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Lateral inhibition is defined as the process by which one cell inhibits the activity of adjacent cells . In the case of the nervous system, the cells are the neurons. The lateral inhibition of neurons generates a decrease in the activity of a group of neurons, which allows the brain to modulate the management of the information it receives from the organism’s environment. This results in the attenuation of the impact of some sensory stimuli and the optimization of the registration of other stimuli, with which lateral inhibition helps to sharpen the sensory perception of sight, hearing, touch and smell.
Neurons are the cells of the nervous system that send, receive, and interpret information from all parts of the body . It was the Spanish scientist Santiago Ramón y Cajal, Nobel Prize in Medicine, who at the end of the 19th century identified neurons as the basic structural components of the nervous system and proposed a model to explain their functioning. The main components of a neuron, whose detailed structure is shown in the figure above, are the cell body, axons, and dendrites. Dendrites extend from the neuron and receive signals from other neurons; the cell body is the processing center of a neuron, and axons are nerve extensions that branch at their terminal ends to transmit signals to other neurons.
Neurons communicate information through nerve impulses, which are action potentials, that is, waves of electrical charge that travel along the cell membrane and are transmitted by modifying the charge distribution. Nerve impulses are received in the dendrites of neurons, pass through the cell body and are carried along the axon to the terminal branches. Neurons do not touch each other, but are separated by a gap called the synaptic cleft; Signals are transmitted from one neuron, the presynaptic, to another neuron, the postsynaptic, by certain molecules, chemical messengers, called neurotransmitters . Through the synapse, a neuron can have connections with thousands of other neurons simultaneously, creating a vast neural network.
Lateral inhibition
Due to lateral inhibition, some neurons have a different level of stimulation than adjacent neurons. The main neuron in a process, the one with the highest level of stimulation, releases neurotransmitters that excite a series of neurons, following a certain sequence. At the same time, the main neuron activates neurons in the brain that inhibit the activity of other neurons located laterally to the sequence of the process. These inhibitory neurons are the nerve cells involved in communication between the central nervous system and motor or sensory neurons. In this way a contrast is created between the different stimuli, which allows the nervous system to focus or “concentrate” on a certain stimulus. As mentioned at the beginning,
Lateral inhibition of visual sensory system
In retinal cells, lateral inhibition results in edge enhancement and increased contrast in images formed in the brain. The effect of this lateral inhibition was discovered by Ernst Mach, who in 1865 explained the visual illusion called March bands.. This effect causes panels casting different shades placed side by side to appear lighter or darker at transitions, despite the uniform color within a panel. Panels appear lighter at the edge with a darker panel, and darker at the edge with a lighter panel. The darker and lighter bands at the transitions are not real, but the result of lateral inhibition. Retinal neurons that receive greater stimulation inhibit adjacent neurons to a greater degree than cells that receive less intense stimulation. Light receptors that receive information from the lighter side of the edges produce a stronger visual response than receptors that receive information from the darker side. This response from the nervous system enhances contrast at the edges,
Simultaneous contrast is also the result of lateral inhibition. In a simultaneous contrast situation, the brightness of a background affects the perception of the brightness of the main stimulus. The same main stimulus looks lighter on a dark background, and darker on a lighter background.
Lateral inhibition of tactile sensory system
Lateral inhibition also acts on touch. Perception through touch occurs through the activation of neural receptors located in the skin, which detect the pressure exerted on that surface of the body. Lateral inhibition enhances the contrast between the strongest and weakest tactile signals. Receptors that receive the strongest signals, those that occur at a point of contact, inhibit adjacent receptors to a greater extent than receptors that receive a weaker stimulus, at sites peripheral to the point of contact. This improves the sensitivity of touch perception by allowing the brain to determine the exact location of the stimulus. The areas of the body that are most sensitive to touch, such as the fingertips and tongue,
Lateral inhibition of auditory sensory system
Lateral inhibition is believed to play a relevant role in the processes associated with hearing and the conduction of information to the brain. Auditory signals travel from the cochlea in the inner ear to the auditory cortex in the temporal lobes of the brain. The different cells associated with auditory processes respond more effectively to sounds of certain frequencies. Auditory neurons that are more stimulated by sounds at a certain frequency can inhibit the action of other neurons that are less stimulated by sounds at a different frequency. This proportional inhibition of the stimulation helps to improve the contrast, and therefore the sensitivity in the perception of sound.
Sources
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