#!/lusr/bin/php Demos: Computational Maps in the Visual Cortex
    Computational Maps in the Visual Cortex
     Demo 13.10
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Demo 13.10. Contour segmentation process. This animated version of Figure 13.10 shows how the neurons in the PGLISSOM orientation map synchronize and desynchronize their spiking activity to represent different contours. The input presented to the network is shown in gray-scale coding at left, the areas of the map that respond to the different input elements are delineated with circles in the middle, and the neural spiking in the 54 × 54 GMAP is shown as black and white dots at right (black means the neuron is spiking at the current time step, white means that it is not spiking). Each contour was composed of three contour elements (numbered 1, 2, 3 and 4, 5, 6), embedded in a background of three randomly oriented elements.

PGLISSOM performs contour integration through synchronized and desynchronized neural activation: Neurons that represent elements of the same contour spike at the same time, and those that represent elements in different contours spike at different times. Through self-organization, principles of good continuation and proximity have become encoded in the excitatory lateral connections, i.e. neurons that represent collinear or co-circular paths tend to be connected. The lateral connections mediate synchronization, and as a result, PGLISSOM groups collinear and co-circular elements together into continuous contours.

The neurons representing each contour quickly synchronize their activity. On the other hand, the neurons representing elements in different contours, of elements in the background, and of contour and background elements become desynchronized. In other words, the three areas representing the same contour fire together while the areas responding to the other contour and to the background are silent. (The grouping is most visible when the animation is speeded up to 0 delay). Such an alternating activation of neuronal groups ensures that each coherent object is represented distinctly and not mixed with representations of other objects.

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