The gastrointestinal (GI) tract in humans provides a home for many (1014) bacterial organisms. The colonization of the GI by bacteria, or microbiota, starts at birth and continues throughout early development and life. These microbiota affect many bodily functions, aiding metabolism, modulating inflammation, and defending against harmful micro-organisms. Each person has a unique profile of microbiota, which is influenced by genetics and the environment. Healthy people, however, generally have similar numbers and distributions of microbiota. Interestingly, disorders of the GI tract have a high comorbidity with mental illness.
It is not surprising then that research in this field has grown, with labs hoping to gain a better understanding of the ‘gut-brain-axis.’ If these labs can elucidate the effect of microbes in the GI tract on the central nervous system, they could shed light on why more than half of patients with irritable bowel syndrome meet the criteria for mood disorders, or how GI tract disorders and mental illnesses can be more effectively treated.
Many researchers are currently focusing on how variations in the composition of microbiota impact physiology and contribute to disease, such as obesity and inflammation. Increasingly, studies have been revealing that these microbiota communicate with the brain and influence its function and behavior, potentially by neural, endocrine, and immune pathways.
We all know androgens and estrogens as sex hormones, right? You know, those chemicals that regulate reproductive behavior and ensure the continuation of species. There is definitely behavioral evidence of the biological importance of these steroid hormones, but could there be a way to quantitatively measure exposure to them? There is research that says yes, or at least, possibly. More
Ever wonder why people still “talk with their hands” when they’re on the telephone? We often use hand gestures while speaking even at times when the listener cannot see them. Gestures are processed in the same areas of the brain as speech (think sign language): the left inferior frontal gyrus (Broca’s) and the posterior middle temporal gyrus (Wenicke’s area). Hand movements help us to communicate more efficiently and emphasize certain points of the message we are trying to convey to our conversational partners. They’re an indication of our thought process throughout the discussion. Evolutionary insight proposes that the language brain regions, which originally supported the pairing of body language and meaning, have been adapted in humans for spoken language; however, we still don’t know precisely the reason why people gesture, and more interestingly, why some people use gestures more often than others. More
What would happen if humans were like turtles – alone at birth with no mom to guide them back home? We probably would not survive very long before getting attacked and/or eaten by something bigger than us. For many animal species, instinct guides survival. But for humans and other mammal species, nurture as an infant is crucial to our development.
Weaver et al investigated the phenomenon of nurture in rats. They noted that some rat moms extensively licked and groomed their pups, while others ignored their pups. Pups that received attention during the first week of life grew up to be happy and calm, while those that were ignored grew up to be anxious, and were more prone to disease. Epigenetics studies the genomic changes that occur in response to the external environment. The differences in behavior are due to a change in a glucocortocoid receptor (GR) gene during development. At birth, the gene is highly methylated and inactive. If a rat mother is attentive towards her pups, the pups’ GR gene gradually demethylates, making the gene more active. These pups will be more relaxed in response to stress. Those that were not given attention, and do not express the GR gene, respond poorly to stress. You can try being a rat mom in an interactive game here .
A related study by McGowan et al studied hippocampal tissue in humans that had committed suicide and been abused as a child, and humans that had committed suicide with no history of child abuse. When compared to controls and subjects that were not abused, the subjects that had been abused had decreased level of a GR protein. This shows that events later in life (such as those leading to a suicide) do not actually alter genetic makeup, rather, it is the early childhood interactions which cause epigenetic changes leading to adult behavior. These data are consistant with those of the rats and show the importance and effect of having proper nurture as a child.
But in reality, how important is it to be calm and controlled in response to stress? Rats are found in urban areas as well as in the wild.
What were to happen if one of the calm happy rats were to stumble upon a mouse (or, in this case, rat) trap? It would be less concerned about danger and be more likely to die, whereas an anxious rat would be guarded and could better survive the harsh environment.
What is the significance of these epigenetic changes for humans? Maybe living in a developed society has prevented us from realizing just how much nurture plays a role in development. Do those born into a war-ridden society have an inactive GR gene and thus a guarded and anxious personality? This is probably advantageous for survival.
In our society, we will of course never be left alone immediately after birth to fend for ourselves. But, what degree of nurture must we receive in order to grow up to be productive members of society? Why are species like turtles able to survive without a mom? Epigenetic studies will be key in future questions concerning nature and nurture.