Spatial integration within and between first- and second-order stimuli

R. Summers, D.H. Baker, T. Meese

Research output: Contribution to journalConference abstractpeer-review


The detection of first-order (luminance-modulated—LM) and second-order (contrast-modulated—CM) stimuli is believed to involve separate mechanisms that interact weakly or are entirely independent; detection of an LM-only stimulus is barely improved by the addition of CM. However, little is known about the integration of stimuli comprising non-overlapping regions of LM and CM. Spatial summation of LM, CM and LM+CM targets was assessed using (i) full 1.25 c deg -1gratings of different sizes (1–16 cycles), (ii) fixed-diameter targets whose signal area was controlled by modulating a large (8 or 16 cycles) ‘full’ grating with a raised plaid pattern. The noise carrier (also present for LM stimuli) was bandpass-filtered white noise (8 c deg -1, ±0.5 octaves). We find that sensitivity improves with target size more rapidly for LM than for CM. When area was constant, comparing full and modulated stimuli yielded summation of ∼5dB for both CM and LM. We also investigated cross-order summation, which was weak (∼2dB) for full CM+LM (threshold adjusted) stimuli, but stronger (∼3dB) when first and second order stimuli were interdigitated over area. This suggests a mechanism capable of integrating textures with attributes that vary over space, perhaps owing to changes in illumination or material properties.
Original languageEnglish
Article number153
Pages (from-to)223
Number of pages1
Issue numberSuppl.1
Publication statusPublished - Sept 2012
Event35th European Conference on Visual Perception - Alghero, Italy
Duration: 2 Sept 20126 Sept 2012

Bibliographical note

ECVP 2012 Abstracts


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