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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 21 (1974), S. 337-352 
    ISSN: 1432-1106
    Keywords: Motion habituation ; Optokinetic after-nystagmus ; Circular vection ; Man
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The oculomotor and perceptual after-effects (AE) of optokinetic motion stimulation as well as the adaptive changes during stimulation were studied. The intensity and duration of optokinetic after-nystagmus (OKAN) and self-motion after-sensation (CV) are a function of stimulus duration. The direction is a result of two competing processes: positive tonus continuing the actual response to the stimulus and negative tonus causing a reversal in direction. Positive AEs increase with stimulus durations up to 1 min; the negative AEs increase up to the longest stimulus duration tested (15 min) and by antagonizing the positive AEs shorten their duration once stimulus duration exceeds 3 min. Negative AEs are interpreted as the consequence of a central counter-regulation to the actual stimulus effects: motion habituation. During prolonged stimulation, motion habituation causes an apparent decrease in perceived velocity and may result in the sensation of periodic reversals of the direction of perceived self-motion, concurrent with a shift in average eye position towards the direction of the apparent reversal of self-motion, i.e. the nystagmic “Schlagfeld” reverses from the normal rapid-phase-side to the slow-phase as does also the CV. Oculomotor and perceptual AEs similarly depend on stimulus qualities (e.g. duration, area of the moving stimulus and its location in the visual field). It is argued that positive AEs are due to an imbalance induced in the vestibular nuclei by the stimulus, and it is hypothezised that motion habituation acts upon the vestibular nuclei.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 30 (1977), S. 331-338 
    ISSN: 1432-1106
    Keywords: Arm movement ; Joint receptors ; Nystagmus ; Circularvection ; Man
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary A compelling illusion of body rotation and nystagmus can be induced when the horizontally extended arm of a stationary subject is passively rotated about a vertical axis in the shoulder joint. Lateral nystagmus with the fast phase beating in the opposite direction to the arm movement was found consistently; the mean slow phase velocity increased with increasing actual arm velocity and reached about 15 °/sec; the mean position of the eyes was deviated towards the fast phase as in optokinetic nystagmus, and the nystagmus continued after the cessation of stimulation (arthrokinetic after-nystagmus). The existence of an arthrokinetic circularvection and nystagmus indicates a convergence of vestibular and somatosensory afferents from joint receptors. It is concluded that information about joint movements plays an important role within the multisensory processes of self-motion perception.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-1106
    Keywords: Motion perception ; Spatial frequency ; Aubert-Fleischl phenomenon
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Apparent velocities of moving visual stimuli are known to be different depending on whether the subject pursues the stimulus (efferently controlled motion perception) or whether the eye is stationary and the image moves across the retina (afferent motion perception). Afferent motion perception of a periodic pattern or a moving single object causes overestimation of velocity (magnitude estimations) as compared to smooth pursuit. This socalled Aubert-Fleischl phenomenon is shown to depend on local temporal frequency stimulation on the retina caused by the repetitive passage of contrast borders of the moving periodic pattern. This is evidenced by the fact that for a given stimulus speed the amount of overestimation is a function of the spatial frequency of the pattern (or the angular subtend of a single moving object) and that the Aubert-Fleischl phenomenon is not observed if a single edge moves. Background characteristics seem not to influence the apparent velocity during smooth pursuit.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-1106
    Keywords: Adaptation ; Vestibulo-ocular reflex ; Vertical eye movements ; Otoliths
