A power law study of the edge influence on the perceived filling-in brightness magnitude

Abstract: Background: Edge plays a special role in spatial perception and as well as in determining the brightness of a surface within borders. The aim of our study was to measure threshold brightness in different levels of edges thickness. Methods: Steven's power law for circles modulating in luminance was estimated for 30 subjects (mean age 24 years, SD 3.3, 13 female). Stimuli were presented on the iMac display using the 11-bit graphic board and consisted of two circles of 3° of visual angle, separated by 10°. We tested 7 levels of Michelson contrast: 7, 8, 10, 15, 26, 50, and 100. Three edges filtering were tested (0.3, 0.8, and 1.5° of smoothing). The subjects' task was to judge the brightness of the edge filtered circle compared with the circle of the hard edge which was considered the modulus and received an arbitrary level of 50, representing the amount of brightness perception. In each trial, the same contrast level was presented in both circles. Five judgments were performed for each contrast level in edge filtering. Results: We found an increase in the power law exponent as the increase of the edge filtering (for sigma of 0.3 = 0.43, sigma of 0.8 = 0.73, and sigma 1.5 = 0.97). All power function fitting had high correlation coefficients (r2 = .94, r2 = .95, r2 = .97, respectively to sigma 0.3, 0.8, and 1.5) passing to the model's adhesion criteria. Conclusions: There was a progressive distortion on the figure brightness perception as increasing the edge filtering suggesting the control of edges on the polarity of the overall brightness. Also, perceived brightness was increasingly veridical with increased filtering, approaching 1:1 correspondence at 1.5 sigmas. (AU)

Preenchimento perceptivo da mancha cega não distorce a percepção do tamanho linear / Filling-in of the blind spot does not distort linear size perception

Ao se olhar o mundo monocularmente, não se percebe que há uma mancha cega no campo visual correspondente ao disco óptico, região da retina em que não há fotorreceptores. Ao contrário, bordas e padrões de superfícies são percebidos como se fossem detectados por fotorreceptores, fenômeno denominado preenchimento perceptivo. Para investigar se o preenchimento perceptivo distorce o espaço percebido, trinta adultos tiveram suas manchas cegas do olho direito mapeadas e fizeram as comparações de tamanho de pares de barras horizontais em condição monocular direita. Os resultados apontam uma assimetria lateral no campo visual central do olho direito nas comparações de tamanho e que o preenchimento perceptivo na mancha cega não distorce o espaço visual percebido.

When looking at the world monocularly, we do not perceive that there is a blind spot in the visual field corresponding to the optic disc, the region of the retina where there are no photoreceptors. In contrast, we perceive edges and patterns of surfaces as if were detected by photoreceptors. This phenomenon is called filling-in. To investigate whether the filling-in distorts space perception, thirty adults had their right eye blind spots mapped and they compared the length of two horizontal bars under right monocular viewing condition. The results point out a lateral asymmetry in the central visual field of the right eye in length comparisons and that the filling-in effect at the blind spot does not distort visual space perception.

Comparison of intrarectal filling with water and idling in rubber sheath with water in endoluminal ultrasonography for preoperative staging of rectal tumors / 肿瘤研究与临床

Objective To compare the value of intrarectal filling with water and filling in rubber sheath with water in endoluminal uhrasonography for preoperative staging of rectal tumors. Methods 215 cases of rectal tumors were divided into two groups. 120 cases using the method of filling in rubber sheath with water and 95 cases using intrarectal filling with water were diagnosed with uhrasonography. The results were compared with corresponding pathologic results for the judgment of their accuracy. Results The accuracy for the diagnosis of infiltration depth was 60.0 % in the first group and was 73.7 % in the second. The difference was statistically significant (P <0.05). The accuracy for diagnosis of metastases of perirectal lymph nodes was 82.5 % in the first group and was 80.0 % in the second. The difference has no statistical significance (P >0.50). Conclusion Intrarectai filling with water is better than filling in rubber sheath with water in the diagnosis of infiltration depth of rectal tumors, while there is no difference in the diagnosis of metastasis of perirectal lymph nodes.