Scientists used a vibrating capsule to assess people’s gut sensitivities and understand how the brain interprets these signals

My gut instinct tells me that the approach taken seems to be a little primitive, but the results are interesting!

"Our organs constantly communicate a multitude of complex signals to the brain to keep the body functioning. Scientists have been puzzled by how the brain interprets and controls those signals since interoception, the process of sensing signals from the internal organs, is still poorly understood. In a study published in Nature Communications, researchers from the Laureate Institute for Brain Research (LIBR) reported a novel tool for measuring the gut-brain connection. Such a tool could help researchers identify response patterns in healthy and diseased populations. ..."

From the abstract:

"Understanding the neural processes governing the human gut-brain connection has been challenging due to the inaccessibility of the body’s interior. Here, we investigated neural responses to gastrointestinal sensation using a minimally invasive mechanosensory probe by quantifying brain, stomach, and perceptual responses following the ingestion of a vibrating capsule. Participants successfully perceived capsule stimulation under two vibration conditions (normal and enhanced), as evidenced by above chance accuracy scores. Perceptual accuracy improved significantly during the enhanced relative to normal stimulation, which was associated with faster stimulation detection and reduced reaction time variability. Capsule stimulation induced late neural responses in parieto-occipital electrodes near the midline. Moreover, these ‘gastric evoked potentials’ showed intensity-dependent increases in amplitude and were significantly correlated with perceptual accuracy. Our results replicated in a separate experiment, and abdominal X-ray imaging localized most capsule stimulations to the gastroduodenal segments. Combined with our prior observation that a Bayesian model is capable of estimating computational parameters of gut-brain mechanosensation, these findings highlight a unique form of enterically-focused sensory monitoring within the human brain, with implications for understanding gut feelings and gut-brain interactions in healthy and clinical populations."

Scientists used a vibrating capsule to assess people’s gut sensitivities and understand how the brain interprets these signals.   | The Scientist Magazine® Scientists used a vibrating capsule to assess people’s gut sensitivities and understand how the brain interprets these signals.  

Parieto-occipital ERP indicators of gut mechanosensation in humans (open access)

Fig. 2: Parieto-occipital event-related potential (ERP) indicators of gut sensation during vibratory gut stimulation and their association with perceptual accuracy measures during normal and enhanced stimulation in n = 40 biologically independent samples.

Identifying the Neural Link Between Gut Bacteria and Social Behavior in Mice

Very recommendable! Amazing stuff!

Perhaps this research will one day also lead to better treatments for excessively antisocial or violent humans!

"Research has shown that the communities of bacteria that live in a mouse's gut are essential for the animals to exhibit normal social behavior with other mice. Mice that have been bred to be germ-free, without a gut microbiome, display significant antisocial behaviors, such as avoiding a stranger mouse rather than interacting with it. ...
It had already been shown that, on a chemical level, germ-free mice have significantly higher levels of the hormone corticosterone (the analog of the so-called stress hormone, cortisol, in humans) than mice with healthy microbiomes. The team of researchers, led by former Mazmanian lab postdoctoral scholar Wei-Li Wu, aimed to identify the neurons that were both affected by corticosterone and played a role in social behaviors. ...
"There are a lot of neurons in the body that respond to corticosterone—called glucocorticoid receptor-positive neurons—and we wanted to know which cell populations and brain regions were then responsible for the altered social behaviors in germ-free mice?" ...
To address this, the team conducted fecal transplants from wild-type mice with normal gut microbiota into germ-free mice. These mice then showed decreased corticosterone levels and more normal social behavior. The team then systematically identified a species of bacteria that mediated this improvement, namely Enterococcus faecalis. Germ-free mice that were colonized with E. faecalis showed improved social behaviors and lowered corticosterone levels. The mechanisms through which E. faecalis is able to mediate this improvement will be the subject of future research. ...
This work strengthens the emerging appreciation of the profound effects of the gut-brain connection ..."