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The gain of the vestibulo-ocular reflex in the sagittal plane may be due to a cooperation between otoliths and the vertical semi-circular canals. The present space experiment was aimed at studying the influence of the absence of gravity stimulation on the otoliths, by comparing VOR gain and phase in space and on ground. Measurements were taken the 5th and the 7th day of flight, the subject being asked to perform, eyes closed, active head oscillations in pitch while fixating an imaginary target in front of him. No significant decrease of the VOR gain was found in space, but a change in phase was noted. A significant increase of the VOR gain was found 14 h after landing. Control experiments have been done on ground on several subjects. They indicate that pitch VOR gain during active head movements is about one, with eyes open in darkness at 1 Hz.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 16 (1973), S. 476-491 
    ISSN: 1432-1106
    Keywords: Optokinetic stimulation ; Motion perception ; Circularvection ; Spatial orientation ; Peripheral visual field
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Optokinetic stimuli allow for two perceptual interpretations. The observer may perceive himself as being stationary in a moving surround (egocentric motion perception) or he may experience an illusion of self-motion, so that the actually moving surroundings appear to be stable (exocentric motion perception). Results 1. Circular motion of the entire surroundings (rotating drum) invariably leads to an apparent self-rotation (circularvection: CV), which is indistinguishable from an actual chair rotation. 2. Following stimulus onset, CV begins after a few seconds latency and slowly increases its apparent velocity until its saturation. CV may outlast the visual stimulus by as much as 30 sec. Latencies are independent of stimulus velocity. 3. Even with drum accelerations up to 15°/sec2, stationary subjects cannot infer from the lack of vestibular input that only the drum is rotating. 4. With stimulation of the entire visual field or sufficiently large parts of the peripheral retina, the velocity of apparent self-rotation matches stimulus speed up to 90–120°/sec. At higher speeds, CV velocity lags behind stimulus speed and results in additional egocentric motion perception. 5. Masking the central visual field by black disks up to 120° in diameter scarcely diminishes CV. Conversely, if peripheral vision is precluded, stimulation of the central field up to 30° in diameter results in exclusive egocentric motion perception of the surround. With a central and peripheral stimulus equivalent in area, the peripheral stimulus predominates CV. 6. Simultaneous presentation of conflicting central and peripheral optokinetic stimuli (i.e., stimuli rotating in opposite directions) has shown that exocentric orientation depends on the peripheral stimulus whereas optokinetic nystagmus and egocentric motion perception rely on the center of the visual field.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 656 (1992), S. 0 
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 374 (1981), S. 0 
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Der Nervenarzt 70 (1999), S. 857-858 
    ISSN: 1433-0407
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1433-8491
    Keywords: Vertebral Angiography ; Basilar Artery ; Distance to Clivus ; Variations ; Adults ; Children ; Arteriosclerosis ; Infratentorial Tumors ; Vertebralisangiographie ; A. basilaris ; Clivusabstand ; Variationen ; Erwachsene ; Kinder ; Atherosklerose ; Infratentorielle Tumoren
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Die topographischen Beziehungen der A. basilaris zu Schädelbasisstrukturen sowie Abgangsvarianzen und Kalibrigkeitsvergleiche der basisnahen Hirnarterien wurden an 63 Brachialis- und 60 Vertebralisangiogrammen quantitativ untersucht. Normbereich und Grenzwerte wurden an normalen Angiogrammen von Erwachsenen und Kindern sowie bei cerebralen Gefäßprozessen und infratentoriellen Tumoren definiert. Im normalen Angiogramm (Erwachsene) betrug der mittlere Clivus-Basilaris-Abstand vom Apex dorsi sellae 7,2 mm, vom Fußpunkt des Dorsum sellae 4,9 mm und 2 cm unterhalb des Apex 2,9 mm. Eine Basilarisanpressung ist bei 2 mm und weniger eine -abhebung bei mehr als 12 mm anzunehmen. Bei 67,6% verlief die A. basilaris in der Frontalebene mit Seitauslenkungen von weniger als 2 mm. Bei cerebraler Atherosklerose fand sich eine deutliche Elongation der A. basilaris (48,5 mm) gegenüber dem mittleren Normwert (38,5 mm) mit ausgeprägtem Basilarisüberstand oberhalb des Apex (6,6 mm) und Seitauslenkungen der Arterie bis zu 12 mm. Kinder bis zu 10 Jahren hatten weitere Basalcisternen mit einem Basilarisabstand von 7,96 mm vom Apex, vom Fußpunkt des Dorsum sellae 6,0 mm und 2 cm unterhalb des Apex von 3,8 mm. Die mittlere Basilarislänge betrug 41,5 mm. Kinder haben mit 7,8 mm den höchsten Basilarisüberstand infolge des relativen Entwicklungsrückstandes der knöchernen Schädelbasis gegenüber den Hirnstammstrukturen und Gefäßen. Bei infratentoriellen Tumoren ist eine Basilarisanpressung (weniger als 2 mm) und -abhebung (mehr als 12 mm) diagnostisch verwertbar.
