What the brain stem tells the frontal cortex. II. Role of the SC-MD-FEF pathway in corollary discharge.
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 articleSubject
AnimalsBrain 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
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https://hdl.handle.net/10161/11744Published Version (Please cite this version)
10.1152/jn.00740.2003Publication 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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Show full item recordScholars@Duke
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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