Sc. Dakin et I. Mareschal, Sensitivity to contrast modulation depends on carrier spatial frequency and orientation, VISION RES, 40(3), 2000, pp. 311-329
We consider how the detection of second-order contrast structure depends on
the orientation and spatial frequency of first-order luminance structure.
For patterns composed of a bandpass noise carrier multiplied by a contrast
envelope function, we show that sensitivity to the envelope varies in propo
rtion to the spatial frequency of the carrier. For oriented carriers at low
spatial-frequencies, detection of the contrast envelope is easier when the
envelope and carrier are perpendicular, but this dependency diminishes as
the spatial frequency of the carrier increases. These differences are not a
ttributable to either the detection of side-bands, or the presence of spuri
ous contrast structure in unmodulated carrier images. A final experiment me
asured envelope detection in the presence of noise masks. Results indicate
that orientationally and spatially-band pass filtering precedes the detecti
on of second-order structure. (C) 2000 Elsevier Science Ltd. All rights res
erved.