Abstract

Contour integration is a fundamental visual process. The constraints on integrating
discrete contour elements and the associated neural mechanisms have typically been
investigated using static contour paths. However, in our dynamic natural environment
objects and scenes vary over space and time. With the aim of investigating the
parameters affecting spatiotemporal contour path integration, we measured human
contrast detection performance of a briefly presented foveal target embedded in
dynamic collinear stimulus sequences (comprising five short 'predictor' bars appearing
consecutively towards the fovea, followed by the 'target' bar) in four experiments. The
data showed that participants' target detection performance was relatively unchanged
when individual contour elements were separated by up to 2° spatial gap or 200ms
temporal gap. Randomising the luminance contrast or colour of the predictors, on the
other hand, had similar detrimental effect on grouping dynamic contour path and
subsequent target detection performance. Randomising the orientation of the
predictors reduced target detection performance greater than introducing misalignment
relative to the contour path. The results suggest that the visual system integrates
dynamic path elements to bias target detection even when the continuity of path is
disrupted in terms of spatial (2°), temporal (200ms), colour (over 10 colours) and
luminance (-25% to 25%) information. We discuss how the findings can be largely
reconciled within the functioning of V1 horizontal connections.