A delirium resembling nitrogen narcosis that affects humanoids exposed to differing rates of time, which made Captain Picard laugh helplessly aboard the frozen Enterprise-D in Timescape.
Temporal narcosis is the name Deanna Troi gives to the giddy, intoxicated state produced when a person's body is caught between regions where time passes at different speeds. Its effects resemble the nitrogen narcosis known to deep-sea divers: confusion, inappropriate laughter and finally collapse.
It occurs in the Next Generation episode Timescape. Picard, Troi, Data and La Forge return in a runabout to find the Enterprise-D and a Romulan warbird suspended in a moment of nearly frozen time. They board wearing subspace isolation fields generated by modified emergency transporter armbands, which keep them in normal time.
The protection is imperfect. In main engineering Picard stares at the frozen bloom of a warp core breach, draws a smiling face in the cloud and dissolves into laughter before crying out in distress, forcing the others to take him back to the runabout to recover.