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James Herman, Mark Harwood, Josh Wallman; Saccadic gain adaptation can depend on the visual context. Journal of Vision 2008;8(6):922. doi: 10.1167/8.6.922.
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When the brain is led to believe that the saccades it is generating are too large (by having a target step back while the eye is in flight), saccade amplitude gradually decreases, an adaptation widely seen as a simple form of motor learning, possibly driven by an effort to correct motor error. Not surprisingly according to this view, Deubel (1994) found that if only one of two alternately presented targets (distinct in both color and form) stepped back, adaptation was identical for both targets. Using a somewhat amended paradigm, we find differential adaptation to two visually distinct targets.
Subjects were presented with a target that either blinked at 5 Hz or was continuously illuminated; after 0.7–1.2 sec, it stepped horizontally by 9–11 deg. Throughout each experiment, only one target-type (blinking or steady) stepped back by 30% during the subject's saccade. The two targets were presented in blocks of 3–10 trials for 425 trials, and were subsequently interleaved randomly for 80 trials.
Saccades to whichever target stepped back (the adapting target) had smaller amplitudes than those made to the other target, both during the alternating blocks (0.85 vs 0.92 gain) and during the interleaved target presentation (0.82 vs. 0.91 gain). When the target type switched, the gain of the first saccade was 0.1 lower to the adapting target and 0.085 higher to the non-adapting target. The difference in gain between the targets did not exist when only one target was present during an adaptation session, except for occasional probe-trials in which the other target was present but vanished upon saccade onset.
We conclude that saccade adaptation, like many other forms of learning, can be associated with a visual context. This implies that the learning is not restricted to the motoric domain.
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