Unconditioned Reflex (An unconditioned reflex is an inborn species)

UNCONDITIONED REFLEX, STIMULUS. An unconditioned reflex is an inborn species reflex that occurs without the involvement of the cerebral cortex, through excitation of lower parts of the central nervous system; examples: withdrawal of a paw in a dog deprived of the cerebral cortex in response to electrical stimulation; secretion of saliva when the mucous membrane of the oral cavity is irritated by food, etc. Academician I.P. Pavlov also classifies instincts (see) as unconditioned reflexes, considering that the latter differ only in the greater complexity of the neural mechanisms involved. The animal's response reaction to an unconditioned stimulus is characterized by strict specificity, despite the fact that the reflex can occur without the involvement of the cerebral cortex. For example, in a dog without cerebral hemispheres, different amounts of saliva of varying composition are secreted in response to different types of food. Strict specificity of the response reaction to an unconditioned stimulus is also observed in other unconditioned reflexes (defensive, orienting). See also Conditioned reflexes.