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Sang-Il Kim, Randolph Blake, Sang-Hun Lee; When a traveling wave meets a gap on its way. Journal of Vision 2005;5(8):2. doi: https://doi.org/10.1167/5.8.2.
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During binocular rivalry, one sees perceptual waves in which the dominance of one pattern emerges locally and expands progressively. This intriguing phenomenon provides a tool by which the nature of cortical network can be probed by detailing the dynamics of perceptual waves, given a tight linkage between perceptual waves and cortical waves in the early visual cortex (Lee et al., 2004). Wilson et al (2001) proposed a model that wave propagation is mediated by inhibitory interactions between two layers of cells, and the efficiency of propagation is regulated by reciprocal excitatory connections within each layer. With this model in mind, we attempted to estimate the efficiency of recurrent connections by assessing how the size of a gap in patterns affects the dynamics of perceptual waves. Subjects viewed a dichoptic display of a spiral annulus and a radial annulus. When a spiral grating was dominant, the contrast pulse was applied to a small region in a radial grating, resulting in a perceptual wave of a radial pattern propagating from that region. The speed of a wave was measured by a key press when a wave arrived at a region marked by nonius lines positioned 135° away from the contrast pulse. A gap of various sizes was placed on a radial grating. Another key press indicated whether a wave propagated continuously and reached the lines allowing to estimate a threshold gap size at which the probability of waves jumping the gap was 50%. The radius of annulus patterns was varied to see how the threshold gap size is affected by the eccentricity. The threshold gap size was greater for interhemispheric waves than for intrahemispheric ones, but was constant across different eccentricities when the gap size was converted into the cortical distance on V1. The effect of gaps coincides with the known functional organization of the early visual cortex and predicts that the range or the strength of recurrent connections among neurons is homogeneous throughout the cortical surface within a given visual area.
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