Formation of conditioned reflexes
For the formation of a conditioned reflex, it is necessary that the conditioned stimulus first act, and then the unconditioned one. After several repetitions of this combination of stimuli in the brain, a temporary connection is established between the two foci of excitation. As a result, the action of one conditioned stimulus causes excitation in two centers.
Conditioned reflexes are formed on the basis of unconditioned reflexes and are developed with the direct participation of the cerebral cortex.
The study of the formation of conditioned reflexes was carried out in the laboratory of I.P. Pavlov in experiments on animals (dogs).
When the dog was given food (an unconditioned stimulus), it reflexively salivated – an unconditioned salivary reflex arose.
Nerve impulses arising from irritation of receptors in the tongue and in the mucous membrane of the mouth with food substances enter the center of salivation of the medulla oblongata through sensitive neurons. From here, excitation through efferent (motor) neurons is transmitted to the salivary glands, and they begin to secrete saliva. This is the arc of the unconditioned salivary reflex.
The conditioned salivary reflex was formed in dogs by a combination of feeding and lighting a light bulb or the sound of a bell.
To develop a conditioned reflex, half a minute before feeding, a light bulb or other stimulus that was indifferent to the salivary reflex was turned on. After several combinations of turning on the light bulb with feeding, a single flash of light caused salivation even if there was no food in the feeder.
As a result, after several repetitions, saliva was released in response to the action of an unconditioned stimulus (a flash of light or the sound of a bell became a signal for the appearance of food – a conditioned stimulus). This meant that a new, temporary connection was formed in the cerebral cortex between the centers of salivation and the visual (auditory), i.e., a conditioned salivary reflex was developed.
Reflexes acquired by the body during life and formed as a result of a combination of indifferent stimuli with unconditioned, I.P. Pavlov called conditioned reflexes.
Inhibition of reflexes
The conditioned reflex will be strong if the conditioned stimulus is constantly reinforced by the unconditioned one. If the conditioned stimulus is not reinforced several times, the response weakens and then becomes inhibited. The conditioned reflex does not disappear in this case. If the experiment is repeated after a break, it is restored.
A new stimulus causes an orientation reflex, therefore reflexes (both conditioned and unconditioned) are inhibited by the action of any unfamiliar stimulus (activity is terminated and the assessment of what the new stimulus is for the body: useful, harmful, or simply indifferent). Thus, with the help of the formation of conditioned reflexes and their inhibition, a more flexible adaptation of the organism to specific conditions of existence is carried out.
Inhibition can be both conditional and unconditional (external).
Example: examples of conditional inhibition – without sufficient practice, a foreign language is forgotten, a poem once learned, the ability to skate, etc.
An example of unconditioned inhibition would be an attack by a dog that is being robbed of food. In the digestive center, external unconditioned inhibition occurs, and in the center of “aggression” – excitement.