Ketamine abolishes alpha brain wave patterns and promotes theta brain wave activity.

“when people take ketamine the alpha pattern of activity is completely abolished at least for the duration of time that they're under the influence of the drug which typically is about an hour to two hours or so and a different pattern of brain activity which is called the Theta pattern of brain activity starts to really emerge it's as if it gets unveiled and that Theta pattern of activity is the one that's associated with a dreamlike state it's the one that resides more or less at that Lial border between wakefulness and sleep”