Scanning a brain that believes it is dead

What is going on in the brain of someone who has the deluded belief that they are brain dead? A team of researchers led by neuropsychologist Vanessa Charland-Varville at CHU Sart-Tilman Hospital and the University of Liege has attempted to find out by scanning the brain of a depressed patient who held this very belief.

The researchers used a Positron Emission Tomography (PET) scanner, which is the first time this scanning technology has been used on a patient with this kind of delusion – known as Cotard's syndrome after the French neurologist Jules Cotard. The 48-year-old patient had developed Cotard's after attempting to take his own life by electrocution. Eight months later he arrived at his general practitioner complaining that his brain was dead, and that he therefore no longer needed to eat or sleep. He acknowledged that he still had a mind, but (in the words of the researchers) he said he was "condemned to a kind of half-life, with a dead brain in a living body."

The researchers used the PET scanner to monitor levels of metabolic activity across the patient's brain as he rested. Compared with 39 healthy, age-matched controls, he showed substantially reduced activity across a swathe of frontal and temporal brain regions incorporating many key parts of what's known as the "default mode network". This is a hub of brain regions that shows increased activity when people's brains are at rest, disengaged from the outside world. It's been proposed that activity in this network is crucial for our sense of self.

"Our data suggest that the profound disturbance of thought and experience, revealed by Cotard's delusion, reflects a profound disturbance in the brain regions responsible for 'core consciousness' and our abiding sense of self," the researchers concluded.

Unfortunately the study has a number of serious limitations beyond the fact that it is of course a single case study. As well as having a diagnosis of Cotard's Delusion, the patient was also depressed and on an intense drug regimen, including sedative, antidepressant and antipsychotic medication. It's unclear therefore whether his distinctive brain activity was due to Cotard's, depression or his drugs, although the researchers counter that such an extreme reduction in brain metabolism is not normally seen in patients with depression or on those drugs.

Another issue is with the lack of detail on the scanning procedure. Perhaps this is due to the short article format (a "Letter to the Editor"), but it's not clear for how long the patient and controls were scanned, nor what they were instructed to do in the scanner. For example, did they have their eyes open or closed? What did they think about?

But perhaps most problematic is the issue of how to interpret the findings. Does the patient have Cotard's Delusion because of his abnormal brain activity, or does he have that unusual pattern of brain activity because of his deluded beliefs? Relevant here, but not mentioned by the researchers, are studies showing that trained meditators also show reduced activity in the default mode network. This provides a graphic illustration of the limits to a purely biological approach to mental disorder. It seems diminished activity in the default mode network can be associated both with feelings of being brain dead or feelings of tranquil oneness with the world, it depends on who is doing the feeling. Understanding how this can be will likely require researchers to think outside of the brain.

Further reading

Charland-Verville, V., Bruno, M., Bahri, M., Demertzi, A., Desseilles, M., Chatelle, C., Vanhaudenhuyse, A., Hustinx, R., Bernard, C., Tshibanda, L., Laureys, S., and Zeman, A. (2013). Brain dead yet mind alive: A positron emission tomography case study of brain metabolism in Cotard's syndrome. Cortex DOI: 10.1016/j.cortex.2013.03.003