This whole story is really very fascinating, although a few details seem a bit odd.
For example, the patient didn't answer the last question because.. he fell asleep? I would imagine if I was trapped inside my body and suddenly given a mechanism to communicate, I would be too excited to fall asleep.
Did they observe any signs of excitement that I would expect a person to feel in this situation? Increased heart rate or other brain activity? Did the man try to convey his own message using the new-found communication mechanism?
It almost sounds like they are communicating with some small ghost of the man's subconscious, something that can respond to basic queries and recall memories, but lacks what we would really consider a consciousness.
Actually, detecting brain activity in an MRI requires long aquisition times. Around 30 seconds per answer at least (which is the duration used in this study AFAIK). That means that a single "yes" (imagining you're playing tennis) or "no" (imagining you're walking in your house) requires 30 seconds of sustained attention.
This patient is obviously severely brain damaged.
If you've ever seen a person recovering from brain trauma, you'll know that their ability to focus is usually minimal. Answering questions for this patient may very well have been exhausting. This means that out of the other 22 patients in the study, some may be conscious but unable to cooperate long enough for the mnesic trace to be recorded.
Regarding other signs of activity, you can't detect random activity using fMRI. I haven't read this paper so I don't know the details (I'm only familiar with previous studies done by this team), but regarding heart rate, blod presure, etc, the brain damage may prevent it from occurring too.
Since he was only able to produce yes and no ansers using a contrieved process, he was of course unable to produce any other message.
The idea that the patient was exhausted came to my mind as well.
Imagine being locked-in for so many years, and then suddenly being asked to imagine things. It's not as easy as it sounds: Imagining something in such a strict order over such a long period of time is actually quite exhausting.
For example, the patient didn't answer the last question because.. he fell asleep? I would imagine if I was trapped inside my body and suddenly given a mechanism to communicate, I would be too excited to fall asleep.
They probably made that assumption because people fall asleep inside MRI's all of the time, especially during extremely long fMRI tests, when they try to isolate the senses (i.e. it's very dark, you wear earplugs and ear phones). Also, the brain damage might predispose someone to have a short attention span/wakeful periods.
Did the man try to convey his own message using the new-found communication mechanism?
If I understand correctly, he was given the means to convey "yes" by imagining himself playing tennis. The concept of "no" was encoded by the absence of "yes".
If he had wanted to send some message, like "tell my children I love them", or "I feel pain in my abdomen", how would he encode it?
He certainly can't send messages as complicated as that, but if I only had one bit to flip, I would be flipping it as much as possible to get someone's attention.
That said, he probably did the correct thing by simply answering their questions. That shows that "someone is home" better than flipping his bit randomly.
For example, the patient didn't answer the last question because.. he fell asleep? I would imagine if I was trapped inside my body and suddenly given a mechanism to communicate, I would be too excited to fall asleep.
Did they observe any signs of excitement that I would expect a person to feel in this situation? Increased heart rate or other brain activity? Did the man try to convey his own message using the new-found communication mechanism?
It almost sounds like they are communicating with some small ghost of the man's subconscious, something that can respond to basic queries and recall memories, but lacks what we would really consider a consciousness.