Rolling debate … experts are undecided about what brain scans can reveal.
BEFORE the US presidential election in 2008 scientists reported they had, quite literally, peered into the minds of swinging voters.
When a group of people were shown the words ”Democrat” or ”Republican” while undergoing a brain scan they showed high levels of activity in a region called the amygdala.
The scientists concluded that because this region was associated with anxiety, the participants felt that way about the political parties.
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The conclusion was strongly resisted by a group of rival neuroscientists who published a response to the study several days after it was reported in The New York Times.
It was not possible to determine whether a person was anxious simply by looking at the activity in a particular brain region, they said. ”This is because brain regions are typically engaged by many mental states, and thus one-to-one mapping between a brain region and a mental state is not possible.”
This stand-off typifies the rolling debate over what brain scans can really show.
To date, many studies claim to have found the regions of the brain for things as diverse as love, sarcasm, sex drive and even voting choice, fuelling the idea that the brain is made up of modules and individual parts.
Brain scans are generally taken with functional magnetic resonance imaging, or fMRI, which has, for the first time, allowed scientists to watch the flow of activity in the brain in real time without cutting open the skull.
But despite the clarity that comes with fMRI, it does not take photographs.
An American psychologist, Diane Beck, said the highlighted region of the brain in an fMRI did not show not a direct measure of that region’s activity.
”The construction of the colourful images we see in journals and magazines are considerably more complicated, and considerably more processed, than the photo-like quality of the images might lead one to believe,” said Dr Beck, of the University of Illinois.
So has fMRI really bridged human understanding of how the thoughts, emotions and feelings of our mind are linked to the soggy, 1.5-kilogram mass of tissue inside the skull?
The debate around fMRI’s powers for probing the mind came to a head in 2009 when an American review found almost half of fMRI studies of emotion and personality had overstated their data linking a specific brain region to an emotion or personality trait.
In a recent article published in the journal Perspectives on Psychological Science, an American psychologist Gregory Miller agreed. ”The rush in recent decades to construe a host of psychological events as being biological events is, at best, premature,” he wrote.
Ulrich Schall, a psychiatrist and psychologist at the University of Newcastle, said fMRI did not directly measure brain activity; instead it measured blood flow in the brain, which increased as neurons became active, and was therefore an indirect measure of their activity.
When someone was performing a specific mental task it was not possible to clearly identify the biological basis of that task in the brain, Associate Professor Schall said. That was just the interpretation of a scientist.
And unless studies were well designed, he said, the interpretation might be meaningless.
But fMRI clearly had a role in studying the brain. It was good for measuring brain development and studying people with mental disorders, he said.
Associate Professor Schall said scientists were confident of the function of primary processing regions of the brain, such as the areas associated with speech, vision and movement.
But scientists were still far away from understanding the basis of more complex cognitive functions such as numeracy, social interactions, intentions of people and planning, he said. ”These things are certainly not localised and need the combination of many parts of the brain.”
Like many scientists, he believed everything that people experienced in their minds, such as thoughts and feelings, had a physical or biological origin.
”But I use the word believe because I don’t have final proof of that,” he said.
Sourced & publ;ishd by Henry Sapiecha
