Ability to talk only in dreams?

[Daniel Riaño]

I am puzzled by this case. Two years ago, the son of an acquaintance of
mine, who was a perfectly normal and healthy 16 years old kid, suffered an
ictus, and he has been at the hospital all this time, under professional
care, unable to perform the most basic daily activities. He can't speak a
word, although he can hear (sometimes he can move the eyes to look for the
origin of a new voice speaking) and he seems to understand at least a part
of what he's been told by his family. However, in the last weeks he has
started to speak during his sleep time (and only during his sleep time). In
his talking he seems to be speaking with family or acquaintances. His family
thinks he is speaking about recent-past daytime events, but I think it could
be remembering events before the stroke happened. I have absolutely no
professional knowledge about his medical situation, neither I am related
with his medical care, but, out of curiosity I have been asked about this
circumstance. I had to admit I had no idea of what can be the reason for
this sleep-time only talking, and less I know about what can it mean about
his recovery. However, I am really curious about this. Could some list
member more familiar with such cases recommend some bibliography (specially
from the linguistic and cognitive point of view) about this phenomenon?

Many thanks in advance,

Daniel Riaño, CSIC, Madrid