A new brain study has pointed out why most mammals experience moments of overwhelming desire – be it for food, sex or other things – that can be followed by seemingly magical feelings of satisfaction. But the find suggests we are often likely to be left wanting rather than satisfied.
According to a study recently published in the Journal of Neuroscience, wanting and liking are separate urges in the brain that are controlled by different circuits.
When these urges occur in sync, the impact on the brain is very powerful.
But there’s a catch. Mammal brains appear to have fewer mechanisms for pleasure than they do for desire.
“Our results suggest we all are inherently susceptible to wanting more than we’ll actually enjoy, at least in certain situations,”co-author Kent Berridge told Discovery News.
Berridge, a University of Michigan psychology researcher, added, “If separable brain circuits exist for liking and wanting, then a person who had selective activation of the wanting circuit would want more without liking more.”
Such want/like dissociations can lead to addictions with drugs, sex, food, gambling and more, the researchers believe. Some people also appear to be prone to experiencing the out-of-sync phases.
For the study, Berridge and colleague Kyle Smith used a painless microinjection technique to deliver droplets of an opioid drug into a pleasure hotspot within the brains of rats.
The drug caused the rats to want to eat three times their normal amount of food – in this case, sugar – while liking it twice as much as usual.
The scientists measured the “like” degree in rats by studying their facial expressions and behaviours while they ate. These included lip and paw licking.
The researchers then turned off a rat pleasure circuit by microinjecting an opioid suppressant into another part of the rodent’s brain. The rats reacted by still wanting sugar, but exhibited no extra signs of liking it.
Finally, the scientists used a technique called Fos mapping, which shows activated portions of the brain based on colour changes due to proteins that affect certain neural circuits.
This, and the other experiments, revealed the separate want and like “hedonic hotspots”in two areas deep within the brain. Rats, humans and other mammals share these same regions and related circuitry, so rat desire can be comparable to human desire.
Source:The Times Of India
