The refutation of the brain as a reflex system was, in fact, the decisive step in the new research in neurophysiology. Hubel and Evarts carried out more systematic studies concerning the recording of individual neurons. They applied them primarily in the domain of the neurophysiology of sleep. Their investigations put a definitive end to reflex physiology, which defended the thesis that the brain is at rest during sleep. Neurobiologists have been able to identify the cerebral system that is responsible for paradoxical sleep. The controversy concerned the direct link that the investigators established between paradoxical sleep and dream formation. Diverse studies show that only a minor part of the connections of the thalamo-cortical system is concerned by sensory information, even though the system in question is responsible for states of consciousness, in waking life as in the world of dreams. The continuity between sleep and dreams, as suggested by the activation-synthesis theory, is in opposition to Freudian theory.