Motus Mentis

An item in the news yesterday raises once again the stubborn puzzle of consciousness. A 23-year-old British woman who has been in a “vegetative state” for five months has been shown by a sophisticated scanning technique to exhibit, in response to verbal stimuli, patterns of brain activity that are indistinguishable from those occuring in normal, conscious volunteers.

The test, known as a functional MRI (fMRI), relies on the fact that the hemoglobin in blood, which contains iron, has varying magnetic resonance properties that depend on its state of oxygenation. This allows for an MRI to detect the dynamic oxygenation of the parts of the brain, which serves to indicate which regions are active. In the case in question the young woman, who appears from without to be utterly unconscious, seems inwardly to be interpreting spoken suggestions just as she would were she up and about. She responded to a suggestion that she imagine herself playing tennis by lighting up the appropriate motor-control areas.

So the question is: Is she conscious? The experts disagree.

The question has profound ethical and philosophical ramifications. Are her brain activities “mental”? Are they “intentional” (in the philosophical sense of the word)? They seem indistiguishable from what would be going on were she conscious, and they occur in reaction to the same stimuli that we would normally expect to cause mental events. My own view of intentionality is that it is not dependent on consciousness; that there are going to turn out to be specific neurological conditions for consciousness that are not being met in this poor subject’s brain. So the possibilites are:

A) That she is quite unconscious. Her brain’s intentionality engine is running nonetheless, but she has no subjective experience whatsoever.

B) That she is in a sort of dream – not fully conscious, and not aware of her predicament, but in an arguably subjective state nonetheless. It is known that the brain, when we are asleep and dreaming, enters a state called REM atonia, in which the neurotransmitters that enable muscular activity are shut off. (This handy feature has evolved, presumably, to keep us from running off cliffs, etc., as we dream, and when it fails we have a problem.)

C) That she is entirely conscious, and completely “locked in“. This is perhaps the most frightening thing one can imagine, and I do hope it is not the case here.

I had thought that routine brain-activity testing was already sensitive enough that a condition such as this woman’s would not be mistaken for a “vegetative state”, but it seems that is not the case; the fMRI apparatus is not something most hospitals have access to.

The woman’s head trauma is apparently quite slight – nothing at all like the massive, global damage caused by oxygen deprivation, as in the case of Terri Schiavo – and it would be very interesting to know exactly what the extent of her injuries is. I have heard it suggested that the reticular formation seems to play an important role in consciousness; I wonder if hers is injured. Likewise, the corpus striatum, the substantia nigra and the subthalamic nucleus play key parts in motor activity; if she is conscious but “locked in”, perhaps she has damage to these areas. If any of this detailed information about her case is mentioned anywhere, I haven’t seen it.