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Kyung Mi Park, Sang Chul Chong; Representation of mean spatial frequency. Journal of Vision 2008;8(6):944. doi: 10.1167/8.6.944.
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© ARVO (1962-2015); The Authors (2016-present)
Statistical properties of visual arrays can be used as summary representation of a complex scene. Current study investigated how we summarized various spatial frequencies (SF) and whether the visual system could be adapted to this summary. In Experiment 1, we investigated how we perceived different SFs using the magnitude estimation procedure. The magnitude of perceived SF followed a power function with an exponent of 1.13. In Experiment 2, participants were asked to estimate the mean SF of two different gratings. For the two different gratings, five pairs of different spatial frequencies were used (1-4, 1.5-6, 2-8, 2.5-10, 3-12 cpd). The estimated mean SFs based on the psychometric function found in Experiment 1 were a good approximation of participants' estimates of mean SF. These results suggest that mean SF is calculated on psychological scale. In Experiment 3, we first measured the contrast threshold for each participant using QUEST. We then had participants adapt to either two gratings with different SFs (separated by 2 octaves) or one of the two gratings. When participants were adapted to the two gratings, the two adaptors were intermittently presented for 4 minutes and they took turns in every 2 seconds. The adaptor was presented for 2 minutes when they were adapted to one of the two gratings. To maintain adaptation, we used 4-second top-up. The contrast threshold of mean SF was significantly elevated when the participants were adapted to the two gratings, whereas it was not elevated when they were adapted to only one of the two gratings. When we measured the contrast threshold using the same gratings as the adaptors rather than mean-SF grating, the contrast threshold was significantly elevated. Our findings suggest that the visual system represents mean SF as well as individual SFs.
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