Binocular contrast interactions: dichoptic masking is not a single process
Baker, Daniel H. and Meese, Tim S. (2007) Binocular contrast interactions: dichoptic masking is not a single process. Vision Research, 47, (24), 3096-3107. (doi:10.1016/j.visres.2007.08.013).
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To decouple interocular suppression and binocular summation we varied the relative phase of mask and target in a 2IFC contrast-masking paradigm. In Experiment I, dichoptic mask gratings had the same orientation and spatial frequency as the target. For in-phase masking, suppression was strong (a log-log slope of ~1) and there was weak facilitation at low mask contrasts. Anti-phase masking was weaker (a log-log slope of ~0.7) and there was no facilitation. A two-stage model of contrast gain control (Meese, Georgeson and Baker, 2006, J. Vis, 6: 1224-1243) provided a good fit to the in-phase results and fixed its free parameters. It made successful predictions (with no free parameters) for the anti-phase results when (A) interocular suppression was phase-indifferent but (B) binocular summation was phase sensitive. Experiments II and III showed that interocular suppression comprised two components: (i) a tuned effect with an orientation bandwidth of ~±33° and a spatial frequency bandwidth of >3 octaves, and (ii) an untuned effect that elevated threshold by a factor of between 2 and 4. Operationally, binocular summation was more tightly tuned, having an orientation bandwidth of ~±8°, and a spatial frequency bandwidth of ~0.5 octaves. Our results replicate the unusual shapes of the in-phase dichoptic tuning functions reported by Legge (1979, Vis Res, 69: 838-847). These can now be seen as the envelope of the direct effects from interocular suppression and the indirect effect from binocular summation, which contaminates the signal channel with a mask that has been suppressed by the target.
|Keywords:||dichoptic masking, grating contrast, phase, orientation, spatial frequency, binocular summation|
|Subjects:||R Medicine > RE Ophthalmology
B Philosophy. Psychology. Religion > BF Psychology
|Divisions:||University Structure - Pre August 2011 > School of Psychology
|Date Deposited:||01 Oct 2007|
|Last Modified:||06 Aug 2015 02:39|
|RDF:||RDF+N-Triples, RDF+N3, RDF+XML, Browse.|
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