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Sara C. Mednick, Geoffrey M. Boynton; Perceptual deterioration is specific to background and target orientation.. Journal of Vision 2004;4(8):292. doi: 10.1167/4.8.292.
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Repeated within day testing on a texture discrimination task leads to retinotopically specific decreases in performance (Mednick et al, 2002). While perceptual learning has been shown to be highly specific to the spatial location and characteristics of the trained stimulus, the specificity of perceptual deterioration has not been studied. We investigated the similarities between learning and deterioration by examining whether deterioration transfers to new background or target orientations. Subjects performed a texture discrimination task in four one-hour sessions at 9AM, 12PM, 4PM & 7PM. Performance was measured as the threshold inter-stimulus-interval (ISI) between the target and masking stimulus (Karni & Sagi, 1991). The task and stimuli were the same for the first three sessions for all subjects, but for a subset of the subjects we changed the orientation of either the background or the target by 90 degrees in the last session (7PM). As expected, performance deteriorated across the first three sessions. However, performance recovered to baseline levels in the last session when either the background orientation or the target orientation changed. Thus, unlike perceptual learning (Karni & Sagi, 1991), deterioration shows specificity not only for the trained background orientation but also for the target orientation. The stimulus specificity of our results shows that deterioration in texture discrimination is not caused by a general increase in fatigue or decline in motivation. Rather, perceptual deterioration appears to be caused by fatigue of a specific population of neurons in early visual cortex tuned to discriminate specific orientation differences between target and background.
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