Animal Behavi24 - due to light inhibit their neighboring...

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Animal Behavior: Instinct Case Study: Toad Vision Toads, like many animals, detect their prey visually. A shape that is long in the horizontal direction looks like a worm, and so the toad's brain interprets that as food. A square shape elicits no reaction from the toad, and a tall, thin shape is seen by the toad as the "anti-worm." Figure %: Prey detection in toads How might we wire a system to detect and respond to such shapes? The optimal system (and the one that exists in animals) has lateral inhibition. But first, let's look at a system that does not have lateral inhibition. No lateral inhibition Assume that neurons fire when light hits them, and do not fire when there is no light. Edges would appear "fuzzy" because neurons near the edge of the shape's shadow would fire somewhat. Figure %: A visual system without lateral inhibition Lateral Inhibition
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Now, let's look at a system that includes lateral inhibition, a process by which neurons that fire
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Unformatted text preview: due to light inhibit their neighboring neurons. Neurons in the middle of a light-receiving area will be inhibited slightly by their neighboring neurons, which are also receiving light. However, neurons on a black/white edge fire more intensely than nearby neurons receiving exactly the same amount of light because neurons on this edge are not being inhibited by their nearest neighbors in the dark areas, which is not firing. This allows edges to be seen with greater definition. Look at a black shape against a white piece of paper. Does the white right at the edge of the shape look brighter than the rest of the paper? Well-defined shapes can be detected using complex systems based on this principle of light and dark patterns. Figure %: A visual system with lateral inhibition...
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Animal Behavi24 - due to light inhibit their neighboring...

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