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Petra Kozma, Ilona Kovács, Ákos Fehér; Learning only after sleep in a contour integration task. Journal of Vision 2002;2(7):71. doi: 10.1167/2.7.71.
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Performance has been shown to improve in texture discrimination tasks 6–8 hours after training in waking state (1) or following at least an hour day-time nap (2). However, the increase is the largest after a good night's sleep of at least 6 hours (3, 4). Here we studied the effect of time between testing sessions on the performance of normal human observers in a contour integration (CI) task. The CI task involves spatial integration at a longer range than in texture discrimination tasks.
Stimuli were composed of a background of randomly oriented Gabor patches, and a closed contour defined by Gabors of the same parameters (5.0 c/deg carrier frequency, 90% contrast). In a 2AFC paradigm, observers decided whether the contour, forming a smooth egg-shape, was pointing to the right or to the left. Angular difference between the path of the contour and contour elements was varied between 0–28° in 7 levels of increasing difficulty. Five 30 minutes sessions were completed within a day in the one-day group of observers, and one session was completed daily on five consecutive days in the five-day group.
The overall performance of the one-day group did not increase by the end of the experiment, although there was a slight but statistically not significant progress in CI by the third session. There was no time-of-day effect in the five-day group. The five-day group showed significant improvement between the 1st–4th and the 1st–5th sessions.
Our results are consistent with earlier studies of perceptual learning, and confirm a slow, sleep-dependent consolidation period in a task involving long-range spatial interactions.
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