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Christopher A. Henry, Michael J. Hawken; Orientation Dependence of Contextual Suppression Derived from Psychophysical Reverse-Correlation. Journal of Vision 2010;10(7):1372. https://doi.org/10.1167/10.7.1372.
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© ARVO (1962-2015); The Authors (2016-present)
The ability to detect a visual target can be affected, often quite dramatically, by the spatial context surrounding it. It is thought that the spatial summation and extra-classical receptive field (eCRF) properties of visual cortical neurons underlie this perceptual metacontrast masking. Orientation-dependent contextual effects have been reported in both perceptual masking and neurophysiology and it is natural to compare the two.
We have previously investigated the tuning properties of the eCRFs of neurons in macaque V1 (Henry et al. SFN 2008). Using a subspace reverse-correlation paradigm, we measured the temporal impulse-responses of neurons to the presentation of oriented gratings in their eCRFs. In general, the eCRF stimuli suppressed the neurons' responses, most often with the strongest suppression occurring for collinear stimuli.
Here, we measured the orientation dependence of metacontrast masking psychophysically using a similar reverse-correlation paradigm. Parafoveally presented stimuli consisted of an outer annulus – the surround – and an inner patch. A vertical near-threshold contrast grating target was briefly (24 ms) and randomly presented in the inner patch at a rate of 2 Hz. A continuous sequence of gratings was presented in the outer annulus (18 total orientations, changing every 24 ms). During 1 minute blocks subjects were instructed to press a key when they detected a target grating.
Analysis consisted of correlating the randomly-presented stimuli in the outer annulus with subjects' key presses, as we did with neuronal spiking in the previous study. Subjects were less likely to detect the targets in the presence of oriented surrounds, with the most masking coming from collinear stimuli. Moreover, the orientation bandwidth of the masking effect is similar to the bandwidth measured for neuronal eCRFs. Thus, using similar approaches, we have shown that masking effects in human behavior are similar to eCRF suppression observed in macaque V1.
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