Using MRI to diagnose Vegetative States

Today, the front page of the NYTimes website hosts an article describing a study published in the New England Journal of Medicine, wherein doctors took MRI scans of patients in a vegetative state, and asked yes or no questions. Depending on which areas of the patients brain lit up, the doctors declared that the patients were, or were not, correctly diagnosed as vegetative. This research comes from a group that in 2006 published a paper wherein they asked a non-responsive patient to imagine walking through her house, and recorded areas of her motor cortex lighting up. In the current study, the researchers asked vegetative patients hooked up to the MRI machine to complete two imagery tasks:

  1. "imagine standing still on a tennis court and to swing an arm to "hit the ball" back and forth to an imagined instructor."
  2. "imagine navigating the streets of a familiar city or to imagine walking from room to room in their home and to visualize all that they would "see" if they were there."

The paper reports that from the pool of 54 patients, 5 were identified that could modulate their brain activity in response to the imagery tasks (with their brain activity compared to that of healthy subjects).

In addition, patients were asked to complete a communication task. An excerpt from the paper's methods explains the generation of control data from healthy participants:

Before each of these imaging sessions, participants were asked a yes-or-no question (e.g., "Do you have any brothers?") and instructed to respond during the imaging session by using one type of mental imagery (either motor imagery or spatial imagery) for "yes" and the other for "no." The nature of the questions ensured that the investigators would not know the correct answers before judging the functional MRI data. Participants were asked to respond by thinking of whichever imagery corresponded to the answer that they wanted to convey.

Then, in the case of one patient in a vetetative state:

In this patient, the activity observed on the communication scan in response to five of the six questions closely matched that observed on one of the localizer scans (Figure 2A and 2C and Figure 3A and 3C). For example, in response to the question "Is your father's name Alexander?" the patient responded "yes" (correctly) with activity that matched that observed on the motor-imagery localizer scan (Figure 3A). In response to the question "Is your father's name Thomas?" the patient responded "no" (also correctly) with activity that matched that observed in the spatial-imagery localizer scan (Figure 3C).

The paper presents their methods as a novel use of functional MRI, and appears to have a high success rate for identifying brain activity in patients previously diagnosed as vegetative. The authors seem keen upon their use of MRI as an important diagnostic tool to "bridge the dissociation that can occur between behavior that is readily observable during a standardized clinical assessment and the actual level of residual cognitive function after serious brain injury."

However, the brain, and consciousness are undoubtedly more complex than "yes" or "no" questions. With no good handle on how consciousness is generated in the brain, is it too early to say that we can image a brain and determine state of mind?  Is the (relatively simplistic) model of equating brain activity to conscious identity one that will be lodged into the public mind? With the high-profile nature of the article help enhance public awareness of the importance of neuroscience research and the complexities of the brain and its activity, or will it focus public attention even more on the blind use of fMRI to solve problems ranging from whether a person is lying to whether a person is still a person at all?

Trace of Thought is Found in "Vegetative" Patient. Benedict Carey for the NYTimes.

Monti et al. Willful Modulation of Brain Activity in Disorders of Consciousness. 10.1056/NEJMoa0905370


Astra Bryant

Astra Bryant is a graduate of the Stanford Neuroscience PhD program in the labs of Drs. Eric Knudsen and John Huguenard. She used in vitro slice electrophysiology to study the cellular and synaptic mechanisms linking cholinergic signaling and gamma oscillations – two processes critical for the control of gaze and attention, which are disrupted in many psychiatric disorders. She is a senior editor and the webmaster of the NeuWrite West Neuroblog