjects. With regard to the shifted phases of the walking cycle and the changed balance related gait parameters in the treadmill condition, we assume a different modulation of the central pattern generator in treadmill walking, due to a changed afferent input. Regarding the pronounced differences between overground and treadmill walking in children, it is discussed whether the systems generating and integrating different modulations of locomotion into a stable movement pattern have reached full capacity in 6-7 year old children.

Development of prehension movements in children: a kinematic study

Abstract To evaluate the normal development of functional hand motor skill, the kinematics of prehension movements were analyzed in 54 healthy children (age 4–12 years). The subjects repeatedly reached out for cylindrical target objects and grasped them with a precision grip of their dominant hand. The trajectory of the reaching hand and the finger aperture were monitored by optoelectronic motion analysis. To obtain comparable conditions for the different age groups, the experimental setup was scaled according to the individual body proportions of each subject. Within the investigated age range, neither the movement duration nor the normalized (according to body proportions) peak spatial velocity of the reaching hand changed significantly. However, the hand trajectory straightened and the coordination between hand transport and grip formation improved, resulting in smooth and stereotyped kinematic profiles at the age of 12 years. The younger children opened their grip relatively wider than the older ones, thus grasping with a higher safety margin. The dependence on visual control of the movement declined during motor development. Only the oldest childen were able to scale the grip aperture adequately, according to various sizes of the target objects, when visual control of the movement was lacking. The results suggest that the development of prehensile skills during childhood lasts until the end of the first decade of life. This functional maturation is discussed in relation to the development of neuronal pathways.

Absence of recurrent axon collaterals in motoneurones to the extrinsic digit extensor muscles of the cat forelimb

Forelimb alpha-motoneurones were intracellularly recorded in anaesthetized cats and iontophoretically filled with horseradish peroxidase (HRP). All motoneurones to the elbow flexors, elbow extensor and to the extensor carpi radialis muscles displayed in parallel homonymous recurrent inhibitory postsynaptic potentials (RIPSPs) and axon collaterals. Homonymous RIPSPs and axon collaterals were missing in the nuclei to the long digit extensor muscles. Two populations of motoneurones, with and without recurrent axon collaterals, seem to be present in the extensor carpi ulnaris motor nucleus. These results are consistent with the hypothesis that the motoneurones to the extrinsic digit extensors lack a recurrent axonal system. This indicates that the contribution of the recurrent Renshaw systems to motor control may be more complex than hitherto assumed.

Recurrent inhibition in the cat distal forelimb

The pattern of recurrent pathways from motor axon collaterals to motoneurones has been investigated in the spinal cord of anaesthetized cats with intracellular techniques. Only recurrent inhibitory postsynaptic potentials (RIPSPs) were observed so far. They were very pronounced between the mechanical synergists acting at the elbow. The triceps muscles received substantial effects also from the extensor carpi ulnaris (ECU) and from palmar-located medialis (M) and ulnaris (Ul) muscles. The effects were much smaller in the motor nuclei acting on the wrist (ECU, EC radialis (ECR]. The motor nuclei to the muscles acting on the phalanges (extensor digitorum communis and lateralis, extensor indicis proprius, and abductor pollicis longus (EDC, EDL, EIP, APL] neither received nor emitted any recurrent effects, which may indicate a lack of the recurrent system in these distal motor nuclei. A comparison of the recurrent pattern with the distribution of monosynaptic excitation from large muscles spindle afferents (Ia) shows that there is a partial overlap of both systems only at the elbow joint.

Reciprocal inhibition of forearm flexor muscles in spasmodic torticollis

Reciprocal inhibition between forearm extensor and flexor muscles was tested by means of an H-reflex technique in patients with spasmodic torticollis and normal controls. In both, patients and controls three different phases of reciprocal inhibition could be demonstrated with maximal inhibition at conditioning test intervals of 0 ms, 15 ms and 100 ms, respectively. However, the quantitative amount of this inhibition was different for the patients and the controls. Significantly less inhibition was found for the second and the third phase of reciprocal inhibition in the patient group. Discriminant analysis showed a clear separation between normal subjects and patients if the amount of reciprocal inhibition of the second and third phase were taken into account. We were not able to detect any side differences neither for the patients nor for the controls. The findings demonstrate a functional disturbance of motor control mechanisms of a clinically unaffected extremity in spasmodic torticollis. This is believed to reflect a bilateral disturbance most likely within the basal ganglia or their outflow. Therefore, our data support the idea, that spasmodic torticollis is associated with or even due to a generalized rather than a focal disturbance of motor control mechanisms.

Subthalamic nucleus stimulation for Parkinson's disease preferentially improves akinesia of proximal arm movements compared to finger movements

Deep brain stimulation of the subthalamic nucleus (STN‐DBS) reduces akinesia in Parkinsons disease but its impact on fine motor functions was unknown. We assessed the effects of DBS and a levodopa (L‐dopa) test on the timing of the precision grip in 18 patients. Improvement on UPDRS‐items reflecting hand functions and the shortening of the first phases of the precision grip were more distinct in the L‐dopa test than in the pure STN‐DBS condition. Other akinesia items and the time for build‐up of lifting force were equally improved in both conditions. This suggests that routine STN‐DBS might not be equally effective on all aspects of fine motor functions.

