The Experts below are selected from a list of 132 Experts worldwide ranked by ideXlab platform

U. J. Ilg - One of the best experts on this subject based on the ideXlab platform.

  • Responses of primate area MT during the execution of Optokinetic Nystagmus and afterNystagmus.
    Experimental brain research, 1997
    Co-Authors: U. J. Ilg
    Abstract:

    The directional selectivity of the visual response properties was determined in 148 neurons, all located in area MT of three hemispheres of two macaque monkeys. The perferred direction of every neuron was obtained by analyzing the response obtained by a circular movement of the background while the monkeys fixated a stationary target. The distribution of the preferred directions was isotropic and showed no ipsiversive bias. MT neurons were excited in a directionally selective manner during the execution of Optokinetic Nystagmus, in a similar way to that produced by visual stimulation during fixation. The majority of neurons showed a sensitivity to the velocity of retinal image slip. Activity during the execution of Optokinetic Nystagmus could be traced back to residual retinal image slip in the direction of Optokinetic stimulation. No dynamic effects of the neuronal activity during the build-up of eye velocity in early Optokinetic Nystagmus were observed. Obviously, the activity in area MT did not reflect the charging of the velocity storage mechanism. Accordingly, following the cessation of stimulation, the activity dropped to the level of spontaneous activity and did not parallel the execution of Optokinetic afterNystagmus. These results suggest that area MT is not part of the velocity storage mechanism and, furthermore, that the storage mechanism must be downstream of area MT in the processing of visual motion for the generation of the Optokinetic Nystagmus and afterNystagmus.

Jeongmin Hwang - One of the best experts on this subject based on the ideXlab platform.

Joon Young Hyon - One of the best experts on this subject based on the ideXlab platform.

Norio Fujikawa - One of the best experts on this subject based on the ideXlab platform.

  • Influence of passive and active pendular head rotation on horizontal Optokinetic Nystagmus
    Acta oto-laryngologica. Supplementum, 1994
    Co-Authors: Norio Fujikawa, Masaaki Kitahara
    Abstract:

    The influence of pendular head rotation on Optokinetic Nystagmus was examined using a vestibulo-optic stimulator (pendular rotating chair with an optic cylinder) to study passive head rotation, and an optic cylinder which was rotated by a motor fixed to the head to study active head rotation. Pendular head rotation and optic stimuli were simultaneously and independently applied horizontally. The optic cylinder consisted of 12 vertical stripes rotating at a uniform velocity of 30°/s or 90°/s. Passive pendular head rotation was applied at a frequency of 0.1 Hz and a peak angular velocity of 30°/s. Active head rotation was applied for a period of approximately 10 s, and at an amplitude of approximately 50°. Optokinetic Nystagmus was enhanced when the head was rotated in the opposite direction to the optic cylinder. However, when the head and the optic cylinder were rotated in the same direction, Optokinetic Nystagmus was inhibited. There was little difference between the effects of passive and active head ro...

  • Influence of Pendular Head Rotation on Optokinetic Nystagmus
    Equilibrium Research, 1992
    Co-Authors: Norio Fujikawa
    Abstract:

    The influence of pendular head rotation on Optokinetic Nystagmus was studied with the use of a pendular rotating chair and an optic cylinder operated independently. Healthy subjects and patients with unilateral loss of vestibular function were examined.The pendular rotation and Optokinetic stimuli were applied in both horizontal and vertical directions. The Optokinetic stimuli consisted of 12 stripes rotating with applied uniform velocity of 90°/sec. The pendular rotation was applied at a frequency of 0.1 Hz and a peak angular velocity of 30°/sec.In healthy subjects, horizontal Optokinetic Nystagmus was promoted when the head rotated to the direction opposite to the optic cylinder rotation. On the other hand, when the head and optic cylinder rotated in the same direction, Optokinetic Nystagmus was inhibited.In patients with unilateral loss of vestibular function, a difference in response to ampullopetal and amupullofugal stimulation of the remaining intact labyrinth was seen. However, this difference gradually disappeared with compensation.In healthy subjects, vertical pendular rotation promoted and inhibited vertical Optokinetic Nystagmus.In patients with unilateral loss of vestibular function, promotion by vertical pendular rotation of vertical Optokinetic Nystagmus was the same as that in healthy subjects.The influence of active pendular head rotation on Optokinetic Nystagmus was studied with an optic cylinder fixed to the head. Inhibition of Nystagmus during active pendular head rotation was weaker than that during passive pendular head rotation, but the effect on promotion was almost the same.

