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    What the brain stem tells the frontal cortex. II. Role of the SC-MD-FEF pathway in corollary discharge.

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    Date
    2004-03
    Authors
    Sommer, Marc A
    Wurtz, RH
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    Abstract
    One way we keep track of our movements is by monitoring corollary discharges or internal copies of movement commands. This study tested a hypothesis that the pathway from superior colliculus (SC) to mediodorsal thalamus (MD) to frontal eye field (FEF) carries a corollary discharge about saccades made into the contralateral visual field. We inactivated the MD relay node with muscimol in monkeys and measured corollary discharge deficits using a double-step task: two sequential saccades were made to the locations of briefly flashed targets. To make second saccades correctly, monkeys had to internally monitor their first saccades; therefore deficits in the corollary discharge representation of first saccades should disrupt second saccades. We found, first, that monkeys seemed to misjudge the amplitudes of their first saccades; this was revealed by systematic shifts in second saccade end points. Thus corollary discharge accuracy was impaired. Second, monkeys were less able to detect trial-by-trial variations in their first saccades; this was revealed by reduced compensatory changes in second saccade angles. Thus corollary discharge precision also was impaired. Both deficits occurred only when first saccades went into the contralateral visual field. Single-saccade generation was unaffected. Additional deficits occurred in reaction time and overall performance, but these were bilateral. We conclude that the SC-MD-FEF pathway conveys a corollary discharge used for coordinating sequential saccades and possibly for stabilizing vision across saccades. This pathway is the first elucidated in what may be a multilevel chain of corollary discharge circuits extending from the extraocular motoneurons up into cerebral cortex.
    Type
    Journal article
    Subject
    Animals
    Brain Stem
    Frontal Lobe
    Functional Laterality
    GABA Agonists
    Macaca mulatta
    Mediodorsal Thalamic Nucleus
    Microinjections
    Motor Neurons
    Muscimol
    Psychomotor Performance
    Saccades
    Sleep Stages
    Superior Colliculi
    Vision, Ocular
    Visual Fields
    Visual Pathways
    Permalink
    https://hdl.handle.net/10161/11744
    Published Version (Please cite this version)
    10.1152/jn.00740.2003
    Publication Info
    Sommer, Marc A; & Wurtz, RH (2004). What the brain stem tells the frontal cortex. II. Role of the SC-MD-FEF pathway in corollary discharge. J Neurophysiol, 91(3). pp. 1403-1423. 10.1152/jn.00740.2003. Retrieved from https://hdl.handle.net/10161/11744.
    This is constructed from limited available data and may be imprecise. To cite this article, please review & use the official citation provided by the journal.
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    Scholars@Duke

    Sommer

    Marc A. Sommer

    W. H. Gardner, Jr. Associate Professor
    We study circuits for cognition. Using a combination of neurophysiology and biomedical engineering, we focus on the interaction between brain areas during visual perception, decision-making, and motor planning. Specific projects include the role of frontal cortex in metacognition, the role of cerebellar-frontal circuits in action timing, the neural basis of "good enough" decision-making (satisficing), and the neural mechanisms of transcranial magnetic stimulation (TMS).
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    Articles written by Duke faculty are made available through the campus open access policy. For more information see: Duke Open Access Policy

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