Understanding emotions in the brain could lead to the discovery of new molecules
September 12, 2018
By André Julião | Agência FAPESP – Lauri Nummenmaa presents several studies in succession, concluding each one with a joke. The audience invariably laughs, making the speaker smile with satisfaction.
If he were subjected after the presentation to a positron emission tomography (PET) scan, the images would probably show activation of the endogenous opioid receptors in the brain of this professor from Turku University in Finland.
The link between the ability to make people laugh and the construction of social bonds is a focus of Nummenmaa’s research. He spoke about his studies of emotions, with and without the use of PET scans, during the São Paulo School of Advanced Science on Social and Affective Neuroscience held on August 20-31, 2018, at Mackenzie Presbyterian University in São Paulo, Brazil, with FAPESP’s support.
PET scans are widely used to diagnose and treat a range of disorders, including cancer and heart disease, among others, but they are not as common in brain research. “However, they’re much more powerful than people think as a tool in our field of research,” Nummenmaa said.
Resistance to PET scans is frequent partly because it requires the injection of radioactive material into the patient. The functioning of various types of tissue is displayed as radioactive isotope decay is detected in the bloodstream. “The amount of radiation is very small and entirely safe,” Nummenmaa said.
Currently, he is using the technique to study the behavior of cerebral opioid receptors, which regulate motivational processes and pleasure. Their action in the brains of obese people was the subject of a study described during Nummenmaa’s presentation.
An article on the study published this year in Nature Communications shows that brain regions linked to the reward system are activated simply by looking at appetizing photographs of food.
“Variations in the brain’s opioid receptors may explain why some people experience cravings when stimulated by suggestion, heightening the risk of weight gain and obesity,” he said.
Interest in explanations for certain kinds of human behavior may help explain why Nummenmaa’s studies are featured by specialized publications from time to time.
In one study, inspired by research showing that nonhuman primates use social touch to maintain and reinforce social structures, 1,368 individuals from five European countries (Finland, France, Italy, Russia, and the UK) took a test designed to examine the role of social touching in human relationships.
The volunteers were shown silhouettes of human bodies and asked to color the body areas members of their social networks (family, friends and acquaintances) would be allowed to touch.
For participants in all five countries, the areas that could be touched correlated directly with the emotional bonds they had with the toucher, regardless of when they last met.
“Close acquaintances and family members were touched for more reasons than less familiar individuals,” Nummenmaa said. He then made the audience laugh by displaying a chart showing that people in the UK were least likely to allow others in their social networks to touch them.
In 2014, another study published by his group in PNAS drew attention by revealing other maps of the human body, in this case pinpointing the parts involved in different emotions.
The images ranged from an almost inactive body, representing depression, to bodies with activity in the head, chest and stomach, representing love.
Use in healthcare
According to Nummenmaa, PET scans provide such detailed images of the brain that they can help unearth the origin of psychiatric disorders and even contribute to the development of new therapies.
“Techniques such as PET are excellent in that we can genuinely come close to locating the molecular and biological underpinnings of various feelings in the brain,” he told Agência FAPESP.
“In the broad view, this means they can be used to help identify and develop new drugs. When we try to understand the affective brain at that level, the information helps the people who actually develop novel molecules and drugs to understand how these conditions originate.”
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