Titel: Posture and Movement: From Mice to Men
Location: University of Ulm, Oberer Eselsberg; Albert Einstein Allee 11, Hörsaal 12
Date: Tuesday, March, 21, 2000; 16:00-19:00
 
 

Dr. Florian P. Kolb
Institute of Physiology Ludwig-Maximilians-University, München
Pettenkoferstr. 12
D-80336 München
email: u7224ah@mail.lrz-muenchen.de
 

Dr. Eike D. Schomburg
Center of Physiology and Pathophysiology Georg-August-Universität Göttingen
Humboldtallee 23
D-37073 Göttingen
e-mail: eds@demeter.ukps.gwdg.de

H.-Ch. Scholle, H.-Ch. ^1*, N.P. Schumann¹, F. Biedermann¹, R. Grassme¹, K. Roeleveld¹, D.F. Stegeman^1,3 , N. Schilling², M.S. Fischer²
 

Depending on the motor task (Loeb 1984) and the actual load situation (Clamann 1979, Scholle et al. 1992) there is evidence that the activation in skeletal muscles is selective. It is supposed that morpho-functional compartmentations of muscles are the basis for such a differentiated muscle control (English and Weeks 1984, Stalberg and Eriksson 1987). The analysis of spatio-temporal muscle activation patterns permits insight into these intramuscular control processes. Therefore, we investigated the topography of surface EMG parameters above the caput laterale et longum of rat triceps brachii muscle using a 16-electrode-array (fixed under the skin directly close to the fascia). During rat's locomotion on a treadmill EMG and movement recordings (high-speed videometry / cineradiography) were simultaneously performed. After finishing the EMG investigations, the muscle fibre distribution in rat triceps muscles was three-dimensionally analysed. The slow / fast twitch fibre relations were different in the lateral and long head. Additionally, in deep parts of long head the percentage of slow twitch fibres was notedly higher. During the stance phase and the main part of swing phase of locomotion the EMG maximum was localised above the lateral triceps. The caput longum of triceps was also activated during both locomotion phases, but with lower amplitude in comparison to the lateral triceps. Only during the pre-stance phase the caput longum activity was dominating. Thus, the caput laterale seems to be responsible to generate an adequate torque especially during the stance phase. The caput longum rather realises tuning tasks. In principle, these functional differences of the both muscle heads correspond to the found muscle histology.
 

Supported by DFG, Innovationskolleg „Bewegungssysteme" FSU Jena;
¹Motor Research Grp., Inst. of Pathophysiology^, Univ. of Jena, 07740 Jena, Germany;
²Inst. of Systematic Zoology, Univ. of Jena, 07740 Jena, Germany;
³Dept. of Clin. Neurophysiology, Inst. of Neurology, Univ. of Nijmegen, The Netherlands
 

Scholle H.Ch., Prof. Dr.
Institute of Pathophysiology, Friedrich-Schiller-University Jena; Motor Research Group Erfurter Straße 35
D-07740 Jena
Tel.: 03641-937373; Fax: 03641-937377

M.S. Fischer*, H. Witte, N. Schilling, H.Ch. Scholle
 

As a key feature in therian mammal locomotion, the triceps brachii muscle is mainly responsible for the dynamic joint stabilisation and fine tuning of the body´s height. Fine adjustments are achieved by biarticular muscles known as extensors in human anatomy but used mainly to counteract gravitiy in small mammals. A unique combined analysis of force plate recordings, high frequency video, cineradiography (150 frames/sec) and topographical EMG allows to calculate torques in the elbow joint during stance phase, and to compare their timing with the overall activation pattern of the triceps brachii muscle. Different analytical approaches to describe the internal architecture of the triceps brachii muscle are presented, such as a 3D-analysis of the arrangement and length distribution or histochemical fiber typing. Structural properties of these anti-gravity muscles are distinct oxidative region with a high percentage of slow twitch type I fibers, and within these regions a fascicle orientation which differs from the rest of the muscle.
 

Fischer M.S., Prof. Dr.
Institute of Systematic Zoology and Evolutionbiology, Friedrich-Schiller-University Jena
Erbertstr. 1
D-07743 Jena
Tel. 03641-949140; Fax 03641-949142

E.D. Schomburg
 

In mammals the spinal cord deprived of all supraspinal or afferent input may generate rhythmic activities with characteristics of locomotor pattern. In spinal paralysed cats under the influence of L-DOPA rhythmic activities with different locomotor patterns may occur ("fictive locomotion"). The most common characteristics of fictive spinal locomotion resemble the activity of normal walking with a systematic alternation of flexor/extensor and right/left activity. Moreover, this pattern includes a functionally meaningful co-ordination of forelimb and hindlimb activity and rhythmic activation of trunk muscles. Regarding this pattern, one has to be aware that bifunctional muscles may be active during both flexion and extension phase. A gallop pattern, with a changed co-ordination of trunk and limb activity may occur, but does not change the basic principle of flexor-extensor alternation. Similarly, in other animals, of the same or bigger size including humans, the locomotor activity (walking) is characterised by a bilaterally alternating activity of limb flexors and extensors. If different pattern occur during normal locomotion as e.g. bilateral synchronous flexion and extension of the hindlimbs during hopping of rabbits, they are also prevalent during fictive locomotion (Viala & Buser, Exp. Brain Res. 8: 346-363, 1969). Therefore, it would be of interest to know if the predominant contribution of scapular action on propulsion in small mammals (Fischer, Zool. Anz. 238: 51-54, 1999) is spinally generated, too.

