Show Reference: "On the effect of remote and proximal distractors on saccadic behavior: A challenge to neural-field models"

On the effect of remote and proximal distractors on saccadic behavior: A challenge to neural-field models Journal of Vision, Vol. 12, No. 12. (26 November 2012), doi:10.1167/12.12.14 by Soazig Casteau, Fran├žoise Vitu
@article{casteau-and-vitu-2012,
    abstract = {Two proposals have been made to account for the generation of saccadic eye movements. The first assumes that when the eyes move is under the control of a fixation gating system. The second attributes the decisions of both when and where the eyes move to the interplay between short-range excitatory and long-range inhibitory interactions within the motor map of the superior colliculus ({SC}). To distinguish both views, three behavioral experiments conducted on human participants tested the respective contributions of stimulus eccentricity and interstimulus distance on the effects of remote and proximal distractors on the latency and accuracy of saccades. Experiment 1 showed that the saccade-latency increase that results from the presentation of a remote distractor in the contralateral, nontarget hemifield varies with the ratio of distractor-to-target eccentricity, but not the interstimulus distance in visual or collicular space, thus indicating that the effect is not due to long-range inhibition. Experiments 2a and 2b showed that short-range excitation does not underlie the effect of proximal, ipsilateral distractors. Proximal distractors do not systematically shorten saccade latency, but rather show a range of effects (from a latency increase to no effect and then facilitation) as the ratio of distractor-to-target eccentricity increases, while deviating the eyes to gradually larger extents. The present findings strongly challenge the neural-field account, while suggesting that when a saccade is initiated depends mainly on the activity of a fixation gating system.},
    author = {Casteau, Soazig and Vitu, Fran\c{c}oise},
    day = {26},
    doi = {10.1167/12.12.14},
    issn = {1534-7362},
    journal = {Journal of Vision},
    keywords = {biology, eye-saccades, motor, sc, visual},
    month = nov,
    number = {12},
    pmid = {23184233},
    posted-at = {2012-12-10 11:48:10},
    priority = {2},
    publisher = {Association for Research in Vision and Ophthalmology},
    title = {On the effect of remote and proximal distractors on saccadic behavior: A challenge to neural-field models},
    url = {http://dx.doi.org/10.1167/12.12.14},
    volume = {12},
    year = {2012}
}

See the CiteULike entry for more info, PDF links, BibTex etc.

There are two hypotheses about saccadic control:

  • either there are separate, competing fixation and motion systems,
  • or there is competition between neurons in the SC coding for different motions.

According to Casteau and Vitu, a fixation population, if it exists, is probably located not in the SC but in the brainstem omnipause region.

According to Casteau and Vitu, a fixation population, if it exists, is probably located not in the SC but in the brainstem omnipause region.

Omnipause neurons (OPN) receive input from neurons across the SC, though more strongly from the rostral part.

Distractors close to a saccade target do not seem to affect saccade latency but change their landing sites.

Casteau and Vitu see the lack of a change in saccade latency due to distractors close to the saccade target as evidence against the lateral-inhibition theory of saccade generation.

Casteau and Vitu's results seem to show that it's not proximity between target and distractor but the ratio of their excentricities that saccade delay is dependent of.

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.