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(Reference retrieved automatically from Web of Science through information on FAPESP grant and its corresponding number as mentioned in the publication by the authors.)

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

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Author(s):
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]
Total Authors: 6
Affiliation:
[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
Total Affiliations: 3
Document type: Journal article
Source: Brazilian Journal of Medical and Biological Research; v. 46, n. 2, p. 154-163, FEB 2013.
Web of Science Citations: 3
Abstract

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)

FAPESP's process: 07/55125-1 - Electrophysiological and psychophysical evaluation of ON and OFF visual pathways in Duchenne muscular dystrophy young patients
Grantee:Mirella Telles Salgueiro Barboni
Support Opportunities: Scholarships in Brazil - Doctorate