Info

This system is illustrated in Figure 7.1-4. Note that there is a triple AND-ing of the T operator outputs. Again, it is possible to list the outputs for various inputs, stationary and moving:

Vd(A) = 0 For general ON over all n receptors in the line.

Vd(A) = 0 For general OFF over all n receptors in the line.

Vd(A) = 0 For any stationary pattern of light and dark over the line of n receptors.

Vd(A) = 0 For a light/dark boundary moving to the right at unit velocity.

Vd(A) = 0 For a dark/light boundary moving to the right at unit velocity.

Vd(A) = 0 For a light/dark boundary moving to the left at unit velocity.

Vd(A) = 0 For a dark/light boundary moving to the left at unit velocity.

Vd(A) = 0 For a light unit spot moving to the right at unit velocity.

Vd(A) = 0 For a light unit spot moving to the left at unit velocity.

Vd(A) = 0 For a dark unit spot moving to the left at unit velocity.

Vd(A) = (1111 ... 1) For a dark unit spot moving to the right at unit velocity.

Thus, Vd(A) detects only a unit dark spot moving to the right with unit velocity. Note that if one interchanges the T1 (ON) operators with the T2 (OFF) operators in Figure 7.1-4, the system detects only unit light spots moving to the right at unit velocity.

What the Zorkoczy models suggest is that spatiotemporal feature extraction, and the sensing of object velocity, may involve the systematic basic operations of OFF and ON at the single receptor level, and that these outputs are further conditioned by delays and sent to adjacent receptor processing modules where they are appropriately combined. By considering the shape of the receptor arrays (e.g., lines, areas, etc.), it is possible to extend one-dimensional Zorkoczy models to respond to two-dimensional, contrasting objects, either stationary or moving in a particular direction on the receptor array. The formal, binary Zorkoczy models are not supposed to emulate biological behavior, but instead to suggest continuous, fuzzy, nonlinear, neural configurations that might be modeled as candidates for feature extraction circuits.

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