    Notes: Summary Topographical correlations of the basilar artery to skull base structures as well as variations of branching and of diameter of the arteries near the base were studied by evaluating 63 brachial and 60 vertebral angiographies. Normal values were established by computing normal angiograms of adults and children. Abnormal values were found in angiograms of patients with arteriosclerosis and with infratentorial tumors. In normal angiograms (adults) the average distance between clivus and basilar artery was 7.2 mm at the apex dorsi sellae, 4.9 mm at the lower edge of the dorsum sellae and 2.9 mm at a point 2 cm below the apex. At a distance of 2 mm and less the basilar artery is pressed toward the clivus. At a distance of 12 mm and more, the basilar artery is ablated from the clivus. In 67.6% of the cases the lateral deviation of the basilar artery was less than 2 mm. Patients with cerebral arteriosclerosis showed a significant elongation of the basilar artery (48.5 mm) compared to the average normal value (38.5 mm). This elongation is combined with a marked elevation of the basilar artery above the apex (6.6 mm) and with lateral deviations up to 12 mm. Children up to 10 years had larger basal cisterns with a distance between basilar artery and clivus of 7.96 mm at the apex dorsi sellae, of 6.0 mm at the lower edge of the dorsum sellae and of 3.8 mm at a point 2 cm below the apex. The median length of the basilar artery was 41.5 mm. Children have the highest elevation of the basilar artery above the apex (7.8 mm) which is due to the relative retardation of osseous maturation of the skull base in comparison to the brain stem and vessels. It is of diagnostical value for infratentorial tumors when the basilar artery is pressed toward (less than 2 mm) or away from the clivus (more than 12 mm).
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    European archives of psychiatry and clinical neuroscience 214 (1971), S. 365-389 
    ISSN: 1433-8491
    Keywords: Optokinetic Stimulation ; Semicircular Canal Stimulation ; Circularvection ; Magnitude Estimation ; Coriolis-Effect ; Visual Pseudo-coriolis-Effect ; Dizziness ; Man ; Optokinetik ; Bogengangsreizung ; Circularvektion ; Größenschätzung ; Coriolis-Effekt ; optischer Pseudocoriolis-Effekt ; Schwindel ; Mensch
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Circularvektion und Coriolis-Phänomene wurden mit kombinierten und isolierten optokinetischen und vestibulären Drehreizen untersucht. Diese wurden durch einen Drehstuhl und eine konzentrisch dazu angeordnete zylindrische Drehtrommel dargeboten. Die durch Kopfneigung ausgelösten Coriolis-Effekte wurden durch Größenskalierung (magnitude estimation) bestimmt und Augenbewegungen, EKG sowie Atmung simultan registriert. Ergebnisse 1. Stuhl- und Trommelrotation können subjektiv nicht unterschieden werden. In beiden Fällen tritt dominant eine Eigendrehempfindung (Circularvektion) auf. Zusätzliche ortsstabile akustische Reize werden in die Eigendrehempfindung integriert. 2. Durch Kopfneigungen bei rein optokinetischem Reiz (Trommelrotation) werden Pseudocoriolis-Effekte ausgelöst, die qualitativ nicht von den vestibulären Coriolis-Effekten unterschieden werden können. 3. Die optisch-optomotorische Bewegungskontrolle (bei offenen Augen) hemmt die vestibulär ausgelösten Coriolis-Effekte richtungsspezifisch. 4. Optische Pseudocoriolis-Effekte und die Hemmung der visuellen auf die vestibuläre Afferenz sind bis zu 30 sec nach Ende des optischen Reizes nachweisbar. 5. Die stärksten Coriolis-Effekte treten bei Richtungsinkongruenz optischer und vestibulärer Bewegungsinformationen auf. Die Ergebnisse werden für die optisch-vestibuläre Integration bei Bewegungswahrnehmung und Schwindel diskutiert.
    Notes: Summary Circular vection and Coriolis effects were investigated with combined as well as with separate optokinetic and vestibular rotational stimuli using a rotary chair located inside a cylindrical rotatable drum. Coriolis effects which were elicited by tilting of the head were measured by means of the magnitude estimation technique. Bye movements, ECG, and respiration rate were simultaneously recorded. Results 1. Chair and drum rotation could not be distinguished subjectively. In both cases the experience of self-rotation (circular vection) predominated. Furthermore additional stationary acoustical stimuli were integrated into this experience. 2. Tilting of the head during pure optokinetic stimulation (rotation of the drum) produced a Pseudocoriolis effect which could not be qualitatively distinguished from the Coriolis effect produced by pure vestibular stimulation (rotation of the chair). 3. Optical-optomotor movement control (with the eyes open) inhibited the Coriolis effect produced by vestibular stimuli. This inhibition was directionally specific. 4. The visual Pseudocoriolis effect as well as the visually induced inhibition of vestibular afference outlasted the visual stimulus by up to 30 sec. 5. The strongest Coriolis-effects occurred when visual and vestibular movement information did not match. The results are discussed in terms of their significance for visual-vestibular integration in movement perception.
    Type of Medium: Electronic Resource
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