Faecal bacteria viewed with an electron microscope
Science Photo Library / Alamy Stock Photo
Rats that received gut microbiome transplants from lively human toddlers appear to exhibit a greater willingness to explore their surroundings. This discovery suggests that the bacteria present in our guts during childhood may have a role in shaping our personalities.
According to Harriët Schellekens at University College Cork in Ireland, who was not part of the study, “It suggests our microbes are active participants in emotional development, not just passive passengers.”
Recent studies have established a connection between the communities of microbes residing in our guts and our overall health, emotions, and moods. For instance, individuals lacking specific types of gut bacteria seem to have a higher susceptibility to depression or anxiety.
While it remains unclear whether these bacteria are the direct cause of these changes or if the microbial community changes in response to behavior, there is evidence to suggest that altering the composition of the microbiome can impact one’s mood. Studies have shown that fecal transplants from individuals with depression to rats can induce depressive behavior in the rodents, and individuals with depression who undergo fecal transplants have shown improvement in their symptoms in initial trials.
To further explore the potential link between the gut microbiome and temperament, Anna Aatsinki and her team at the University of Turku in Finland conducted a study where fecal samples from toddlers were transplanted into young rats.
The researchers first assessed the personalities of 27 2.5-year-old toddlers using standard temperament evaluations and observed their behavior while playing with a bubble gun. Based on these assessments, they identified 10 toddlers as exuberant and 8 as inhibited and introverted. Samples were collected from four exuberant and four inhibited toddlers, and these fecal samples were transferred to young rats for the study.
The rats were then subjected to various behavioral tests, and the results showed that rats with microbiomes from toddlers displaying high exuberance traits exhibited more exploratory behavior compared to rats in the control group or those receiving fecal transplants from inhibited toddlers.
Analysis of the rats’ brain tissue revealed differences in gene activity, particularly in neurons responsible for producing dopamine, a neurotransmitter associated with reward and risk-taking behavior. Rats that received transplants from inhibited toddlers showed reduced activity in these dopamine-producing neurons.
Harriët Schellekens commended the study for highlighting how the gut microbiome in early life may contribute to shaping behavioral tendencies and creating a link between microbes, human temperament, and brain function. This suggests a gut-brain pathway that influences curiosity, reward, and motivation through the dopamine system.
However, Aatsinki cautions against overstating the influence of gut microbes on behavior, noting that while temperament traits in adults are largely influenced by genetics, environmental factors such as the microbiome could play a role in shaping certain behaviors.
The exact role of microbes in driving behavior differences in children remains a topic for further investigation. It is possible that children with exuberant traits interact differently with their environment and food choices, leading to the development of a distinct microbiome.
