The Nobel Prize in medicine was awarded Monday to three scientists working on the mechanisms the brain uses to switch on or off the activity of individual nerve cells.

Karl Deisseroth, 54, Peter Hegemann, 71, and Georg Nagel, 73, have carried out research into light-gated ion channels and optogenetics. They are based at universities in Germany and the United States.

The Nobel committee lauded their work, writing on X that the method "is now being used in laboratories around the world to reveal the brain's mysteries."

The Nobel Assembly said Deisseroth is based at Stanford University in California, while Hegemann is at Humboldt University in Berlin and Nagel at the University of Würzburg in Germany.

Thomas Perlmann, the secretary of the medicine committee, said he was able to reach all three winners by phone Monday.

The prize was announced at the Karolinska Institute in Stockholm, kicking off Nobel week.

The prize money this year is 12 million Swedish kronor (about $1.2 million).

Last year, the prize went to three scientists researching the immune system.

Monday's medicine prize is followed by the physics prize on Tuesday, chemistry on Wednesday and literature on Thursday.

After Friday's peace prize is awarded, the Nobel Memorial Prize in Economic Sciences will be announced on Oct. 12.

The prize money this year is 12 million Swedish kronor (about $1.2 million), whether for an individual, a small group of laureates, or an organization.