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Robert F. Hess, Pi-Chun Huang; Suppression Has Different Sustained And Transient Components. Invest. Ophthalmol. Vis. Sci. 2012;53(14):3901.
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Suppression was measured in a group of amblyopic observers using a modified dichoptic probed-sinewave paradigm.
A briefly presented (16.6ms) letter was presented dichoptically on a sinusoidally flickering mask. The detection threshold of the letter was measured in the amblyopic eye at various phases with respect to the flickering mask presented to the fixing eye. Three flickering frequencies (1, 2, 3 Hz) and four different types of masks were used: (1) large uniform field of luminance (2) large field of contrast noise with a 1/f power spectrum (3) localized contrast mask covering only the area of the letter (4) surround contrast mask which is equal to (2)-(3).
The results showed that luminance stimuli seen by the fixing eye generally increased the detecting threshold in a sustained fashion, but no more than expected of normal vision. Contrast stimuli seen by the fixing eye [2, 3, 4], on the other hand, induced both a sustained and transient (i.e. modulated) suppression of the amblyopic eye. Unlike the sustained component, the modulated component was present for surround stimuli seen by the fixing eye but absent for localized, overlay stimuli.
Our results suggest that amblyopic suppression is characterized by both a sustained component and a transient component that operates via surround inhibitory processes.
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