Dynamic overshoot in saccadic eye movements is caused by neurological control signal reversals

Bahill, A. Terry; Clark, Michael R.; Stark, Lawrence

doi:10.1016/0014-4886(75)90226-5

Cited by 163 publications

(80 citation statements)

References 38 publications

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“…This is consistent with the results of a recent study of oscillatory eye movement disorders [2]. Additionally, the mechanism by which dynamic overshoots are generated by the model suggest that the movements are caused by reversals of the saccadic control signal, as predicted by a previous study of the metrics of dynamic overshoots [12].…”

Section: Introductionsupporting

confidence: 91%

“…Moreover, the suggestion that the overshoots are attributable to oscillations of the saccadic control signal agrees with the predictions of a psychophysical study of dynamic overshoots carried out by Bahill et al [12]. Bahill et al proposed that the characterisation of the muscle plant as an overdamped harmonic oscillator implies that the reversals in eye direction observed during dynamic overshoot are likely to be caused by reversals of the saccadic control signal.…”

Section: Dynamic Overshoot Is Caused By Reversals Of the Saccadic Consupporting

confidence: 83%

“…Bahill et al proposed that the characterisation of the muscle plant as an overdamped harmonic oscillator implies that the reversals in eye direction observed during dynamic overshoot are likely to be caused by reversals of the saccadic control signal. Furthermore, they suggested that a possible physiological cause of the reversals was post-inhibitory rebound firing of the burst neurons, possibly accentuated by movements of the centre of rotation of the eye during saccades [12].…”

Section: Dynamic Overshoot Is Caused By Reversals Of the Saccadic Conmentioning

confidence: 99%

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Eye movement instabilities and nystagmus can be predicted by a nonlinear dynamics model of the saccadic system

et al. 2005

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The study of eye movement control and oculomotor disorders has, for four decades, relied on control theoretic concepts for its theoretical foundation. This paper is an example of a complementary approach based on the theory of nonlinear dynamical systems. Recently, a nonlinear dynamics model of the saccadic system was developed, comprising a symmetric piecewise-smooth system of six first-order autonomous ordinary differential equations. A preliminary numerical investigation of the model revealed that in addition to generating normal saccades, it could also simulate inaccurate saccades, and the oscillatory instability known as congenital nystagmus (CN). By varying the parameters of the model, several types of CN oscillations were produced, including jerk, bidirectional jerk and pendular nystagmus.The aim of this study was to investigate the bifurcations and attractors of the model, in order to obtain a classification of the simulated oculomotor behaviours. The application of standard stability analysis techniques, together with numerical work, revealed that the equations have a rich bifurcation structure. In addition to Hopf, homoclinic and saddlenode bifurcations organised by a Takens-Bogdanov point, the equations can undergo nonsmooth pitchfork bifurcations and nonsmooth gluing bifurcations. Evidence was also found for the existence of Hopf-initiated canards. * Now at: Mathematics Institute, University of Warwick, Coventry CV4 7AL, UK 1The simulated jerk CN waveforms were found to correspond to a pair of post-canard symmetry-related limit cycles, which exist in regions of parameter space where the equations are a slow-fast system. The slow and fast phases of the simulated oscillations were attributed to the geometry of the corresponding slow manifold. The simulated bidirectional jerk and pendular waveforms were attributed to a symmetry invariant limit cycle produced by the gluing of the asymmetric cycles.In contrast to control models of the oculomotor system, the bifurcation analysis places clear restrictions on which kinds of behaviour are likely to be associated with each other in parameter space, enabling predictions to be made regarding the possible changes in the oscillation type that may be observed upon changing the model parameters. The analysis suggests that CN is one of a range of oculomotor disorders associated with a pathological saccadic braking signal, and that jerk and pendular nystagmus are the most probable oscillatory instabilities. Additionally, the transition from jerk CN to bidirectional jerk and pendular nystagmus observed experimentally when the gaze angle or attention level is changed is attributed to a gluing bifurcation. This suggests the possibility of manipulating the waveforms of subjects with jerk CN experimentally to produce waveforms with an extended foveation period, thereby improving visual resolution.

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Section: Introductionsupporting

confidence: 91%

Section: Dynamic Overshoot Is Caused By Reversals Of the Saccadic Consupporting

confidence: 83%

Section: Dynamic Overshoot Is Caused By Reversals Of the Saccadic Conmentioning

confidence: 99%

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Eye movement instabilities and nystagmus can be predicted by a nonlinear dynamics model of the saccadic system

et al. 2005

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“…Eye movements were monitored with an infrared photoelectric method (modified from Bahill et al, 1975). Two photocells and an infrared LED were mounted on a metal bar attached to the same frame that supported the bite bar.…”

Section: Methodsmentioning

confidence: 99%

Effect of context and efference copy on visual straight ahead

Bridgeman

Graziano

1989

Vision Research

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Abstract-Biasin efferent commands to the eye changes the apparent straight ahead direction in an unstructured visual field, but has little effect in a normal visual environment. Naive subjects set a visible marker to appear straight ahead under monocular viewing conditions and while pressing on the viewing eye. Three background conditions were used: a naturalistic landscape photograph, a blank field, and a repeating checkerboard texture that provides strong contours but no information about visual direction.Effect of eyepress on straight-ahead judgments was small but significant with the landscape back8round, and larger with the blank field; the checkerboard texture yielded a bias halfway between the maguitudes of bias in the other two conditions. A visual capture theory predicts that the textured field should work like a blank one, while an oculomotor theory predicts that it should work like a natural one. Interpreted in this context, the results show the two theories to be about equally important in judging straight ahead. A second experiment with experienced observers and moving backgrounds gave the same result.

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“…In primates this is usually accomplished by fast saccadic eye movements. The high speed of saccades precludes visual feedback, yet saccades have remarkably stereotyped trajectories (Bahill et al 1975;Collewijn et al 1988;Harwood et al 1999). The peak velocity and the duration increase systematically with the amplitude of the movement, and these relationships have been called the 'main sequence' (Bahill et al 1975).…”

Section: Introductionmentioning

confidence: 99%

The Main Sequence of Saccades Optimizes Speed-accuracy Trade-off

2006

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In primates, it is well known that there is a consistent relationship between the duration, peak velocity and amplitude of saccadic eye movements, known as the 'main sequence'. The reason why such a stereotyped relationship evolved is unknown. We propose that a fundamental constraint on the deployment of foveal vision lies in the motor system that is perturbed by signaldependent noise on the motor command. This noise imposes a compromise between the speed and accuracy of an eye movement. We propose that saccade trajectories have evolved to optimize a trade-off between the accuracy and duration of the movement. Taking a semi-analytical approach we use Pontryagin's minimum principle to show that there is an optimal trajectory for a given amplitude and duration; and that there is an optimal duration for a given amplitude. It follows that the peak velocity is also fixed for a given amplitude. These predictions are in good agreement with observed saccade trajectories and the main sequence. Moreover, this model predicts a small saccadic dead-zone in which it is better to stay eccentric of target than make a saccade onto target. We conclude that the main sequence has evolved as a strategy to optimize the trade-off between accuracy and speed.

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Dynamic overshoot in saccadic eye movements is caused by neurological control signal reversals

Cited by 163 publications

References 38 publications

Eye movement instabilities and nystagmus can be predicted by a nonlinear dynamics model of the saccadic system

Eye movement instabilities and nystagmus can be predicted by a nonlinear dynamics model of the saccadic system

Effect of context and efference copy on visual straight ahead

The Main Sequence of Saccades Optimizes Speed-accuracy Trade-off

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