Neuroscientists have figured out how the brain reacts to meeting and breaking up with a partner
The neurotransmitter dopamine, part of the brain's reward system, plays an important role in many processes related to motivation, memory, attention and other cognitive functions. It is also involved in regulating social bonding, which scientists know from past studies and experiments, including those involving laboratory mice and rats.
Although these rodents can form bonds, they do not form selective attachments to kin. That is why neurobiologists from the University of Colorado at Boulder (USA) decided to conduct a new series of experiments. This time the object of research to study the dynamics of dopamine release during social interaction was steppe, or prairie, voles (Microtus ochrogaster). Their peculiarity, which is inherent in only three to five percent of mammals, including humans, is considered to be the ability to monogamy.
Like humans, steppe voles tend to pair up for a long time, live together and raise offspring. It is also known that these animals experience something similar to grief when they lose a partner.
In the work, the results of which were published in the journal Current Biology, the researchers used a method of neuroimaging. To do this in the adjacent nucleus of the brain (nucleus accumbens) animals implanted a miniature fiber-optic sensor with a diameter of 0.2 millimeters and a length of five millimeters. This area is responsible for the motivation to seek different rewards - from water and food to drugs.
In this way, the scientists were able to track in real time what was happening in the brain when the voles were trying to get to a partner. In one scenario, the subjects pressed a lever to open a door and get into the chamber to him, while in another, they climbed over an obstacle.
Whenever the sensor picked up a surge of dopamine, it began to glow. When the voles pulled a lever or climbed over the obstacle to see their "soulmate," the fiberglass "flashed like crazy" and continued to glow as the pair sniffed and snuggled together, said Anne Pierce, one of the study's authors.
In contrast, when a random vole was on the other side of the door or barrier, dopamine levels decreased and the sensor glow faded. According to the scientists, the experiment not only confirmed the role of dopamine for motivation to find a mate, but also clearly showed that when you are with your mate through the reward center of the brain passes more dopamine than near a stranger.
In another series of experiments, a pair of voles were separated for four weeks - an eternity by the standards of these rodents, whose lives rarely last more than one or two years. When, after separation, the animals met again, they recognized each other, but the former, characteristic for couples, a surge of dopamine almost disappeared. Simply put, the voles' brains now reacted to the former partner in the same way as to any other congener.
The researchers believe that this is a kind of defense mechanism in the brain in case of the loss of a loved one. It allows them to continue living and form a new couple in case of separation, rather than endlessly tormented by unrequited love.
The authors hope that their findings will be useful to people who have experienced a painful breakup or death of the other half. However, before this happens, it remains to be seen how far the results of experiments with voles are applicable to humans.
Nevertheless, the researchers believe that understanding similar mechanisms in the brain will help in the search for new methods of treating mental disorders, such as Prolonged grief disorder.