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On 8th September 2006, the journal Science published a paper showing how MRI had revealed how a patient in a vegetative state seemed capable of understanding and responding to certain commands. Mass media attention ensued, triggering an important debate regarding how medicine should or should not treat such patients given that this particular patient was apparently conscious yet outwardly unconscious and unresponsive. Adrian Owen and his colleagues at the Medical Research Council Cognition and Brain Sciences Unit and the Wolfson Brain Imaging Centre, Addenbrooke's Hospital, in Cambridge, UK, together with researchers at the Cyclotron Research Centre and Neurology Department, at the University of Liège, Belgium, used functional magnetic resonance imaging (fMRI) to measure the neural responses of the 23-year old patient. The patient had existed in a persistent vegetative state (PVS) for five months since emerging from a coma following a car accident in July 2005. The team recorded the brain response of twelve healthy volunteers asked to imagine themselves playing tennis and then to picture themselves walking around their homes. Specific regions of the brain involved in controlling movement were activated. The team then asked the patient the same questions and obtained almost identical fMRI patterns to those seen in the healthy volunteers. Similar results had been obtained in initial tests with responses to simple words. This, the researchers say, represents the first evidence of awareness in a patient in a persistent vegetative state. Patients have been shown to respond transiently to the spoken word, but Owen says that the observed activity lasted for the duration of the test until they asked the patient to stop "playing tennis". Owen himself cautions that this finding, while significant, should not be generalised to all patients in a PVS. There are different degrees of PVS, which result from very disparate injuries. Indeed, he suggests that the findings may not be applicable to the majority of patients in a PVS. "This is unlikely the case for all vegetative patients," he says, "It's such a heterogeneous group; they all have brain injuries of different types. The conventional definition of PVS states that patients cannot experience pain and suffering as these are attributes of consciousness. Owen's work could represent a challenge to that tenet especially if these preliminary investigations prove reproducible in other PVS patients. "We need to try this technique in other patients," Owen told SpectroscopyNOW, "in particular those for whom existing clinical investigations have left some ambiguity about the diagnosis." The next step will be to establish whether or not fMRI could be developed to allow some form of communication with such patients, he added. Lionel Naccache of the Clinical Neurophysiology Department, at Hôpital de la Pitié-Salpêtrière, in Paris, France, however, questions whether the patient is conscious in the strictest sense. "If this patient is actually conscious, why wouldn't she be able to engage in intentional motor acts," he asks, "given that she had not suffered functional or structural lesion of the motor pathways?" Fundamentally, the test of consciousness is the patient's own exclamations. "The ability to report one's own mental state is the fundamental property of consciousness," says Naccache. Clearly the patient investigated by Owen could not do this. Their indirect probing of brain function may ultimately have interpretations other than the PVS patient having consciousness. Naccache adds that the work nevertheless, "paves the way for future functional brain-imaging studies on comatose and vegetative state patients." He suggests that careful experimental design and fMRI studies of other patients may take us closer to a more direct indicator of consciousness without our having to rely on the patient declaring, "I think, therefore I am!" Related links:
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fMRI reveals similar activity in volunteers and PVC patient |
