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Skip to 0 minutes and 8 seconds Hello, and welcome to the video about the relationship between the microbiome and our brain. We have seen in the previous activity that there is an axis that virtually connects our gut and our brain, and that microbiome plays a role in its functioning.

Skip to 0 minutes and 27 seconds This led some scientists to wonder: does a microbiome imbalance reflect itself also on mental health? Many of these studies are still drawing their results from animal models, but they can still provide useful insights and indications. The animals used in these studies are often ‘germ-free’ animals, which means that are animals that have no germ living in or on them. Germ-free animals are used because contamination from unknown bacteria would make the results impossible to interpret – instead, if we know exactly which strains of bacteria are part of the gut or skin microbiota, we can draw casual relationships between the presence of a specific strain and a behavioural or biological consequence.

Skip to 1 minute and 26 seconds More than fifteen years ago, researchers found out that germ-free mice exhibited an exaggerated hypothalamic-pituitary axis response to restraint stress, but this effect could be reversed after colonization with a specific probiotic bacterium. It was then shown that having no bacteria was definitively worse that having a single good bacterial strain co-existing with us, but what about the “bad” bacterial strains? It could well be that the simple unnatural condition of living with no coexisting bacteria at all harms the development, for instance, of the immune system. If this is the explanation for the finding we just discussed, then adding a known pathogenic bacterium should improve the response to stress.

Skip to 2 minutes and 25 seconds Instead, associating the mouse with a known strain of Escherichia Coli resulted in an increased stress reaction, underlining the importance of a “good” microbiome. More recent studies even showed that transplanting the microbiota from high-anxiety mice to low-anxiety mice could induce anxiety in the receiving animal; while inverting the direction of the intervention could /reduce/ anxiety in the mouse that received the transplant. The first studies in this field suggested that, to obtain these effects, the ‘gut recolonization’ by the new microbiome should happen in the first period of life, but evidence is now showing that this phenomenon can be observed also in adult animals. Similar results have been obtained with more

Skip to 3 minutes and 30 seconds ecological studies: in the early 2010, a group of scientist demonstrated that adding specific probiotic strains of lactobacilli to the usual feed caused a reduction of behavioural and neurochemical responses to stressful stimuli. These changes were thought to be mediated by an effect on neurotransmitter receptors on the brain, and more specifically of GABA, in areas linked with the processing of fearsome stimuli such as the amygdala and in areas important for the formation of memories, such the hippocampus. How do these finding translate to humans? Is there any proof that microbiome alterations can be responsible for some psychological illnesses? Some studies investigated the relationship between microbiome and psychological functions.

Skip to 4 minutes and 25 seconds A few years ago, a team of scientists from the University of California at Los Angeles found four weeks of probiotic supplementation, via a fermented milk product, could modulate the activity at rest of a network of brain areas, involved both in the perception of the internal state of the body and in the processing of emotions. More recently, some scientists have put forward the idea that gut dysbiosis could also be linked to autistic spectrum disorders. While the idea is incredibly interesting, as it would help us understand the genesis of this family of disorders, it is also far to be conclusively proven.

Skip to 5 minutes and 16 seconds You will find some links to external resources that talk about this idea, and our educators are be available to discuss it with you, and to answer question you might have on this delicate topic.

Gut-brain axis and our mind

In this video, we explore in more detail the relationship between the microbiome and our mind.

Most studies on the topic actually involve animals, as we already saw in the last activity, but scientists are also conducting interventional and correlational studies in humans.

In this video we will start by discussing some of the studies that analyse the role of the gut microbiota in the response to stress, and we will then move on to exploring the trials that tested microbiota-modifying supplements in humans

Some of the links between microbiota and the brain have only been a topic of scientific discussion in the last ten years. As such, it is much easier to find popular science articles that discuss how a certain food can “fix” our gut and mood, rather than reviews or consensus papers written by scientists.

This is particularly true when discussing the role of gut dysbiosis in psychological and psychiatric illnesses. In the ‘see also’ section we are linking two articles published by the website of the American Association for the Advancement of Sciences (AAAS, also known as the publisher of Science) that discuss the relationship between the microbiome and autism. (Note: the first article is more technical, but both links refer to the same study).

As you will see, the research is still in the very early stages, and it is definitively too early to draw any conclusion.

Given the particular nature of this topic, we remind you to be respectful of your fellow learners when commenting, and to keep in mind that we’re discussing cutting-edge areas of biological research, where the certainties are still scarce.

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Food for Thought: The Relationship Between Food, Gut and Brain

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