[sradman]

TL;DR: during lucid REM sleep, patients with extra EEG probes around the eye socket can make detectable left to right eye movements that can be repeated to communicate numerical values (e.g. 2) in response to verbal questions like “eight minus six”.

[MasterScrat]

Note that the fact that you can communicate during LDs through eye movements has been known and used for decades already.

[WalterGR]

The dreamer has indeed been able to signal to instrumentation via eye movements during lucid dreaming for some time. Do you have any links about two-way communication being used for decades?

[sriku]

Yeah .. and a dialog my wife pokes fun at -

Me: (snoozing/dreaming) what's behind my head?

Wife: A pillow.

Me: Oh! I thought it was a spaceship.