Involves

Moment

Switching on the cortex

Northwestern University, the laboratory of Horace Magoun with visiting physiologist Giuseppe Moruzzi, 1949

In 1949, Giuseppe Moruzzi and Horace Magoun published experiments in which they electrically stimulated the reticular formation in the brainstems of anesthetized cats. The stimulation transformed the animal's brain waves from the slow rhythm of sleep to the fast, low-voltage pattern of an alert, waking brain. They had found an ascending system that actively switches the cortex on: the ascending reticular activating system.

Published
1949
Stimulus
Brainstem reticular formation
Effect
Sleep to waking

The caveat

Later research showed arousal is not the work of a single homogeneous “system” but of several interacting neurotransmitter pathways; the 1949 model was the first sketch, since substantially refined and complicated.

Before this, the brainstem was seen mainly as a bundle of relay and reflex circuits. Moruzzi and Magoun's result reframed consciousness itself as something maintained by a specific, identifiable network. Failure of that network could explain coma, and its rhythms underlie the daily cycle of sleep and waking. It became one of the foundational experiments of modern neuroscience of consciousness.

The word “activating” in the system's name comes straight from this experiment. The network was defined by what it did: activate the cortex.

How it connects

The experiment that turned a tangle of brainstem neurons into the master switch of wakefulness.

This moment appeared in Attention is filtered before it is conscious, the Involves connection for August 28, 2026, which asked: Why do you suddenly notice a word everywhere the day after you learn it?

Check yourself

What did Moruzzi and Magoun demonstrate in 1949?

Electrically stimulating the brainstem reticular formation shifted the brain from a sleeping to a waking pattern.. Right. Stimulation flipped the EEG from slow sleep waves to the fast pattern of an alert brain: arousal on demand.

What the sources establish

  • Moruzzi and Magoun's 1949 paper showed that stimulation of the brainstem reticular formation produced EEG activation characteristic of the waking state.

Sources