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Separate first- and second-order processing is supported by spatial summation estimates at the fovea and eccentrically.

Sukumar S, Waugh SJ

University of Manchester, Department of Ophthalmology, Manchester Royal Eye Hospital, Oxford Road, M13 9WH, UK; Anglia Vision Research, Department of Optometry and Ophthalmic Dispensing, Anglia Ruskin University, Cambridge CB1 1PT, UK.

We estimated spatial summation areas for the detection of luminance-modulated (LM) and contrast-modulated (CM) blobs at the fovea, 2.5, 5 and 10deg eccentrically. Gaussian profiles were added or multiplied to binary white noise to create LM and CM blob stimuli and these were used to psychophysically estimate detection thresholds and spatial summation areas. The results reveal significantly larger summation areas for detecting CM than LM blobs across eccentricity. These differences are comparable to receptive field size estimates made in V1 and V2. They support the notion that separate spatial processing occurs for the detection of LM and CM stimuli.

Published 19 February 2007 in Vision Res, 47(5): 581-96.
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