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


Autoria(s): Sommer, MA; Wurtz, RH
Data(s)

01/03/2004

Formato

1403 - 1423

Identificador

http://www.ncbi.nlm.nih.gov/pubmed/14573557

00740.2003

J Neurophysiol, 2004, 91 (3), pp. 1403 - 1423

0022-3077

http://hdl.handle.net/10161/11744

Relação

J Neurophysiol

10.1152/jn.00740.2003

Tipo

Journal Article

Cobertura

United States

Resumo

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.

Idioma(s)

eng

Palavras-Chave #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