Purchase this article with an account.
AJ Anderson, CA Johnson; Characteristics of the Spatio-temporal Mechanisms Isolated in Frequency-doubling Perimetry . Invest. Ophthalmol. Vis. Sci. 2002;43(13):2124.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Purpose: The frequency doubling (FD) phenomenon describes the increase in apparent spatial frequency occurring when low spatial frequency sinewave 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. We determined adaptation and spatio-temporal tuning functions using the FD stimulus, uniform flicker, and static (non-flickering) grating targets, to establish whether distinct mechanisms are isolated by the FD stimulus. Methods: Spatio-temporal tuning functions were determined for six observers using a FD stimulus under conditions of detection and pattern resolution, as well as for 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, presented either centrally or at 15 eccentricity. Results: Spatio-temporal 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 above, but differed below this frequency. Static grating stimuli differed from FD stimuli in both tuning functions and adaptation characteristics. Conclusion: 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.
This PDF is available to Subscribers Only