ABSTRACT
The aim of this study was to assess contrast sensitivity for angular frequency stimuli as well as for sine-wave gratings in adults under the effect of acute ingestion of alcohol. We measured the contrast sensitivity function (CSF) for gratings of 0.25, 1.25, 2.5, 4, 10, and 20 cycles per degree of visual angle (cpd) as well as for angular frequency stimuli of 1, 2, 4, 24, 48, and 96 cycles/360°. Twenty adults free of ocular diseases, with normal or corrected-to-normal visual acuity, and no history of alcoholism were enrolled in two experimental groups: 1) no alcohol intake (control group) and 2) alcohol ingestion (experimental group). The average concentration of alcohol in the experimental group was set to about 0.08%. We used a paradigm involving a forced-choice method. Maximum sensitivity to contrast for sine-wave gratings in the two groups occurred at 4 cpd sine-wave gratings and at 24 and 48 cycles/360° for angular frequency stimuli. Significant changes in contrast sensitivity were observed after alcohol intake compared with the control condition at spatial frequency of 4 cpd and 1, 24, and 48 cycles/360° for angular frequency stimuli. Alcohol intake seems to affect the processing of sine-wave gratings at maximum sensitivity and at the low and high frequency ends for angular frequency stimuli, both under photopic luminance conditions.
Subject(s)
Adult , Female , Humans , Male , Young Adult , Alcohol Drinking/physiopathology , Alcohol Drinking/psychology , Contrast Sensitivity/drug effects , Fourier Analysis , Color Vision/drug effects , Ethanol/analysis , Psychophysics/methods , Review Literature as Topic , Size Perception , Task Performance and Analysis , Visual Acuity , Visual Perception/drug effectsABSTRACT
O objetivo deste trabalho foi mensurar curvas de resposta ao contraste para os filtros de freqüências angulares de banda estreita de 32, 48, 64 e 96 ciclos/360º. Foram estimadas nove curvas para cada filtro com o método psicofísico de somação de resposta de supralimiar aliado ao método da escolha forçada. Participaram deste experimento seis participantes adultos com acuidade visual normal ou corrigida. Os resultados demonstraram somações máximas de limiar de contraste na freqüência de teste dos filtros de 32, 48, 64 e 96 ciclos/360º circundadas por inibições nas freqüências vizinhas às freqüências angulares de teste de cada filtro. Estes resultados são consistentes com a existência de filtros de freqüências angulares de banda estreita no sistema visual humano através do processo de somação ou inibição na faixa de freqüência angular alta.
The aim of this study was to measure narrow-band frequency response curves for four angular frequency filters. The test frequencies were 32, 48, 64 and 96 cycles/360º. Six humans observers with normal or corrected visual acuity measured nine curves for each filter, with a supra-threshold response summation psychophysical method allied with a forced-choice method. The results showed maximum summation effects at test frequency for filter frequencies 32, 48, 64 and 96 cycles/360º, as well as a strong inhibition for neighboring frequencies. These results are consistent with the existence of narrow-band angular frequency filters in the human visual system either through summation or the inhibition of specific high angular frequency ranges.