Kinematic analysis of prehension movements in children

The kinematics of the reach-to-grasp movement were analyzed in ten healthy children (age 6-7 years) under different experimental conditions: distance and size of the target objects, and visual feedback during the reach were varied in a within-subjects design. To assess age-related differences, the same experiments were performed in ten healthy adults. The experimental set-up was scaled according to body proportions to obtain equivalent conditions for both age groups. The temporal coupling between the transport and grasp components of prehension was very similar in children and adults. Peak transport velocity increased by the same factor in both age groups when the object distance was doubled. However, the decelerating approach phase was shorter in the children, who opened their hands relatively wider than adults. Unlike the adults, children failed to scale their grip aperture according to object size when visual feedback during the movement was lacking. The grip aperture increased with object distance in adults, but not in the children. The intrasubject variability of kinematic parameters was distinctly higher in the children. The results suggest that grip formation is not yet mature at an age of 6-7 years, depending more on visual feedback than in adult prehension.

Cytoarchitectonic organization of lumbar preganglionic sympathetic neurons in the cat

The location and dendritic projection of lumbar preganglionic sympathetic neurons (PSN) has been investigated in the cat. Horseradish peroxidase was either injected into lumbar paravertebral ganglia or directly applied to a lumbar ramus communicans albus. PSN were regularly found in the lateral funiculus and in the intermediate area of the ipsilateral spinal cord. They were concentrated in different nuclei: nuclei intermediolateralis pars principalis (IMLp) and pars funicularis (IMLf), nucleus intercalatus (IC) and medially near the central channel. Inconsistently, some PSN were observed in the ventral horn. Dendrites extending over a few soma were found in nearly all PSN, thus allowing description of the main dendritic projections of the preganglionic nuclei. Sometimes axons of IMLp and IC neurons could be traced into the ventral roots. In the IMLp the PSN were arranged in round clusters (up to 30 cells), which regularly followed each other in rostrocaudal direction. These clusters increased their mediolateral diameter from L1 to L4. Many cells distributed their dendrites longitudinally within the IMLp, but dendritic projections into the dorsal horn, the intermediate area and into the lateral funiculus were also frequently observed. The IMLf consisted of a few PSN only. These neurons were located in the tissue spaces between axon bundles and mediolaterally arranged, pointing towards the IMLp. The PSN of the IC were mediolaterally oriented and arranged in transverse bands extending from the lateral horn to the dorsal aspects of the central channel. All cells had mediolaterally oriented dendrites which sometimes crossed the spinal cord midline in case of the medially located neurons. The dendrites of the laterally located cells projected very often into the dorsal horn. In the medial region the PSN covered a narrow area extending from the dorsal aspects of the central channel in a ventrolateral direction up to the level of the ventral commissure. The neurons were localized in clusters and mediolaterally or longitudinally oriented. Dense clusters consisting of round cells were prevalent in the ventrolateral position. The dendrites had a rostrocaudal and mediolateral orientation and, in case of the dorsomedially located cells, sometimes crossed the spinal cord midline. The main dendritic projection areas of the different preganglionic nuclei have been compared with the location of the terminal fields of descending supraspinal and propriospinal systems and of primary afferents. It has been considered that this structural arrangement would allow for intricate interaction of the various systems with subpopulations of PSN. Thus each preganglionic nucleus might integrate specific neuronal information.

Location of lumbar preganglionic sympathetic neurones in the cat.

In the cat the distribution and projection of lumbar (L1-L4) preganglionic sympathetic neurones (PSNs) has been investigated with the horseradish peroxidase (HRP) technique. Following an HRP-injection into a lumbar sympathetic trunk ganglion, PSNs were found in the ipsilateral spinal cord in lamina VII, specially in its lateral and intermediate parts. In the medial region HRP positive cells were more frequently observed when the central, cut end of the ramus communicans albus was placed into HRP. HRP injection into the coeliac and lower mesenteric ganglia labelled lateral PSNs, but rarely medial ones. In the cranio-caudal direction, the PSNs projected over several segments via intraspinal and extraspinal pathways.

Kinetic tremor in a reach-to-grasp movement in Parkinson's disease

The aim of this study was to quantify the tremor of the hand during a natural movement (kinetic tremor) in tremor‐dominant parkinsonian patients (n = 13). We used a three‐dimensional camera system to kinematically analyze rest and kinetic tremors in an unrestrained reach‐to‐grasp movement, and additional tremor recordings were performed under standard postural and rest conditions using electromyography and accelerometry. The standard analysis showed a highly synchronized tremor with similar frequencies at rest and in sustained postural tasks, with and without loading. A kinematic recording was used to compare rest and action conditions. A strong inhibition of the resting tremor was present at the onset of the movement and reached its peak during deceleration. A kinetic tremor of low amplitude was present in most of the parkinsonian patients, but its occurrence was confined mainly to the terminal periods of the movement. The frequency of kinetic tremor was significantly higher than that at rest, before the onset of the movement in Parkinsons disease, as determined by the kinematic analysis (mean, 5.5 Hz vs 6.5 Hz; p <0.01). Our results confirm similarities between the tremor at rest and the oscillations during a sustained postural task in classic parkinsonian tremor. In contrast to this stable tremor, which seems to be generated by basal ganglia oscillators, a different pathophysiology of oscillations during motion must be considered. The kinetic tremor is most likely related to an enhancement of the physiologic tremor in the terminal phase of the reach‐to‐grasp movement.