Color noise influence for luminance discrimination

LACERDA, E. M. C. B.; CORMENZANA MÉNDEZ, IÑAKI; MARTÍN, ANDRÉS; SOUZA, GIVAGO S; O'DONELL, BEATRIZ

Campos do Jordão, SP

Congreso; XXXII Reunião Anual da Federação de Sociedades de Biologia Experimental - FeSBE; 2017

Federação de Sociedades de Biologia Experimental - FeSBE

Color noise influence on the reaction time for luminance discriminationLacerda, E. M. C. B. , Méndez, I. C. , Martín, A. , Souza, G. S. , O`Donell, B. ,Centro de Ciências da Saúde - UNICEUMA Departamento luminotécnica Luz & Vista - UNT Laboratório de Neurologia Tropical - UFPAIntrodução:Introduction. Some stimuli simulate natural scenes with mixture of luminance and color contrast, as occur with pseudoisochromatic stimulus, used to investigate color vision. The same rationale done for pseudoisochromatic design could be applied for new stimulus that aim to investigate the luminance vision.Objetivos:Aim. To evaluate the influence of color noise magnitude in detection reaction time for luminance discrimination task.Métodos:Methods. This work was approved by the Ethics Committee (report # 570.434). We evaluated 5 trichromat subjects with 20/20 visual acuity, from 30 to 35 years-old, of both gender. The stimuli were developed using Psychtoolbox in MATLAB R2010a language programing. The stimulus was composed by mosaic of circles with 10 different sizes (spatial noise). Each circle of the stimulus had one out of 16 chromaticities (chromaticity noise) around a central chromaticity. A target differed from the background by luminance contrast. The target was composed by a mosaic of circles that shared the same luminance and perceptually seemed to a Landolt C with 4.4° visual angle of outer diameter, 2.2° visual angle of inner diameter, and with gap of 1° visual angle. Initially, the target luminance presented 4 cd/m2 and background luminance was 40 cd/m2 (Weber contrast = 88.8%). To measure the reaction time, after stimulus presentation, the subject then pressed a button box (modified USB mouse) to indicate the C gap orientation as soon as he/she had detected. The time between the presentation of the stimulus and the observers response was registered as the reaction time. Only the correct positional responses were considered in the analysis of reaction time. It was used Factorial ANOVA (considering p<0.05 with 0.95 confidence interval) to calculate the results.Resultados:Results. Reaction time gets worse as the vector distance grows. The minimum time of reaction corresponds to the achromatic noise (Current effect: F (4, 1488) = 17.228, p<0.001). The noise masks the stimulus (Current effect: F (9, 2069) =386.04, p<0.001), however for a luminance contrast value, which depends on the vector distance, about 40%, the response becomes independent of the noise, the luminance information prevails (Current effect: F (37, 12032) = 25.846, p<0.001).Conclusão:Conclusion. The chromatic noise delayed the reaction time for luminance discrimination task in intermediate to low luminance contrast.Apoio Financeiro:IBRO short-stay grating 2016. CAPES. CNPq