|Searching the brain for happiness
Por Dr Morten L Kringelbach
For thousands of years people have pursued happiness, but the problem has been that it has always been seen as a kind of fuzzy concept.
In November 2005 the Dalai Lama was invited to speak at the annual meeting of the Society for Neuroscience in Washington DC.
While this event was not without controversy, his speech was generally well received and surprised many scientists with his remarkable open-mindedness, particularly concerning the validity of neuroscientific enquiry.
The Dalai Lama described a normal person's mind as "a troublemaker" and confessed that he "still feels anger and fear".
Meditation, he said, can help. But he was not adverse to other paths and volunteered himself as a patient if neuroscientists wanted to pursue easier ways to quell the "troublemakers of the mind".
The pursuit of happiness is a preoccupation for many of us and has probably been since the dawn of mankind.
Yet few of us come close to achieving this state with any regularity.
And even when happiness finally descends upon us, we often only realise it after the fact.
The neuroscience of happiness and well-being is still in its infancy.
So far, the focus of research has been on two related but perhaps somewhat distant cousins: pleasure and desire.
Reward would seem to be central to both of these states and so has been studied in other animals by behavioural psychologists since at least the beginning of the 20th century.
In studies during the 1950s psychologists James Olds and Peter Milner working at McGill University in Canada, found that rats would repeatedly press levers to receive tiny jolts of current injected through electrodes implanted deep within their brains.
When this brain stimulation was targeted at certain areas of the brain the rats would repeatedly press the lever - even up to 2000 times per hour.
In fact they would stop almost all other normal behaviours, including feeding, drinking and sex.
These findings seemed to suggest that Olds and Milner had discovered the pleasure centre in the brain, and it turns out that these overlap with the regions damaged in Parkinson's disease.
The main chemical aiding neural signalling in these regions is dopamine, and so it was quickly dubbed the brain's "pleasure chemical".
Additional human studies during the 1960s by Robert Heath at Tulane University in the US tried to take advantage of these findings in some ethically questionable experiments on mentally ill patients.
Infamously, they even implanted electrodes to try to cure homosexuality. This line of research was eventually stopped.
Although the researchers also found compulsive lever pressing in some patients, it is not clear from these patients' subjective reports that the electrodes did indeed cause real pleasure.
Wanting and liking
Instead, recent work by Kent Berridge, at the University of Michigan in the US, indicates that the electrodes may have been activating the anatomical regions that are involved in desire rather than pleasure.
Investigating reward systems in rats, Berridge found that they have specific facial expressions for pleasant and nasty tasting foods.
Sugary food makes them lick their lips contentedly - just as human infants do, whereas a bitter taste leads to a disgusted, lip-curling expression.
When Berridge manipulated the rats' dopamine levels, he found that their expressions remained unchanged.
Berridge is therefore proposing a distinction between desire and pleasure - wanting and liking - in terms of both the brain regions and the neurochemical substances that mediate these subjective states.
The dopamine system appears to encode desire while the opioid system, which contains our own natural morphine-like compounds, is closer to pleasure.
It is clear, however, that rats are different from humans.
Pleasure and desire are complex emotions in humans, and so there are still many interesting things to learn.
Central to current research is a brain region called the orbitofrontal cortex, a brain region that is evolutionary more recently developed in humans and has connections to both the opioid and dopamine systems.
Using neuroimaging, we have found that it contains regions that correlate with subjective reports of pleasure.
What can this research ultimately tell us about happiness, pleasure and desire?
Could happiness be best described as pleasure without desire, a state of contentment and indifference?
Such a state is perhaps akin to the kind of bliss that buddhists actively seek through meditation.
If so, it is possible that neuroscientists may one day find ways to help induce this state.
We might then have choice of a true utilitarian society where the overall happiness can really be maximized just as the 18th century philosopher Jeremy Bentham wanted.
Although the question of whether such a society would be desirable and pleasurable still remains to be answered.
The Dalai Lama was clearly interested in the end state of happiness, rather than the means by which it is achieved.
However, he also spoke of how humans have "much conflicting emotion, much bad emotion, jealousy, anger, fear. This is our great troublemaker."
He reminded the audience of the "fundamental values of compassion and affection" that are "important to the development of body and brain".
It would seem prudent for future research on happiness, pleasure and desire not to ignore this compassionate plea for human dignity, while tinkering with the very core of what makes us human.
|| 02/05/2006. BBC News.