"... The gut microbiota contribute to social activity in mice, but the gut–brain connections that regulate this complex behaviour and its underlying neural basis are unclear. Here we show that the microbiome modulates neuronal activity in specific brain regions of male mice to regulate canonical stress responses and social behaviours. Social deviation in germ-free and antibiotic-treated mice is associated with elevated levels of the stress hormone corticosterone, which is primarily produced by activation of the hypothalamus–pituitary–adrenal (HPA) axis. Adrenalectomy, antagonism of glucocorticoid receptors, or pharmacological inhibition of corticosterone synthesis effectively corrects social deficits following microbiome depletion. Genetic ablation of glucocorticoid receptors in specific brain regions or chemogenetic inactivation of neurons in the paraventricular nucleus of the hypothalamus that produce corticotrophin-releasing hormone (CRH) reverse social impairments in antibiotic-treated mice. ..."

Identifying the Neural Link Between Gut Bacteria and Social Behavior in Mice | www.caltech.edu How the gut microbiome affects a specific set of neurons responsible for proper social function in mice. Could the germs that live inside of our bodies be affecting our ability to socialize and make friends? Research conducted in recent decades suggests that the answer—for mice—is yes.

Microbiota regulate social behaviour via stress response neurons in the brain (no public access)

Specific bacteria in the gut prompt mother mice to neglect their pups

Amazing stuff! We still know so little about the multitude of bacteria living in our gut and their effects on behavior and the brain!

"As scientists learn more about the microorganisms that colonize the body—collectively called the microbiota—one area of intense interest is the effect that these microbes can have on the brain. A new study led by Salk Institute scientists has identified a strain of E. coli bacteria that, when living in the guts of female mice, causes them to neglect their offspring. ... 
“To our knowledge, this is the first demonstration that the intestinal microbiota is important for promoting healthy maternal behavior and bonding between mom and offspring in an animal model,” ...
“It adds to the ever-growing evidence that there’s a gut-brain connection, and that microbes are important for regulating the behavior of the host that they’re inhabiting.” ..."

"Maternal behavior is necessary for optimal development and growth of offspring. The intestinal microbiota has emerged as a critical regulator of growth and development in the early postnatal period life. Here, we describe the identification of an intestinal Escherichia coli strain that is pathogenic to the maternal-offspring system during the early postnatal stage of life and results in growth stunting of the offspring. ..."

Specific bacteria in the gut prompt mother mice to neglect their pups - Salk Institute for Biological Studies Salk researchers make unexpected discoveries about how a particular microbe influences animal behavior

Here is the link to the referenced paper:

Microbiota control of maternal behavior regulates early postnatal growth of offspring

A Gut-to-Brain Circuit Drives Sugar Preference and May Explain Sugar Cravings

Recommendable! So it is not a sweet tooth, but a sweet nerve via sensors in the gut? :-) Or why artificial sweeteners have not been very succesful!

"Here we examined the neural basis for sugar preference and demonstrate that a population of neurons in the vagal ganglia and brainstem are activated via the gut–brain axis to create preference for sugar. These neurons are stimulated in response to sugar but not artificial sweeteners, and are activated by direct delivery of sugar to the gut."

"By visualizing brain activity when the rodents consumed sugar versus artificial sweetener or water, the researchers for the first time identified the brain region that responds solely to sugar: the caudal nucleus of the solitary tract (cNST). Found in the brain stem, separate from where mice process taste, the cNST is a hub for information about the state of the body."

One of the research paper's authors happens to be Charles S. Zuker! The German word for sugar is Zucker. What a coincidence!

The gut–brain axis mediates sugar preference (published in Nature 4/15/2020)

A Gut-to-Brain Circuit Drives Sugar Preference and May Explain Sugar Cravings | HHMI.org: The sensation of sweetness starts on the tongue, but sugar molecules also trip sensors in the gut that directly signal the brain. This could explain why artificial sweeteners fail to satisfy the insatiable craving for sugar.