Purchase this article with an account.
Erwin Wong, Jenna Kryder; Dichoptic and monoptic spatial integration of second-order contrast. Journal of Vision 2009;9(8):1016. doi: 10.1167/9.8.1016.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Purpose. Past flanking studies using monocular viewing suggest that the second-stage neurons understood to encode second-order contrast receive substantial binocular input (Wong et al., 2005, Mansouri et al., 2005). Here we investigate the binocular nature of second-order processing more directly by using a flanking paradigm under dichoptic and monoptic viewing.
Methods. Four normal adults and one non-binocular/non-amblyopic (NBNA) adult participated. Observers detected an amplitude-modulated sinusoid alone (carrier 8 c/deg @ 3× contrast detection threshold (CDT), envelope 1 c/deg, σ = 1.5λ, 2° diameter patch, sinusoids vertical) and with two vertically aligned flanks (6' edge separation or 0.5° overlap). Flanks consisted of the target sinusoids, normalized carrier (3× CDT) and envelope (1.5× and 2.5× CDT) contrast, and were vertical, horizontal or carrier-only (control). Flanks were presented monoptically and dichoptically. Stimuli were presented via CRT and 2-AFC paradigm (500 msec intervals) with the MOCS, and viewed through a mirror haploscope with septum.
Results. For normal observers, on average the near-abutting oriented flanks facilitated contrast detection, slightly greater under monoptic than dichoptic viewing, and was contrast dependent (2.5× CTU produced greater facilitation). Dichoptic presentation of all oriented flanks overlapping the target produced suppression of contrast detection. For all views the carrier-only flanks produced no effect. For the NBNA observer, under monoptic and dichoptic viewing, the near-abutting oriented flanks at 1.5× CDT generally produced no effect and at 2.5× CDT produced suppression. Dichoptic presentation of all oriented flanks overlapping the target produced suppression. For all views the carrier-only flanks generally produced suppression.
Conclusions. Second-order contrast is substantially integrated interocularly across space but less than uniocular integration. Interocular integration was not shown by the non-binocular, non-amblyopic observer. The distinct binocular nature of second-order processing is supported by findings of non-integration of interocular first-order contrast across space (Huang et al., 2006).
This PDF is available to Subscribers Only