even if there is the slightest glimmer of short-term memory,
  some momentary awareness, there *is* consciousness, even if
  minimal.

  I've worked with extremely disabled kids - full time for a year
  - in my early 20s.

  Language, ability to perform tasks that indicate to the outside
  world that "there is somebody in there", is not required, imo,
  to determine consciousness.

  Even brain scans are imperfect, for the very procedure for
  measuring mental activity can be distressing and cause someone
  receiving an input-overload from the environment, could shut
  down out of fear and show nothing much on the instruments.