Schomburg E.D., Prof. Dr.
Center of Physiology and Pathophysiology of the Georg-August-University Göttingen
Humboldtallee 23
D-37073 Göttingen;
Tel.: 0551- 39 5927; Fax.: 0551 - 39 5923

M. Illert*, F. Caliebe, A.G. Caicoya, J. Häußler, P. Hoffmann, H. Kümmel
 

The elbow joint has been analysed in the cat with reference to the kinematic events and emg-activity during locomotion. In addition, the neuronal connections of the different motor nuclei steering this joint have been investigated in detail regarding the pathways from large muscle spindle afferents (Ia) and recurrent axon collaterals. With this background this joint may be used as a model for a hinge joint extending the body during the stance phase against gravity.

While locomoting the elbow joint is extending during the second half of the swing phase. Studies with tendon transfers make it likely that the pre-stance extensor emg-activity leading to this extension is centrally generated. This burst has a constant duration which is independent of the treadmill velocity. After the stance phase of the limb has been initiated, the yield of the elbow joint generates a massive emg-activation of the elbow extensors, which is dependent on the treadmill speed. It seems to be maintained by an afferent reflex mechanism and is specific in the different elbow extensor muscles.

The emg-recordings during locomotion and the connectivity pattern of the Ia-afferents indicate that the elbow extensors play a central role during the stance phase for organising the antigravity actions along the limb by distributing reflex excitation to wrist and shoulder motor nuclei. They feed their length signals to the shoulder extensors and rotators, and to the wrist extensors. This distribution could regulate extension at these joints in dependency on the angular excursion of the elbow joint.
 

Illert M., Prof. Dr.
Institute of Physiology, Christian-Albrechts-University Kiel
Olshausenstr. 40-60
D-24098 Kiel
Tel.: 0431- 8802032; Fax: 0431- 8804580

J. Quintern, T. Fuhr, R. Riener, T. Edrich
 

Functional electrical stimulation (FES) of peripheral nerves and muscles can replace missing signals form the central nervous system in patients with upper motor neuron lesions and restore lost motor functions. However, the patients gain only minimal functionality from currently available FES systems. The main problems of artificial motor control with FES and their possible solutions are as follows:

A) The human neuro-musculo-skeletal system is highly nonlinear. We use inverse dynamic mathematical models of this system to compensate for its main nonlinearities.

B) Spinal reflexes interact with the movement induced by FES. In stimulation experiments the tracking performance could be improved by including an inverse stretch reflex model in the control algorithm.

C) The properties of the neuro-musculo-skeletal system change rapidly due to muscle fatigue and spinal plasticity. Therefore, real-time adaptation of some of the model's parameters is necessary.

D) Complex motor tasks, e.g., stair descent, require closed-loop control. Inertial sensors (resembling the human vestibular system) and fiber-optic joint angle sensors have the potential to act as practical artificial sensors for closed-loop neural prostheses.

E) Voluntary movements of the intact parts of the nervous system must be coordinated with the motion induced by FES. We developed a strategy called "patient-driven motion reinforcement", which allows the patient to control the action of the neural prostheses.
 

Quintern J., Prof. Dr.
Department of Neurology, Ludwig-Maximilians-University of Munich; Klinikum Großhadern
Marchioninistr. 15
D-81377 München
Tel.: 089 - 7095-4818

V. Dietz*, K. Nakazawa, M. Wirz, Th.Erni
 

Recent studies have demonstrated that coordinated stepping movements can be induced in patients with complete para-/ tetraplegia, when they were standing on a moving treadmill with their body weight partially unloaded and external assistance. The aim of this study was to determine which part of the spinal cord generated the locomotor pattern. In patients with complete paraplegia due to lesions at different levels of the spinal cord, the locomotor pattern was compared to that of healthy subjects. Any similarities in electromyographic (EMG) activity of gastrocnemius and tibialis anterior muscles between the patients and healthy subjects were reflected by the analysis of the variation ratio and amplitudes of the EMG activity. It was found that the higher the level of spinal cord lesion the more 'normal' was the locomotor pattern. This suggests that neuronal circuits underlying locomotor 'pattern generation' in man are not restricted to any specific level(s) of the spinal cord, but that an intricate neuronal network contributing to bipedal locomotion extends from thoraco-lumbal to cervical levels.
 

Reference: Dietz V, Nakazawa K, Wirz M, Erni Th (1999) Level of spinal cord lesion determines locomotor activity in spinal man. Exp Brain Res 128: 405-409.

Dietz V., Prof. Dr.
Paraplegic Centre, University Hospital Balgrist, Zürich; Switzerland
Forchstrasse 340
CH-8008 Zürich, Switzerland
Tel.: 0041 -1 - 386 39 01, Fax.: 0041 - 1 - 386 39 09

---

Distribution of primary afferent collaterals in cross section of spinal cord
R. Cajal: Histologie du système nerveux, Paris, Maloine, 1909