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Tim S. Meese, Daniel H. Baker, Robert J. Summers, Mark A. Georgeson; Contrast integration and counter suppression: a general scheme for visual hierarchies?. Journal of Vision 2012;12(14):33. doi: 10.1167/12.14.33.
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© ARVO (1962-2015); The Authors (2016-present)
Low contrast stimuli are much easier to detect with two eyes than with one, suggesting a process of signal summation. But in everyday life, when we close one eye, the contrast of the world does not diminish, but remains fairly constant implying that different or additional processes are involved above threshold. We have developed a generic gain control model of contrast summation that involves contrast integration along the dimension of interest and slightly less potent suppression along the same dimension: the model giveth with one hand and taketh away with the other. This counter intuitive behavior allows the model to benefit from pooling at threshold, yet maintain a contrast code that is invariant with the extent of pooling above threshold. It also suggests that it might be possible to reveal the operation of the integration process above threshold with appropriate experimental manipulations. By measuring various forms of 'dipper functions' we have been able to confirm this in the domains of: ocularity, space, orientation and time. The model also predicts paradoxical psychometric functions ('swan' functions) that we find for appropriate arrangements of target and pedestal in each of the same four dimensions. Furthermore, we show that the general arrangement that we propose is a suitable basis for building visual hierarchies and population codes for global measures along various dimensions of interest. This idea receives some direct support from novel experiments in which we reveal aftereffects for global size adaptation.
Meeting abstract presented at OSA Fall Vision 2012
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