Lateral inhibition

In neurobiology, lateral inhibition is the capacity of an excited neuron to reduce the activity of its neighbors. Lateral inhibition disables the spreading of action potentials from excited neurons to neighboring neurons in the lateral direction. This creates a contrast in stimulation that allows increased sensory perception. It is also referred to as lateral antagonism and occurs primarily in visual processes, but also in tactile, auditory, and even olfactory processing. Cells that utilize lateral inhibition appear primarily in the cerebral cortex and thalamus and make up lateral inhibitory networks (LINs). 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 is 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. This phenomenon is thought to aid in colour discrimination.

The concept of neural inhibition (in motor systems) was well known to Descartes and his contemporaries. Sensory inhibition in vision was inferred by Ernst Mach in 1865 as depicted in his mach band. Inhibition in single sensory neurons was discovered and investigated starting in 1949 by Haldan K. Hartline when he used logarithms to express the effect of Ganglion receptive fields. His algorithms also help explain the experiment conducted by David H. Hubel and Torsten Wiesel that expressed a variation of sensory processing, including lateral inhibition, within different species.

In 1956, Hartline revisited this concept of lateral inhibition in horseshoe crab (Limulus polyphemus) eyes, during an experiment conducted with the aid of Henry G Wagner and Floyd Ratliff. Hartline explored the anatomy of ommatidia in the horseshoe crab because of their similar function and physiological anatomy to photoreceptors in the human eye. Also, they are much larger than photoreceptors in humans, which would make them much easier to observe and record. Hartline contrasted the response signal of the ommatidium when a single concentrated beam of light was directed at one receptor unit as opposed to three surrounding units. He further supported his theory of lateral inhibition as the response signal of one unit was stronger when the surrounding units were not exposed to light.

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