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  • Eye movements  (3)
  • Cat  (2)
  • Achsenfehlstellung und Beinlängendifferenz  (1)
  • 1
    ISSN: 1432-1106
    Schlagwort(e): Vestibular system ; Optokinetic ; Otoliths ; Eye movements ; Motion perception
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Several studies in the past have demonstrated the existence of an Otolith-Ocular Reflex (OOR) in man, although much less sensitive than canal ocular reflex. The present paper 1 confirms these previous results. Nystagmic eye movements (L-nystagmus) appear in the seated subject during horizontal acceleration along the interaural axis in the dark for an acceleration level (1 m/s2) about ten times the perception threshold with a sensitivity of about 0.035 rad/m. When sinusoidal linear acceleration is combined with optokinetic stimulation, the recorded nystagmus slow phase velocity exhibits strong periodic modulation related to subject motion. This marked effect of linear acceleration on the optokinetic nystagmus (OKN) appears at a level (0.1 m/s2) close to the acceleration perception threshold and has a 4-fold higher sensitivity than L-nystagmus. Modulation of OKN can reach a peak-to-peak amplitude as great as 20 °/s; for a given optokinetic field size it increases with the velocity of the optokinetic stimulus, i.e. with the slow phase eye velocity. In parallel with changes in OKN slow phase velocity, linear acceleration induces a motion related decrease in the perceived velocity of the visual scene and modifications in selfmotion perception. The results are interpreted in terms of a mathematical model of visual-vestibular interaction. They show that sensory interaction processes can magnify the contribution given to the control of eye movements by the otolithic system and provide a way of exploring its function at low levels of acceleration.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    Experimental brain research 36 (1979), S. 509-522 
    ISSN: 1432-1106
    Schlagwort(e): Acoustic ; Vestibular ; Otoliths ; Eye movements ; Linear acceleration
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary In order to examine otolithic contribution to eye movements ten subjects were asked to track either a moving acoustic target or a stationary target during subect linear motion on a cart. The relative displacement between the subject and the target was the same in the two situations. Recordings of eye movements during subject lateral acceleration in the dark without any task, or with the task of tracking an imagined stationary target were made as a control. The frequencies ranged between 0.15 and 0.3 Hz and peak acceleration between 0.55 and 1.2 m/s2. No lateral eye movements (L-nystagmus) were recorded in the dark. Only saccadic eye movements were recorded during the tracking of a moving acoustic target. Slow eye movements interspersed by saccades were observed when the moving subject tracked an imagined or an acoustic stationary target. Contribution of the slow phase to tracking was more important in the presence of an acoustic target than in the presence of imagined target. The results are interpreted in terms of an otolithic contribution to the central reconstruction of the acoustic target velocity, or in terms of an adaptive control of the otolithic-ocular reflex gain. A conceptual model accounting for these interpretations is proposed.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    Springer
    Experimental brain research 28 (1977), S. 235-248 
    ISSN: 1432-1106
    Schlagwort(e): Vestibulo-ocular reflex ; Hemilabyrinthectomy ; Role of vision ; Cat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary 1. A new description of vestibulo-ocular responses to angular velocity steps has been used to quantify vestibular compensation in right hemilabyrinthectomized cats. The amplitudes (VM and CM) and the times of occurrence (tM and to) from stimulus onset of the peaks of slow phase eye velocity and slow cumulative eye position were computed for velocity steps directed towards the lesioned side (clockwise, CW) and towards the intact side (counterclockwise, CCW). In addition, the values of these parameters were corrected from the effects of spontaneous nystagmus, when present. 2. In animals recovering in normal laboratory conditions, spontaneous nystagmus disappeared within 10 days after operation. In CCW responses, vm decreased by about 45% during the first 3 days and then remained stationary during the next 2 weeks. In CW responses VM showed a rapid increase during the first 3 days, and then remained stationary. After 2 weeks, VM increased in both CW and CCW responses. CM changes substantially reproduced those of VM. 3. In animals put in the dark immediately after operation, spontaneous nystagmus persisted until re-exposure to light (up to 31 days) and then disappeared rapidly. VM in both CW and CCW responses remained at a low value during the dark period and became more or less doubled after one week of exposure to light. CM also increased rapidly in CW and CCW responses, after re-exposure to light. 4. In the discussion these results are compared with those concerning activity of single vestibular neurons during compensation. It is concluded that vision is a primary factor conditioning disinhibition of vestibular nuclei spontaneous activity after the critical phase of compensation.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 4
    ISSN: 1432-1106
