Binocular contrast gain control in natural scenes

• Main Authors: Yu-MinTai, 戴佑珉
• Other Authors: Pi-Chun Huang
• Format: Others
• Language: en_US
• Published: 2017
• Online Access: http://ndltd.ncl.edu.tw/handle/4a75zd

碩士 === 國立成功大學 === 心理學系 === 105 === The purpose of this study was to probe how remote spatial frequency information affects contrast gain control and to investigate the structure alignment of natural scenes in contrast gain control in different viewing conditions. The pattern masking paradigm was used to measure the discrimination threshold of natural scene images (targets) that were bandpass-filtered in the presence of pedestals of different contrasts. In experiment 1, three types of pedestals were adopted. The bandpass-filtered pedestal was the same as the target, the non-filtered pedestal was the original image, and the notch-filtered pedestal was filtered to remove the spatial frequency of the target information. In experiment 2, a rotated pedestal was adopted to compared with non-filtered pedestal of experiment 1. In this condition, the target was randomly rotated. The thresholds were compared among monocular, binocular, and dichoptic viewing configurations. The results of Experiment 1 showed that a classic dipper shape that was revealed for the bandpass-filtered pedestal was damaged for the non-filtered and notch-filtered pedestals. This suggests that the remote spatial frequency causes stronger inhibition in contrast gain control, or caused by the wider spatial frequency bandwidth that was overlapped to the target. The results of Experiment 2 showed that the rotated pedestal lost the facilitation effect at low pedestal contrasts whereas the nonfiltered pedestal did not. This finding suggests that the structural alignment is critical to produce the facilitation effect in contrast gain control. Furthermore, the model fitting result revealed that the notch-filtered pedestal caused slight excitation, which may actually cause by the structural alignment or the wider spatial frequency bandwidth that was overlapped with the target.