Resumo

SIMAS, M.L.B.  e  SANTOS, N.A.. Contrast sensitivity to radial frequencies modulated by J_n and j_n Bessel profiles. Braz J Med Biol Res [online]. 2002, vol.35, n.11, pp. 1357-1366. ISSN 1414-431X.  http://dx.doi.org/10.1590/S0100-879X2002001100014.

We measured human contrast sensitivity to radial frequencies modulated by cylindrical (J_o) and spherical (j_o) Bessel profiles. We also measured responses to profiles of j_o, j₁, j₂, j₄, j₈, and j₁₆. Functions were measured three times by at least three of eight observers using a forced-choice method. The results conform to our expectations that sensitivity would be higher for cylindrical profiles. We also observed that contrast sensitivity is increased with the j_n order for n greater than zero, having distinct orderly effects at the low and high frequency ends. For n = 0, 1, 2, and 4 sensitivity tended to occur around 0.8-1.0 cpd while for n = 8 and 16 it seemed to shift gradually to 0.8-3.0 cpd. We interpret these results as being consistent with the possibility that spatial frequency processing by the human visual system can be defined a priori in terms of polar coordinates and discuss its application to study face perception.

Palavras-chave : Spatial frequency; Angular frequency; Polar gratings; Face perception; Contrast sensitivity.