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Abstract:
The use of stochastic modeling techniques has provided many
insights into the processing architecture of the oculomotor system.
The present work evaluates the issue of saccadic target selection
using these techniques. Eye position was monitored using the
scleral search coil technique. Visual targets were located at 4, 8,
12, and 28 degrees of visual angle in each visual hemifield.
Observers were presented with redundant visual targets and made
saccades which either acquired one of the targets accurately
(bistable saccades) or landed at an intermediate location
(averaging saccades). Averaging saccades were hypothesized to be
the result of sensory pooling, while bistable saccades were
hypothesized to be due to response competition between incompatible
motor programs. Contrary to these predictions, the results were
consistent with the hypothesis that response competition is in
operation during both averaging and bistable saccades.
Additionally, the response competition created by targets which
were incompatible in terms of direction alone took longer (~ 20
milliseconds) to resolve than that created by targets which were
incompatible in terms of amplitude alone. These results are
discussed in terms of their implications for models of saccadic
programming and their relation to recent neurophysiological
findings.
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