James J. Harrison - One of the best experts on this subject based on the ideXlab platform.

  • Saccadic compensation for reflexive Optokinetic Nystagmus just as good as compensation for volitional pursuit
    Journal of vision, 2015
    Co-Authors: James J. Harrison, Tom C. Freeman, Petroc Sumner
    Abstract:

    The natural viewing behavior of moving observers ideally requires target-selecting saccades to be coordinated with automatic gaze-stabilizing eye movements such as Optokinetic Nystagmus. However, it is unknown whether saccade plans can compensate for reflexive movement of the eye during the variable saccade latency period, and it is unclear whether reflexive Nystagmus is even accompanied by extraretinal signals carrying the eye movement information that could potentially underpin such compensation. We show that saccades do partially compensate for Optokinetic Nystagmus that displaces the eye during the saccade latency period. Moreover, this compensation is as good as for displacements due to voluntary smooth pursuit. In other words, the saccade system appears to be as well coordinated with reflexive Nystagmus as it is with volitional pursuit, which in turn implies that extraretinal signals accompany Nystagmus and are just as informative as those accompanying pursuit.

  • Volition and automaticity in the interactions of Optokinetic Nystagmus, infantile Nystagmus, saccades and smooth pursuit
    2014
    Co-Authors: James J. Harrison
    Abstract:

    Volitional target-selecting eye movements, such as saccades or smooth pursuit, are frequently considered distinct and separate from automatic gaze-stabilising eye movements like Optokinetic Nystagmus or the vestibulo-ocular reflex. This difference is regularly mapped onto brain anatomy, with distinctions made between subcortical, automatic processes; and cortical, volitional ones. However gaze-stabilising and target-selecting eye movements must work together when a moving observer views natural scenes. Yet such co-ordination would not be possible if automatic and volitional actions are sharply divided. This thesis focuses upon interactions between gaze-stabilising and target-selecting eye movements, and how these interactions can aid our understanding of the relationship between automatic and volitional processes. For a saccade executed during Optokinetic Nystagmus to accurately land on target, it must compensate for the ongoing Optokinetic movement. It was found that targeting saccades can partially compensate for concomitant Optokinetic Nystagmus. The degree of compensation during Optokinetic Nystagmus was indistinguishable from compensation due to voluntary smooth pursuit displacements. A subsequent experiment found that locations are similarly misperceived during Optokinetic Nystagmus and smooth pursuit. Furthermore, saccade end-points are subject to the same perceptual mislocalisations. The next experiment established that fast-phases of Optokinetic Nystagmus can act like competitive saccades and cause curvature in targeting saccades. Moreover, Optokinetic Nystagmus fast-phases are delayed by irrelevant visual distractors in the same way as saccades (the saccadic inhibition effect). Lastly, it was established that the fast-phases of Infantile Nystagmus Syndrome also show the saccadic inhibition effect. In conclusion, target-selecting and gaze-stabilising eye movements show substantial co-ordination. Furthermore these results demonstrate considerable commonalties between ‘automatic’ and ‘volitional’ eye movements. Such commonalities provide further evidence there is no sharp distinction between automatic and volitional processes. Instead it is likely there are substantial interconnections between automatic and volitional mechanisms, and volition has a graded influence upon behaviour.