The magazine, Science (Vol.366, p. 587), carried an article “Microbiota and the social brain”. Below are some excerpts.
Increasingly, it is recognized that the microbes resident in the gastrointestinal tract can influence brain physiology and behavior. [These biota] can signal to the brain via a diverse set of pathways, collectively known as the microbiota-gut-brain axis. In the absence of a microbiota, germ-free mice exhibit alterations to several central physiological processes such as neurotransmitter turnover, neuroinflammation…[etc.] Perhaps as a result of these neural alterations, the behavior of rodents lacking these microbiota–especially social behavior–[emphasis mine] is remarkably different from that of rodents colonized with bacteria. Conversely, supplementation of [germ-free] animals with certain live bacteria (e.g. Bifobacterium and Lactobacillus) can lead to notable improvements in social behavior both in early life and adulthood.
I believe it is safe to assume that most of us (if not all our leaders) like to believe that they are guided more often by reason rather than by ‘gut feeling’, but it may be a mistake to believe that some ‘more visceral’ factors are not operative as well. For example, we might say “that was a heart-felt response.”–even when we realize that it was the heart’s response to our endocrine glands that was operative. It took humankind quite some time to realize that our brains were NOT primarily useful for reasoning but rather for cooling the blood. When it comes to dealing with the Covid-19 pandemic, we should be very suspicious of advice based on the ‘gut-feeling’ that internal UV radiation or consuming ‘Lysol Gummies’ might be worth trying. Perhaps the White House physician could recommend that his patient substitute large helpings of yoghurt or kefir for the hydroxychloroquine he prefers.