These little guys may be doing the thinking for you. Science Daily reports:
For the first time, researchers have conclusive evidence that bacteria residing in the gut influence brain chemistry and behavior.
The findings are important because several common types of gastrointestinal disease, including irritable bowel syndrome, are frequently associated with anxiety or depression. In addition there has been speculation that some psychiatric disorders, such as late onset autism, may be associated with an abnormal bacterial content in the gut.
For each person, the gut is home to about 1,000 trillion vital bacteria with which we live in harmony. Any disruption can result in life-threatening conditions, such as antibiotic-induced colitis.
Working with healthy adult mice, the researchers showed that disrupting the normal bacterial content of the gut with antibiotics produced changes in behavior; the mice became less cautious or anxious. This change was accompanied by an increase in brain-derived neurotrophic factor (BDNF), which has been linked to depression and anxiety.
When oral antibiotics were discontinued, bacteria in the gut returned to normal. “This was accompanied by restoration of normal behaviour and brain chemistry.”
To confirm that bacteria can influence behavior, the researchers colonized germ-free mice with bacteria taken from mice with a different behavioral pattern. They found that when germ-free mice with a genetic background associated with passive behaviour were colonized with bacteria from mice with higher exploratory behavior, they became more active and daring. Similarly, normally active mice became more passive after receiving bacteria from mice whose genetic background is associated with passive behavior.