Until now, most of the research on the influence of intestinal organisms on emotions has been carried out on animals. It has been proven, for example, that the intestinal flora of rodents can modify their behavior.
Interactions between the brain, the intestine and the microbiota can play an important role in human health and behavior. Although rodent models have demonstrated the effects of intestinal microbiota on emotional, nociceptive and social behaviors, to date there is little human translational evidence.
In this study, we identified the cerebral and behavioral characteristics of healthy women grouped by intestinal microbiota profiles Faecal samples from 40 healthy women, aged between 18 and 55 years, were analyzed and the results of the analyzes were divided into two groups, depending on the composition of their intestinal flora.
One of the groups analyzed showed a greater abundance of one type of bacteria called Bacteroides, while the other group had a greater abundance of another bacteria called Prevotella. Next, the researchers scanned participants brains through magnetic resonance imaging, while showing them various images designed to provoke an emotional reaction, whether positive, negative or neutral.
In this way, they were able to discover that people who had an intestinal flora dominated by Bacteroides had a denser gray matter in the frontal cortex and the insular regions, the areas of the brain specialized in the treatment of complex information. They also showed a more bulk hippocampus, the brain area involved in memory.
However, the people in the second group had less developed those same brain areas, confirming that there is a close relationship between the emotional, sensory and attention regions that we have in the brain, and the composition of the intestinal flora.
Also, participants who had more Pretovella bacteria showed poorer activity in the hippocampus region, while suffering higher levels of anxiety, stress and irritability when looking at the images. According to the researchers, a hippocampus less involved in negative images may be associated with a disproportionate emotional reaction.
Although the people participating in this study were healthy, these results indicate that the profiles obtained from the structure of the intestinal flora constitute a factor of vulnerability for these people, in the face of possible psychiatric disorders.
The researchers point out that these results should not be considered conclusive, since the sample analyzed is small. Therefore, they propose to carry out this study with many more people in order to better understand the relationship between the intestinal flora, emotions and human behavior.