Location of the mind remains a mystery

Where does the mind reside? It's a question that's occupied the best brains for thousands of years. Now, a patient who is self-aware ? despite lacking three regions of the brain thought to be essential for self-awareness ? demonstrates that the mind remains as elusive as ever.

The finding suggests that mental functions might not be tied to fixed brain regions. Instead, the mind might be more like a virtual machine running on distributed computers, with brain resources allocated in a flexible manner, says David Rudrauf at the University of Iowa in Iowa City, who led the study of the patient.

Recent advances in functional neuroimaging ? a technique that measures brain activity in the hope of finding correlations between mental functions and specific regions of the brain ? have led to a wealth of studies that map particular functions onto regions.

Previous neuroimaging studies had suggested that three regions ? the insular cortex, anterior cingulated cortex and medial prefrontal cortex ? are critical for self-awareness. But for Rudrauf the question wasn't settled.

So when his team heard about patient R, who had lost brain tissue including the chunks of the three 'self-awareness' regions following a viral infection, they immediately thought he could help set the record straight.

Not a zombie

According to the models based on neuroimaging, says Rudrauf, "patients with no insula should be like zombies".

But patient R displays a strong concept of selfhood. Rudrauf's team confirmed this by checking whether he could recognise himself in photographs and by performing the tickle test ? based on the observation that you can't tickle yourself. They concluded that many aspects of R's self-awareness remained unaffected. "Having interacted with him it was clear from the get go that there was no way that [the theories based on neuroimaging] could be true," says Rudrauf.

However, R does have severe amnesia, which prevents him from learning new information, and he struggles with social interaction.

Self-awareness and other high-level cognitive functions probably do not relate to the brain in a simple way, says Rudrauf. "They involve layers of abstraction and mechanisms that cannot be explained by standard functional-neuroanatomy." He suggests that there are fundamental mechanisms yet to be discovered. "We would all like simple answers to complicated questions, and we tend to oversimplify our conceptions about the brain and the mind," he says.

Linda Clare, a psychologist at Bangor University, UK, is also not surprised by the finding. "Awareness has many manifestations," she says. "It's not just a matter of a few brain cells."

Journal reference: PLoS ONE, DOI:10.1371/journal.pone.0038413

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