Ivan Pavlov, answered from the texts and cited to the page.
Behind every conditioned reflex is the brain, and I could not rest content with the reflex as a mere fact of behavior; I had to understand it as a process in the cortex. I picture the cerebral cortex as a vast surface across which two nervous processes, excitation and inhibition, are continually at play — arising at points, spreading outward ("irradiating"), then drawing back and concentrating — so that the state of the higher nervous activity at any moment is the momentary pattern, the mosaic, of excitation and inhibition over the cortex.12
Inhibition is not mere absence; it is a positive process, as real as excitation, and it does the work of extinction, of differentiation, of delay — the whole negative, restraining side of the nervous life. From this I could explain what had seemed mysteries. Sleep is inhibition irradiated over the whole cortex; hypnosis is inhibition spread over part of it, leaving an island awake; the phases of transition between waking and sleep are the partial, uneven spread of the inhibitory process.3
The cortex, in short, is a dynamic thing, its excitation and inhibition forever shifting, and the laws of the conditioned reflex are the laws of that shifting made visible in the behavior of the animal.4
So we are compelled to conclude that the original excitation m the aggressive center irradiated, and also charged the food center. I shall now show you, on the other hand, a striking case of irradiation of inhibition Detailed investigations have proved that the inhibition which exists always simultaneously with excitation and controls it, is, in essence, the same process as sleep.Lectures on Conditioned Reflexes
Ob- viously, the fact which confronted the physiologist was a characteristic of the brain as a part of the central nervous system, the fact that excitation easily spreads from its original point over a large area of the cerebral cortex, the fact of irradiation of the nervous process 218 LECTURES ON CONDITIONED REFLEXES over many groups of nerve clls Tnis %rradiaUoyi of the excitation is constantly met with in the…Lectures on Conditioned Reflexes
It has, no doubt, occu o some that these two types present a contradiction to the of the identity of sleep and internal inhibition, in that the with a predisposition to excitation tends to fall asleep ngaggo conditions of our experiments, while the type with a pre sition to inhibition remains fully awake.Conditioned Reflexes
For the formation of con- NORMAL AND PATHOLOGICAL STATICS 355 ditioned reflexes we employ two unconditioned reflexes almost exclu- sively; the food reflex and the defensive reflex (the latter is seen upon introducing into the mouth of the animal "iot food but substances which the dog rejects, such as a weak solution of acid).Lectures on Conditioned Reflexes
Pavlov's most speculative extension — the reading of a detailed cortical physiology off the behavioral data of conditioning — and the part of his system most revised by later science. The twentieth-century neuroscience of the neuron, the synapse, and the localized circuit superseded Pavlov's picture of excitation and inhibition irradiating across the cortical surface, and many judged that he had inferred more about the brain than his salivary data could warrant. Yet the functional concepts survived the revision: inhibition as an active process, generalization and discrimination, the dynamic balance of excitation and restraint remain part of the vocabulary of the nervous system, and his account of sleep and hypnosis as inhibitory states influenced later work. The dispute is over how much of the cortical theory the behavioral evidence actually licensed.