Clinical Neuroscience

[A NEURO-MECHANICAL TRANSDUCER MODEL FOR CONTROLLING JOINT ROTATIONS AND LIMB MOVEMENTS]

LACZKÓ József, KERRY Walton, RODOLFO Llinas

JANUARY 30, 2006

Clinical Neuroscience - 2006;59(01-02)

[Here we report on the development of an integrated general model for the control of limb movements. The model computes muscle forces and joint rotations as functions of activation signals from motoneuron pools. It models the relationship between neural signals, muscle forces and movement kinematics by taking into account how the discharge rates of motoneuron pools and the biomechanical characteristics of the musculoskeletal system affect the movement pattern that is produced. The lengths and inertial properties of limb segments, muscle attachment sites, the muscles’ force-length, force-frequency and force-velocity (of contraction) relationships, as well as a load parameter that simulates the effect of body weight are considered. There are a large number of possible ways to generate a planned joint rotation with muscle activation. We approach this “overcompleteness problem” by considering each joint to be controlled by a single flexor/extensor muscle pair and that only one of the two muscles is activated at a given time. Using this assumption, we have developed an inverse model that provides discharge rates of motoneuron pools that can produce an intended angular change in each joint. We studied the sensitivity of this inverse model to the muscle force-length relationship and to limb posture. The model could compute possible firing rates of motoneuron pools that would produce joint angle changes observed in rats during walking. It could also compare motoneuron activity patterns received for two different hypothetical force-length relations and show how the motoneuron pool activity would change if joints would be more flexed or extended during the entire movement.]

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Clinical Neuroscience

[COMPLEX TREMOR ANALYSIS FOR THE DIFFERENTIAL DIAGNOSIS OF ESSENTIAL TREMOR AND PARKINSON’S DISEASE]

FARKAS Zsuzsanna, CSILLIK Anita, PÁLVÖLGYI László, TAKÁCS Annamária, SZIRMAI Imre, KAMONDI Anita

[Objective - Tremor is the most common movement disorder which is most often either essential or caused by Parkinson’s disease. The differentiation of these disorders at the initial stage may be difficult. Objective assessment of the efficacy of tremor medications is only possible by instrumental measurements. The aim of this study was to determine whether the computer assisted tremor analysis system CATSYS 2000 can help in the differentiation of parkinsonian from essential tremor. Methods - The rhythmicity and maximal frequency of fast alternating hand and finger movements, simple reaction time and postural instability were recorded in healthy controls (n=18), patients with Parkinson’s disease (n=39) and essential tremor (n=37). Data were digitally converted and statistically analyzed. Results - Tremor intensity, median frequency and frequency distribution showed characteristic differences in the three groups. Performance in fast alternating movements of hands and fingers were significantly worse in both tremor groups compared to the healthy controls. Conclusions - The data also indicated that quantitative measurements of tremor parameters must be performed on both sides, because the presence of significant side differences support the diagnosis of Parkinson’s disease. The method presented can be used to objectively analyze tremor and performance in rhythmic movements. The results show that it helps to differentiate parkinsonian from essential tremor as well as to predict disease course and the effectiveness of therapy. Multivariate statistical analysis of tremor and movement performance also provides an opportunity to study the pathogenesis of human tremor.]

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[THE SIGNIFICANCE OF CHLAMYDIA PNEUMONIAE IN SELECTED NEUROLOGIC DISORDERS]

HORVÁTH Zoltán, VÉCSEI László

[Chlamydia pneumoniae has recently been implicated in the pathogenesis of several neurological diseases. As an intracellular parasite with its unusual life cycle it is able to circumvent the immune system and to persist in the organism. It has the ability to modify the function of the infected cell and supposedly induce autoimmune reactions. These properties can make it pathogenic in several chronic neurological diseases including multiple sclerosis, atherosclerosis, stroke, Alzheimer dementia and giant cell arteriitis. The evaluation of the available, often contradictory, data that are based on various different methods is not easy. The importance of the issue is enhanced by the potential need for antibiotic treatment.]

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[CONGRESS CALENDAR]

[Congress calendar 2006;59(01-02)]

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Clinical Neuroscience

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