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Andrew John Anderson, Chris A. Johnson; Mechanisms Isolated by Frequency-Doubling Technology Perimetry. Invest. Ophthalmol. Vis. Sci. 2002;43(2):398-401.
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© ARVO (1962-2015); The Authors (2016-present)
The frequency-doubling (FD) phenomenon describes the increase in
apparent spatial frequency occurring when low-spatial-frequency sine
wave gratings undergo rapid counterphase flicker. It is unclear whether
the visual mechanisms isolated when pattern appearance is used as a
threshold criterion are the same as when a simple detection criterion
(as in FD perimetry) is used. It is also unclear whether the FD
stimulus isolates mechanisms that differ from those isolated by
spatially uniform flicker. In the current study, adaptation and
spatiotemporal tuning functions were determined, using the FD stimulus,
uniform flicker, and static (nonflickering) grating targets, to
establish whether distinct mechanisms are isolated by the FD stimulus.
methods. Spatiotemporal tuning functions were determined in six observers, using
an FD stimulus under conditions of detection and resolution and using
spatially uniform flickering stimuli and static grating stimuli. The
effect of light adaptation on these stimulus classes was also assessed.
All stimuli were 10°-wide squares.
results. Spatiotemporal tuning functions and adaptation characteristics were
identical for both the FD detection and resolution paradigms. Spatially
uniform flicker gave indistinguishable tuning functions and adaptation
characteristics to the FD stimulus at 25 Hz and higher, but differed
below this frequency. Static grating stimuli differed from FD stimuli
in both tuning functions and adaptation characteristics.
conclusions. Absolute detection of the FD stimulus involves mechanisms that are
indistinguishable from those involved when a criterion based on spatial
form (i.e., resolution of a pattern) is used, indicating that a simple
detection criterion can be used in FD perimetry. The FD stimulus
isolates similar mechanisms to spatially uniform flickering stimuli at
high temporal frequencies.
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