1,721,926 research outputs found
Visual-vestibular interaction in oculomotor control: a model interpretation of pathological situations.
No full textOculomotor responses to combined optokinetic and vestibular stimulations in labyrinthine and cerebellar defective patients are discussed in terms of parametric changes in a model describing the interaction between the vestibulo-ocular reflex (VOR) and the optokinetic reflex (OKR). The experimental results obtained by several authors can correctly be predicted and explained by the model. The model is also shown to help assessing the validity and the diagnostic significance of the procedures used to test VOR-OKR interaction
New experimental data on cat's optokinetic response. Is there need to revise previous models of the optokinetic reflex?
No full textNew data on cat's optokinetic reflex (OKR) available in the literature have been interpreted by using a nonlinear model of OKR previously proposed by the authors. A general agreement between experimental data and theoretical predictions was obtained, and some features of the former could be explained as consequences of the intrinsic nnonlinearity of OKR. In contrast with recent statements appeared in the literature, it was concluded that the new data seem to confirm, rather than disprove, the previous model of cat's OKR
Visual-vestibular interaction in the control of eye movements: mathematical modelling and computer simulation
No full textAn improved non-linear mathematical model of visuo-vestibular interaction during combined vestibular and optokinetic stimulation is presented and validated against almost all the experimental data on monkeys and cats available in the literature. The model is proven to be able to reproduce both oculomotor responses and neural activity at the level of vestibular nuclei and in the vestibulo-cerebellum
Model interpretation of visual-vestibular interaction in patients with labyrinthine and cerebellar pathologies
No full textOculomotor responses to combined optokinetic and vestibular stimulations in labyrinthine and cerebellar defective patients are discussed in terms of parametric changes in a model describing the interaction between the vestibulo-ocular reflex (VOR) and the optokinetic reflex (OKR). By making a few reasonable hypotheses about model parameter variations in relation to the type of pathology, the experimental results obtained by several authors can correctly be predicted and explained by the model. The model can therefore be used to define a set of parameters giving an estimate of the state of the system subserving VOR-OKR interaction in the examined patients. The model is also shown to be a powerful tool to assess the validity and the diagnostic significance of the procedures used to test VOR-OKR interaction
Velocity characteristics of smooth pursuit eye movements to different patterns of target motion.
No full textHorizontal smooth pursuit eye movements were recorded in normal subjects in response to different patterns of target motion that was either periodic or not. Periodic patterns were triangular and sinusoidal waves. Non-periodic patterns were ramps with either constant or sinusoidally varying velocity. In both cases, several different amplitudes and peak velocities were considered. The experimental results indicate that (a) the performance of the smooth pursuit system depends on the spatio-temporal characteristics of target motion, (b) the relationship between smooth pursuit eye velocity and target velocity during the tracking of constant velocity ramps is strongly nonlinear with a saturation depending on the amplitude of target excursion, (c) in the remaining experimental conditions, there is a linear behaviour up to target velocities of 75 deg/s with a gain of about 0.9
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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