Low level constraints on dynamic contour path integration

摘要

Contour integration is a fundamental visual process. The constraints on integratinguddiscrete contour elements and the associated neural mechanisms have typically beenudinvestigated using static contour paths. However, in our dynamic natural environmentudobjects and scenes vary over space and time. With the aim of investigating theudparameters affecting spatiotemporal contour path integration, we measured humanudcontrast detection performance of a briefly presented foveal target embedded inuddynamic collinear stimulus sequences (comprising five short 'predictor' bars appearingudconsecutively towards the fovea, followed by the 'target' bar) in four experiments. Theuddata showed that participants' target detection performance was relatively unchangedudwhen individual contour elements were separated by up to 2° spatial gap or 200msudtemporal gap. Randomising the luminance contrast or colour of the predictors, on theudother hand, had similar detrimental effect on grouping dynamic contour path andudsubsequent target detection performance. Randomising the orientation of theudpredictors reduced target detection performance greater than introducing misalignmentudrelative to the contour path. The results suggest that the visual system integratesuddynamic path elements to bias target detection even when the continuity of path isuddisrupted in terms of spatial (2°), temporal (200ms), colour (over 10 colours) andudluminance (-25% to 25%) information. We discuss how the findings can be largelyudreconciled within the functioning of V1 horizontal connections.