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Binocular contrast interactions: dichoptic masking is not a single process

Record type: Article

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.

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Citation

Baker, Daniel H. and Meese, Tim S. (2007) Binocular contrast interactions: dichoptic masking is not a single process Vision Research, 47, (24), pp. 3096-3107. (doi:10.1016/j.visres.2007.08.013).

More information

Submitted date: 30 May 2007
Published date: 25 October 2007
Keywords: dichoptic masking, grating contrast, phase, orientation, spatial frequency, binocular summation

Identifiers

Local EPrints ID: 48580
URI: http://eprints.soton.ac.uk/id/eprint/48580
ISSN: 0042-6989
PURE UUID: a346a145-5eec-49e1-b7d1-d5e6c3dd0bd1

Catalogue record

Date deposited: 01 Oct 2007
Last modified: 17 Jul 2017 14:59

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Contributors

Author: Daniel H. Baker
Author: Tim S. Meese

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