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Digitale Medien

Influence of otolithic stimulation by horizontal linear acceleration on optokinetic nystagmus and visual motion perception (1980)

Buizza, A. ; Léger, A. ; Droulez, J. ; [weitere]

Springer

Experimental brain research 39 (1980), S. 165-176

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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

URL: http://dx.doi.org/10.1007/BF00237547

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Digitale Medien

Unidirectional habituation of vestibulo-ocular responses by repeated rotational or optokinetic stimulations in the cat (1981)

Clément, G. ; Courjon, J. H. ; Jeannerod, M. ; [weitere]

Springer

Experimental brain research 42 (1981), S. 34-42

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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

URL: http://dx.doi.org/10.1007/BF00235726

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Digitale Medien

Darstellung und Kristalldaten von LiBa2EuO4 (1967)

Bärnighausen, H. ; Schmid, R. D.

Weinheim : Wiley-Blackwell

Zeitschrift für anorganische Chemie 354 (1967), S. 27-29

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ISSN: 0044-2313

Schlagwort(e): Chemistry ; Inorganic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Beschreibung / Inhaltsverzeichnis: The new quaternary compound LiBa2EuO4 may be prepared from stoichiometric amounts of LiEuO2 and BaO by heating at 700°C under an inert atmosphere. According to Debye-Scherrer photographs. LiBa2EuO4 and LiEu3O4 are isostructural (space group Pbnm). The orthorhombic unit cell with a = 11.883, b = 12.130 and c = 3.601 Å contains 4 formula units LiBa2EuO4 (calculated density 6.369 g/cm3).

Notizen: Die neue quaternäre Verbindung LiBa2EuO4 kann aus den stöchiometrisch erforderlichen Mengen LiEuO2 und BaO durch Erhitzen bei 700°C unter Schutzgas erhalten werden. Wie aus DEBYE-SCHERRER-Aufnahmen hervorgeht, ist LiBa2EuO4 mit LiEu3O4 isotyp (Raumgruppe Pbnm). Die rhombische Elementarzelle mit a = 11,883, b = 12,130 und c = 3,601 Å enthält 4 Formeleinheiten LiBa2EuO4 (berechnete Dichte 6,369 g/cm3).

Zusätzliches Material: 1 Tab.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/zaac.19673540107

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