Show Reference: "Look Away: the Anti-Saccade Task and the Voluntary Control of Eye Movement"

Look Away: the Anti-Saccade Task and the Voluntary Control of Eye Movement Nature Reviews Neuroscience, Vol. 5, No. 3. (01 March 2004), pp. 218-228, doi:10.1038/nrn1345 by Douglas P. Munoz, Stefan Everling
@article{munoz-and-everling-2004,
    abstract = {The anti-saccade task has emerged as an important task for investigating the flexible control that we have over behaviour. In this task, participants must suppress the reflexive urge to look at a visual target that appears suddenly in the peripheral visual field and must instead look away from the target in the opposite direction. A crucial step involved in performing this task is the top-down inhibition of a reflexive, automatic saccade. Here, we describe recent neurophysiological evidence demonstrating the presence of this inhibitory function in single-cell activity in the frontal eye fields and superior colliculus. Patients diagnosed with various neurological and/or psychiatric disorders that affect the frontal lobes or basal ganglia find it difficult to suppress the automatic pro-saccade, revealing a deficit in top-down inhibition.},
    author = {Munoz, Douglas P. and Everling, Stefan},
    day = {01},
    doi = {10.1038/nrn1345},
    issn = {1471-003X},
    journal = {Nature Reviews Neuroscience},
    keywords = {aes, basal-ganglia, biology, motor, rls, sc, sc-input, suppression, top-down, visual},
    month = mar,
    number = {3},
    pages = {218--228},
    pmid = {14976521},
    posted-at = {2011-12-02 09:28:56},
    priority = {2},
    publisher = {Nature Publishing Group},
    title = {Look Away: the {Anti-Saccade} Task and the Voluntary Control of Eye Movement},
    url = {http://dx.doi.org/10.1038/nrn1345},
    volume = {5},
    year = {2004}
}

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DLPFC projects directly to the SC.

Correct pro-saccades are executed earlier than correct anti-saccades.

In saccade/anti-saccade experiments, direction errors are confined to the anti-saccade condition.

In anti-saccade experiments, incorrect saccades (those in the direction of the visual stimulus) occur earlier after target onset than do correct anti-saccades.

The timing of correct pro-saccades has a bi-modal distribution. One class of pro-saccades happens very fast (express saccades), the others take a little longer.

Express saccades are thought of as reflex behavior. The reflex behind them is referred to as the 'visual grasp reflex'.

They are believed to be the result of a direct translation of a visual stimulus into a motor command.

In anti-saccade conditions, the `visual grasp reflex' must be suppressed.

One family of models for saccades and anti-saccades are the `accumulator models'.

These models pose that activation of saccade and saccade suppression neurons race each other. The one first to reach a threshold wins.

Activation of FEF and SC neurons is higher before direction error saccades in anti-saccade tasks than before correct anti-saccades.

Munoz and Everling assume that there are distinct populations of fixation and saccade neurons in the SC and FEF.

In a more recent paper, Casteau and Vitu state that there is some debate about that. However, they, too argue for distinct fixation neurons. On the other hand, they also state that fixation neurons probably are not located in the SC itself, which is in contrast of what Munoz and Everling write.

Omnipause neurons in the reticular formation tonically inhibit `the saccade-generation circuit'.

It seems unclear what is the original source of SC inhibition in preparation of anti-saccades. Munoz and Everling cite the supplementary eye fields (SEF), dorsolateral prefrontal cortex (DLPFC) as possible sources, and the substantia nigra pars reticulata (SNpr).

The supplementary eye fields (SEF) and dorsolateral prefrontal cortex (DLPFC) both project directly to the SC.

LIP may be where anti-saccade targets are decided upon.

The superior colliculus sends motor commands to cerebellum and reticular formation in the brainstem.

The cerebellum sends motor commands to the reticular formation

It is the reticular formation that initiates saccades.

Lateral intraparietal area (LIP) projects to intermediate layers of SC.