Reversible inactivation of macaque frontal eye field.
Abstract
The macaque frontal eye field (FEF) is involved in the generation of saccadic eye
movements and fixations. To better understand the role of the FEF, we reversibly inactivated
a portion of it while a monkey made saccades and fixations in response to visual stimuli.
Lidocaine was infused into a FEF and neural inactivation was monitored with a nearby
microelectrode. We used two saccadic tasks. In the delay task, a target was presented
and then extinguished, but the monkey was not allowed to make a saccade to its location
until a cue to move was given. In the step task, the monkey was allowed to look at
a target as soon as it appeared. During FEF inactivation, monkeys were severely impaired
at making saccades to locations of extinguished contralateral targets in the delay
task. They were similarly impaired at making saccades to locations of contralateral
targets in the step task if the target was flashed for < or =100 ms, such that it
was gone before the saccade was initiated. Deficits included increases in saccadic
latency, increases in saccadic error, and increases in the frequency of trials in
which a saccade was not made. We varied the initial fixation location and found that
the impairment specifically affected contraversive saccades rather than affecting
all saccades made into head-centered contralateral space. Monkeys were impaired only
slightly at making saccades to contralateral targets in the step task if the target
duration was 1000 ms, such that the target was present during the saccade: latency
increased, but increases in saccadic error were mild and increases in the frequency
of trials in which a saccade was not made were insignificant. During FEF inactivation
there usually was a direct correlation between the latency and the error of saccades
made in response to contralateral targets. In the delay task, FEF inactivation increased
the frequency of making premature saccades to ipsilateral targets. FEF inactivation
had inconsistent and mild effects on saccadic peak velocity. FEF inactivation caused
impairments in the ability to fixate lights steadily in contralateral space. FEF inactivation
always caused an ipsiversive deviation of the eyes in darkness. In summary, our results
suggest that the FEF plays major roles in (1) generating contraversive saccades to
locations of extinguished or flashed targets, (2) maintaining contralateral fixations,
and (3) suppressing inappropriate ipsiversive saccades.
Type
Journal articleSubject
Anesthetics, LocalAnimals
Axons
Brain Mapping
Fixation, Ocular
GABA Agonists
Lidocaine
Macaca mulatta
Muscimol
Neurons
Oculomotor Muscles
Photic Stimulation
Saccades
Sodium Channel Blockers
Visual Fields
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https://hdl.handle.net/10161/11759Collections
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Show full item recordScholars@Duke
Marc A. Sommer
Professor of Biomedical Engineering
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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