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Serge O. Dumoulin, Alyssa A. Brewer, Michal Ben-Shachar, Robert F. Dougherty, Brian A. Wandell; Distinguishing visual field map clusters: A new paradigm. Journal of Vision 2006;6(6):533. doi: https://doi.org/10.1167/6.6.533.
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© ARVO (1962-2015); The Authors (2016-present)
Introduction: Conventional visual field mapping contrasts stimuli at a series of visual field locations. Visual field map estimates identify the most effective stimulus position at each cortical location. Conventional methods (a) do not include a blank period, so that it is impossible to know whether all stimuli cause some response, and (b) summarize responses by a single variable that indicates only the most effective stimulus location. We introduce a new stimulus protocol and time-series modeling that provide additional information about cortical visual field sensitivity.
Methods: Conventional expanding ring and rotating wedge contrast stimuli were modified by inserting a time period with zero contrast (mean-luminance). The new paradigm allows us to compare contrast responses at multiple locations with a zero contrast stimulus and estimate a better spatial model of the local cortical visual field responsivity from the response time course. Besides conventional Fourier analysis, the response components were estimated using a general linear model.
Results: Cortex within V1–V3 is predominantly sensitive to stimulus location. Lateral and ventral occipital cortex respond to stimuli from a much larger part of the visual field, but is also sensitive to stimulus location. The transition between V1 and LO maps is particularly distinctive, allowing segregation of the confluent foveal regions that are otherwise hard to discern.
Discussion: The new paradigm and response modeling provide a more quantitative description of the visual field map properties. The cortical selectivity differs across visual field clusters, permitting accurate segmentation of visual field maps that are hard to distinguish with other methods.
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