Cogito ergo sum by MRI.

What is left of the human being when the brain is badly damaged has been a question for philosophers and theologians. Now, however, an imaginative series of experiments using functional magnetic resonance imaging (MRI) of the brain, culminating in the article by Monti and colleagues in this issue of the Journal,1 has revealed a form of preserved cognition in ostensibly unconscious patients. The unfortunate term “vegetative” has been used to describe patients whose eyes open after a period of coma but who lack any meaningful responses to stimuli. Open eyes give the impression of normal alertness, but the patient’s behavioral repertoire is limited to reflexive actions such as posturing or purposeless movements, roving eye movements, swallowing, and yawning. A task force has suggested that the term “persistent vegetative state” be used to describe patients who remain in a vegetative state for more than 3 months after an anoxic brain injury or 12 months after cranial trauma, since improvement after these periods is highly unlikely.2 The more recently introduced term “minimally conscious state” refers to limited, erratic, but meaningful verbal and motor responses to commands or environmental circumstances. The difference between these two states is fundamental only if one attributes different degrees of conscious experience to each. It is known that exposure to personally meaningful information such as a patient’s own name (but not other names) activates the cerebral cortex in some patients in a vegetative state.3 Although this activation is surprising, it does not necessarily reveal conscious experience. In the study reported by Monti et al., one of two parts of the cerebrum was induced to activate in 5 of 54 unresponsive or minimally responsive patients. This activation was cued by verbal instructions to think about navigating one’s home or a familiar city or to imagine playing tennis. Moreover, the regions activated were the same in unresponsive persons and in healthy control subjects. The authors have described this ability to detect awareness by means of functional MRI before,4 but here they report the frequency of the finding. Even in a preselected population, brain activation was infrequent, but it occurred often enough that it will now be difficult for physicians to tell families confidently that their unresponsive loved ones are not “in there somewhere.” The error rate in the clinical diagnosis of the vegetative state is high, and Monti et al. indicate that some patients who were initially classified as being in a vegetative state but who showed volitional cortical activation had behavioral responses when reexamined that put them into the category of minimal consciousness. This finding emphasizes that clinicians should make these pronouncements only after detailed and repeated examinations. Previous studies have also shown that cortical activation in response to meaningful stimuli and imagined activities indicates a likelihood of awakening. These data suggest that functional MRI might supplement conventional neurologic examination in the classification and prognosis of patients with coma. A potential logical flaw clouds this surreal circumstance of trace brain patterns of apperceptive experience without the ability to signal consciousness. In response to a previous article regarding the same findings, Nachev and Husain5 point out that “the presence of brain activation is not sufficient evidence for the associated behavior —