Purchase this article with an account.
Patrick Schiller, Nicole Anderson; Differences in the Role of Context on Polar and Translational Glass Patterns. Journal of Vision 2011;11(11):1105. doi: 10.1167/11.11.1105.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Thresholds for stimuli that rely upon activity from early visual mechanisms can be modulated by contextual information. In the orientation domain, for example, thresholds for targets that are surrounded by parallel elements are typically higher than thresholds for targets that are surrounded by orthogonal or grey surrounds. These behavioural results are thought to reflect inhibitory interactions between neurons that are tuned to similar stimulus properties. In the current study, we evaluated whether the same contextual effects would be observed with stimuli that probe mid-level form mechanisms. Coherence thresholds were evaluated for polar (ie., concentric and radial) and translational (ie., vertical and horizontal) Glass stimuli using the method of constant stimuli and a 2IFC paradigm. Baseline coherence thresholds were first determined for stimuli with no surround (radius = 1.25°: dot density = 12%), where subjects discriminated Glass patterns from noise with no coherent form. Thresholds were then determined when stimuli were surrounded by a pattern that was either the same as, or different from, the central pattern. With translational stimuli, thresholds for all 4 subjects were higher with the same surround than they were with a different surround. With polar stimuli, thresholds for 3 subjects were lower with the same surround than they were with a different surround (for one subject, polar thresholds did not differ between the 2 surround conditions). This demonstrates that the role of the surround on translational form perception is qualitatively different from the role of the surround on polar form perception for the stimulus parameters we have chosen here. We propose that this difference can be explained in terms of differences in the extent of spatial pooling that occurs between early vs. mid-level visual neural mechanisms.
This PDF is available to Subscribers Only