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Abstract #17096 Published in IGR 9-1
A cortical pooling model of spatial summation for perimetric stimuli
Pan F; Swanson WHJournal of Vision 2006; 6: 1159-1171
Contemporary models of perimetric sensitivity assume probability summation of retinal ganglion cell sensitivities, ignoring cortical processing. To assess the role of cortical processing in perimetric spatial summation, we used a common form of multiple-mechanism spatial vision model in which the stimulus is sampled by receptive fields analogous to those of simple cells in primary visual cortex. Psychophysical threshold was computed by probability summation across the receptive fields. When the receptive fields were nonoriented (like ganglion cells), the spatial summation function had a large nonmonotonic transitional region that was inconsistent with perimetric spatial summation data. When the receptive fields were orientation tuned (like cortical cells), the model was able to give good fits to perimetric spatial summation data. The predictions of the model were evaluated with a masking study, in which noise masks either enlarged the critical area or changed the shape of the spatial summation functions. We conclude that cortical pooling by multiple spatial mechanisms can account for perimetric spatial summation, whereas probability summation across ganglion cells cannot.
Dr. F. Pan, Glaucoma Institute, State University of New York, State College of Optometry, New York, NY, USA. fpan_mail@yahoo.com
Classification:
6.6.2 Automated (Part of: 6 Clinical examination methods > 6.6 Visual field examination and other visual function tests)