Fields of Gabor patches are often used to investigate psychophysically contextual effects thought to result from lateral interactions in the early visual cortical areas. Contour integration is one of those tasks that promote figure-ground segregation based on several Gestalt principles such as proximity, similarity, good continuation and closure. The precise manipulation of the local properties can help study how global processing emerges from the integration of local features in the visual cortex.

References:

  Field et al (1993) Contour integration by the human visual system: evidence for a local “association field". Vision Research 33:173–193

  Geisler et al (2001) Edge co-occurrence in natural images predicts contour grouping performance. Vision Research 41:711–724

  Beaudot & Mullen (2003) How long range is contour integration in human color vision?. Visual Neuroscience 20(1):51–64

Here is the math behind the basic element of this contrast-defined stimulus:
  
    xrot = x*cos(angle)-y*sin(angle)
    carrier = sin(2*pi*sf*xrot)
    envelope = exp(-(r*r)/(2*sigma*sigma))
    z = carrier*envelope
  

This element is then replicated at different positions (x_i, y_i) and modified according to:

  nbrc = 10; shift = (nbrc-1)/2; sep = sigma*10
  for i = 0 : 99
    x_i = (floor(i/nbrc)-shift)*sep
    y_i = (mod(i,nbrc)-shift)*sep
    angle = (100-coherence)*atan2(y_i ,x_i )/10
    

The whole stimulus is generated in real-time using a GLSL shader that runs right inside your WebGL-compatible browser. The plain Math behind the stimulus was converted to this optimized GLSL shader using the new Psykinematix Pro Edition. Translation to Matlab and Python code is also possible !

This whole widget was also fully generated using Psykinematix Pro Edition. The parameters that control the stimulus properties through the sliders are the same as the ones you would define as dependent or independent variables when using the stimulus in an actual psychophysical experiment run in Psykinematix. The widget creation is otherwise fully customizable with your own logo, copyright, links, etc.

To learn more about the widget creation, click on the above "Made With" button !