Chromatic spatial contrast sensitivity estimated by visual evoked cortical potential and psychophysics

Autor(es)

Barboni, M. T. S. ^[1] ; Gomes, B. D. ^[2] ; Souza, G. S. ^{[2, 3]} ; Rodrigues, A. R. ^[3] ; Ventura, D. F. ^[1] ; Silveira, L. C. L. ^{[2, 3]}

Afiliação do(s) autor(es)

^[1] Univ Sao Paulo, Inst Psicol, Sao Paulo - Brazil

^[2] Fed Univ Para, Inst Ciencias Biol, BR-66075110 Belem, Para - Brazil

^[3] Fed Univ Para, Nucleo Med Trop, BR-66075110 Belem, Para - Brazil

• Tipo de documento: Artigo Científico
• Fonte: Brazilian Journal of Medical and Biological Research; v. 46, n. 2, p. 154-163, FEB 2013.
• Citações Web of Science: 3

Resumo

The purpose of the present study was to measure contrast sensitivity to equiluminant gratings using steady-state visual evoked cortical potential (ssVECP) and psychophysics. Six healthy volunteers were evaluated with ssVECPs and psychophysics. The visual stimuli were red-green or blue-yellow horizontal sinusoidal gratings, 5° × 5°, 34.3 cd/m2 mean luminance, presented at 6 Hz. Eight spatial frequencies from 0.2 to 8 cpd were used, each presented at 8 contrast levels. Contrast threshold was obtained by extrapolating second harmonic amplitude values to zero. Psychophysical contrast thresholds were measured using stimuli at 6 Hz and static presentation. Contrast sensitivity was calculated as the inverse function of the pooled cone contrast threshold. ssVECP and both psychophysical contrast sensitivity functions (CSFs) were low-pass functions for red-green gratings. For electrophysiology, the highest contrast sensitivity values were found at 0.4 cpd (1.95 ± 0.15). ssVECP CSF was similar to dynamic psychophysical CSF, while static CSF had higher values ranging from 0.4 to 6 cpd (P < 0.05, ANOVA). Blue-yellow chromatic functions showed no specific tuning shape; however, at high spatial frequencies the evoked potentials showed higher contrast sensitivity than the psychophysical methods (P < 0.05, ANOVA). Evoked potentials can be used reliably to evaluate chromatic red-green CSFs in agreement with psychophysical thresholds, mainly if the same temporal properties are applied to the stimulus. For blue-yellow CSF, correlation between electrophysiology and psychophysics was poor at high spatial frequency, possibly due to a greater effect of chromatic aberration on this kind of stimulus. (AU)

• Processo FAPESP: 07/55125-1 - Avaliação eletrofisiológica e psicofísica das vias visuais on e off em jovens com Distrofia Muscular de Duchenne
• Beneficiário: Mirella Telles Salgueiro Barboni
• Modalidade de apoio: Bolsas no Brasil - Doutorado