In Zurich, Dr. Franz Vollenweider is studying how low does of an anesthetic called ketamine can affect the brain.

Ketamine can enhance your mood. It can give you feelings like euphoria. It changes all the sensory modalities. You can, for instance, hear a region. Or you can visualize things that you can't see, that first, you have illusions. Then maybe you have hallucinations. You can see things that do not exist in the real world.

Oh, now it's coming.

It's coming now.

Yeah, definitely. Taking off.

Are you able to close your eyes and focus on your inner experience?

On my what? Inner experience?

The challenge for any theory of consciousness is to explain how minute doses of an anesthetic can produce such distorted experiences.

Yes, everything is very different than usual. The visual effect and the audio effect, they are connected.

They're melded.

Yeah, they're melded.

Is vision more auditory experience and vice versa?

Yeah, one gives the other food. And that's it.

As I see it, the inputs from his senses would normally dominate his brain, creating a large spreading wave of nerve selectivity. The drug might weaken the signals coming from the senses, leaving a hectic jumble of smaller ripples of activity, spontaneously generated in the brain, producing hallucinations.

Movie in a movie in a movie or box in a box in a box or whatever. I had this experience like the space was controlling— my brain was controlling my brain was controlling my brain. Anyway.

Volunteers have been scanned while they're hallucinating. Over several minutes, a slight change in activity shows up in the front of the brain. But this time frame is too long. Consciousness is too fleeting for the subtle and transient changes in selectivity to be detected by this kind of approach.

We think that ketamine directly interferes with the communication between nerve cells. And on the ketamine, this communication is changed. Some communication is blocked even. And ketamine may lead to new assemblies between the nerve cells. And so that a different kind of network gets established on the ketamine that is normally not working in that way.

And according to your experiences, what you will see?

Oh, what I did today, yeah. I traveled through the galaxy.