Show Reference: "Model of the Control of Saccades by Superior Colliculus and Cerebellum"

Model of the Control of Saccades by Superior Colliculus and Cerebellum Journal of Neurophysiology, Vol. 82, No. 2. (1 August 1999), pp. 999-1018 by Christian Quaia, Philippe Lefèvre, Lance M. Optican
    abstract = {Experimental evidence indicates that the superior colliculus ({SC}) is important but neither necessary nor sufficient to produce accurate saccadic eye movements. Furthermore both clinical and experimental evidence points to the cerebellum as an indispensable component of the saccadic system. Accordingly, we have devised a new model of the saccadic system in which the characteristics of saccades are determined by the cooperation of two pathways, one through the {SC} and the other through the cerebellum. Both pathways are influenced by feedback information: the feedback determines the decay of activity for collicular neurons and the timing of the activation for cerebellar neurons. We have modeled three types of cells (burst, buildup, and fixation neurons) found in the intermediate layers of the superior colliculus. We propose that, from the point of view of motor execution, the burst neurons and the buildup neurons are not functionally distinct with both providing a directional drive to the brain stem circuitry. The fixation neurons determine the onset of the saccade by disfacilitating the omnipause neurons in the brain stem. Excluding noise-related variations, the ratio of the horizontal to the vertical components of the collicular drive is fixed throughout the saccade (i.e., its direction is fixed); the duration of the drive is such that it always would produce hypermetric movements. The cerebellum plays three roles: first, it provides an additional directional drive, which improves the acceleration of the eyes; second, it keeps track of the progress of the saccade toward the target; and third, it ends the saccade by choking off the collicular drive. The drive provided by the cerebellum can be adjusted in direction to exert a directional control over the saccadic trajectory. We propose here a control mechanism that incorporates a spatial displacement integrator in the cerebellum; under such conditions, we show that a partial directional control arises automatically. Our scheme preserves the advantages of several previous models of the saccadic system (e.g., the lack of a spatial-to-temporal transformation between the {SC} and the brain stem; the use of efference copy feedback to control the saccade), without incurring many of their drawbacks, and it accounts for a large amount of experimental data.},
    address = {Laboratory of Sensorimotor Research, National Eye Institute, Bethesda, Maryland 20892-4435, USA.},
    author = {Quaia, Christian and Lef\`{e}vre, Philippe and Optican, Lance M.},
    citeulike-article-id = {882587},
    citeulike-linkout-0 = {\&HITS=10\&hits=10\&RESULTFORMAT=\&searchid=1\&FIRSTINDEX=0\&volume=82\&firstpage=999\&resourcetype=HWCIT},
    citeulike-linkout-1 = {},
    citeulike-linkout-2 = {},
    day = {1},
    issn = {0022-3077},
    journal = {Journal of Neurophysiology},
    keywords = {ann, model, sc},
    month = aug,
    number = {2},
    pages = {999--1018},
    pmid = {10444693},
    posted-at = {2014-08-18 14:23:55},
    priority = {2},
    title = {Model of the Control of Saccades by Superior Colliculus and Cerebellum},
    url = {\&HITS=10\&hits=10\&RESULTFORMAT=\&searchid=1\&FIRSTINDEX=0\&volume=82\&firstpage=999\&resourcetype=HWCIT},
    volume = {82},
    year = {1999}

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According to Quaia, the Robinson model of saccade generation introduced the idea that saccades are controlled by a feedback loop in which the current eye position is compared to the target eye position and corrective motor signals are issued accordingly.

This idea was integrated in a family of later models.

After ablation of the SC, accurate saccades are still possible. Initially, trajectory and speed are impaired, but they recover.

Quaia et al. present a model of the saccadic system involving SC and cerebellum, which reproduces the fact that the ability to generate fast and precise saccades recovers after ablation of the SC.

Lesions to the cerebellum can permanently affect the accuracy and consistency of saccades.