Lateral Inhibition - Sensory Inhibition

Georg von Békésy, in his book Sensory Inhibition, explores a wide range of inhibitory phenomena in sensory systems, and interprets them in terms of sharpening.

When, for instance, the skin is touched by an object, several sensory neurons in the skin next to one another are stimulated. Neurons that are firing suppress the stimulation of neighbouring neurons. In the face of inhibition, only the neurons that are most stimulated and least inhibited will fire, so the firing pattern tends to concentrate at stimulus peaks.

Lateral inhibition increases the contrast and sharpness in visual response. This phenomenon occurs in the mammalian retina, for example. In the dark, a small light stimulus will be enhanced by the different photoreceptors (rod cells). The rods in the center of the stimulus will transduce the "light" signal to the brain, whereas different rods on the outside of the stimulus will send a "dark" signal to the brain. This contrast between the light and dark creates a sharper image. (Compare unsharp masking in digital processing). This mechanism also creates the Mach band visual effect.

Artificial lateral inhibition has been incorporated into artificial sensory systems, such as vision chips, hearing systems, and optical mice.

An often under-appreciated point is that although lateral inhibition is visualised in a spatial sense, it is also thought to exist in what are known as "lateral inhibition across abstract dimensions". This refers to lateral inhibition between neurons that are not adjacent in a spatial sense, but in terms of modality of stimulus, for example. This phenomenon is thought to aid in colour discrimination.