In 1949, moruzzi and magoun severed a cat's from higher brain regions; the cat lapsed into a permanent coma.

The answer is that Moruzzi and Magoun severed a cat's reticular formation system from higher brain regions and it lapsed into a permanent coma.

Explanation:

Giuseppe Moruzzi (an italian neurophysiologist) and Horace Winchell Magoun (an american neuroscientist) were brain researchers. They did the first important postwar research collaboration in sleep and waking in 1949 in the state of Chicago.

In their study, they used cats. The cats were surgically prepared using a general anesthetic or the encéphale isolé preparation.

They identified the brain center responsible for the state of sleep and found out that:

1. The stimulation of certain part of the brainstem created a state of alertness and caused the awakening of the cat from normal sleep.

2. The destruction of the central part of the brainstem made the cat fall into a permanent coma state due to an absence of wakefulness.

From these facts, they developed the concept of reticular formation system which is a complex structure that contains a cluster of neurons along with many ascending and descending nerve tracts that connects them.  

This new hypothesis was an important step to understand the physiology of wakefulness and sleep and to explain the pathophysiological bases of diseases characterized by insomnia, hypersomnia or coma as it allowed to understand things such as: why extensive damage to the brainstem can cause a permanent coma state, why barbiturates can induce sleep and narcosis, why a hit in the neck can make us lose consciousness.

This is the reason why the Moruzzi and Magoun experiment reframed science's conception of sleep as an active process that was actively controlled by the brain rather than a passive one.