    Schlagwort(e): Vestibulo-ocular reflex ; Optokinetic nystagmus ; Vestibular habituation ; Cat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary 1.Unilateral habituation of the vestibuloocular reflex was produced in adult cats stimulated by repeated unidirectional velocity steps (vestibular training) or by a continuously moving visual surround (optokinetic training). — 2. Unidirectional vestibular training produced a strong asymmetry of vestibuloocular responses (VOR). Responses to velocity steps applied to the “trained” labyrinth were decreased both in gain and in time-constant. This effect generalized to responses to sinusoidal oscillations (0.03 Hz to 0.1 Hz), i.e. to a stimulus not used during training. — No spontaneous nystagmus was ever observed in spite of the dynamic VOR asymmetry. — 3. Unilateral vestibular habituation produced by vestibular training appeared to be a long-lasting phenomenon. It was still present 10 days after the end of training. — 4. Optokinetic responses were not affected by vestibular training. — 5. Unidirectional optokinetic training produced an increase in the slow phase velocity of optokinetic nystagmus (OKN) by about 25% in both directions. This effect did not persist for more than a few minutes. A marked spontaneous nystagmus was recorded in the dark after each session of optokinetic training, with a slow phase in the direction opposite to the previous OKN. — 6. VOR in response to velocity steps and to sinusoidal oscillations were decreased unilaterally after optokinetic training. This effect was of short duration, however, and disappeared within the interval between training sessions. This lack of retention contrasted with the prolonged effect of vestibular training.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 5
    Digitale Medien
    Digitale Medien
    Springer
    Medical & biological engineering & computing 27 (1989), S. 617-622 
    ISSN: 1741-0444
    Schlagwort(e): Dynamics ; Eye movements ; Nonlinear gain ; Smooth pursuit
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie , Medizin
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 6
    Digitale Medien
    Digitale Medien
    Springer
    Der Orthopäde 29 (2000), S. 821-831 
    ISSN: 1433-0431
    Schlagwort(e): Schlüsselwörter Kongenitale Tibiapseudarthrose ; Ilizarov-Methode ; Simultane Korrektur von Pseudarthrose ; Achsenfehlstellung und Beinlängendifferenz ; Keywords Congenital pseudarthrosis of the tibia ; Circular frame technique ; Simultaneous correction of pseudarthrosis ; Length discrepancy and axial deformity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Beschreibung / Inhaltsverzeichnis: Abstract Congenital pseudarthrosis of the tibia (CPT) is one of the most challenging conditions in paediatric orthopaedics. The history of CPT treatment ischaracterised by repeatedly ineffective surgical interventions with the inevitable outcome of severe disability. Most procedures failed to account for the complexity of the problem. The past two decades have witnessed more experience having been gained with the Ilizarov technique. This method provides a comprehensive approach to all aspects of CPT problem, allowing the surgeon to simultaneously address the problems of union as well as those of deformity, length discrepancy joint function, ankle valgus and weight bearing. It appears that the goal to achieve stable fusion before the child begins school is attainable. In the pre-pseudoarthrotic stage, bracing should be preferred to surgery until the patient is in an older age group. This study reports on the results of 19 patients: 15 have finished treatment, and 14 of them with a stable fusion at follow-up. The results were highly encouraging in reaching the ultimate goal of avoiding amputation and achieving a well-functioning limb.
    Notizen: Zusammenfassung Die kongenitale Tibiapseudarthrose gehört zu den schwierigsten Krankheitsbildern in der Kinderorthopädie. Anamenstisch findet sich bei diesen Patienten meist eine Vielzahl ineffektiver, operativer Eingriffe und letztendlich auch ein funktionell unbefriedigendes Ergebnis in Form einer den Patienten schwer behindernden Deformität. Bei den meisten dieser Behandlungsverfahren wird der Komplexität des Problems kongenitale Tibiapseudarthrose nicht entsprechend Beachtung geschenkt. In den letzten Jahren wurden deshalb Verfahren entwickelt, die eine erfolgreiche Behandlung ermöglichen. Es handelt sich dabei um den vaskularisierten Fibulatransfer und die Ilizarov-Technik. Letzterer muss unserer Meinung nach deshalb der Vorzug gegeben werden, da sie dem behandelnden Orthopäden die Möglichkeit gibt simultan sowohl Pseudarthrose, als auch Achsendeformität, Beinlängendifferenz, und Sprunggelenkvalgus zu behandeln. Weiter hat sich gezeigt, dass allzu frühe operative Eingriffe ungünstig sind und dass es sinnvoll ist, primär eine konsequente konservative Therapie durchzuführen, um im Alter von 3–6 Jahren operativ eine stabile Fusion der Pseudarthrose mit Korrektur der Begleitdeformität zu erreichen. Die vorliegende Arbeit berichtet über eigene Ergebnisse bei 19 Patienten, von denen bei 15 die Behandlung abgeschlossen wurde, wobei bei 14 Patienten eine stabile Fusion zum Zeitpunkt der Nachuntersuchung erzielt werden konnte. Die Ergebnisse waren sowohl klinisch als auch funktionell äußerst zufriedenstellend und lassen den Schluss zu, dass eine erfolgreiche Behandlung der Tibiapseudarthrose heute möglich ist und eine Amputation daher als obsolet angesehen werden muss.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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