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Summary: Abstract We measured the gain and phase of horizontal
and vertical vergences of five subjects as a function of
stimulus area and position. Vergence eye movements
were recorded by the scleral search coil method as sub-
jects observed dichoptic displays oscillating in antiphase
either from side to side or up and down with a peak-to-
peak magnitude of 0.5° at either 0.1 Hz or 1.0 Hz. The
stimulus was a central textured disc with diameter rang-
ing from 0.75° to 65°, or a peripheral annulus with outer
diameter 65° and inner diameter ranging from 5° to 45°.
The remaining field was black. For horizontal vergence
at both stimulus frequencies, gain and the phase lag were
about the same for a 0.75° stimulus as for a 65° central
stimulus. For vertical vergence, mean gain increased and
mean phase lag decreased with increasing diameter of
the central stimulus up to approximately 20°. Thus, the
stimulus integration area is much smaller for horizontal
vergence than for vertical vergence. The integration area
for vertical vergence is similar to that for cyclovergence,
as revealed in a previous study. For both types of ver-
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