On Gut-Brain connection - Neuroscientists David Levingthal and Peter Strick proposed that nerve cells in the deep brain influence the stomach. They studied the pathways that modulate gut function and found that the rostal insula and medial prefrontal cortex, regions associated with interoception and emotional control, actually had nerves feeding from the stomach and back to it, creating a loop of communication between brain and gut.
Even now, there are physicians that tell patients that their thoughts are not important when eating. They will encourage multi-tasking and eating on the go. The holistic adage, You Are What You Eat is considered pseudoscience, and the idea that your negative words or watching a lecture while eating can affect digestion is considered ludicrous.
Then an article appears in PNAS! As one of the world's most prestigious journals, which earns respect for each person who publishes in it, PNAS, the Proceedings of the National (USA) Academy of Sciences, published a study by neuroscientists David Levingthal and Peter Strick at the University of Pittsburgh. They proposed that nerve cells in the deep brain influence the stomach. They studied the pathways that modulate gut function and found that the rostal insula and medial prefrontal cortex, regions associated with interoception and emotional control, actually had nerves feeding from the stomach and back to it, creating a loop of communication between Gut-Brain.
Interoception is the body's awareness of sensations in the internal state of the body that we normally cannot control. This type of internal perception allows us to experience many body sensations such as a growling stomach, racing heart, a dry mouth, or tense muscles, that may signal something that the person needs to address such as eating a meal, or relaxing or eating some grapes to lower thirst and lubricate the mouth.
Ayurveda has been teaching this concept of the Gut-Brain connection for 5000 years, and integrative physicians talk about The Second Brain, and Gut Instinct. Ayurveda says that 80% of all diseases begin in the Gut-Brain.
"In general, parasympathetic output [“rest and digest,” involving internal, vegetative processes] to the stomach tends to increase secretions and enhances the patterns of smooth muscle contractility that are required for processing a meal. In contrast, sympathetic output [“fight or flight,” involving action] to the stomach tends to decrease secretions and inhibit these patterns of smooth muscle contractility. Both sets of outputs alter the microenvironment of the stomach, and thus its microbiome, by controlling the exposure of ingested bacteria to acid, proteolytic enzymes, mucin, and immune factors."
The rostral insula is linked to the stomach by a series of three synapses, or intersections in the heavy congestion highways from brain to the stomach. The rostral insula gathers information coming from the non-voluntary parts of the body, including signals from the stomach and has been viewed as a sensory processing unit for those parts of the body to connect all thinking inputs with the sense of the internal state of the body, a function critical for interoception.
In addition, this study implicates the rostral insula as the part of the brain that connects our so-called gut feelings up to the brain and back down to the gut to implement what our instinct told us. This can sometimes be a signal to stop eating, or to eat faster.
An additional source of control connects the medial prefrontal cortex of the brain, which regulates numerous cognitive functions, including attention, habit formation, inhibitory control, and types of memory such as working, spatial or long-term memory, to the gut. This connection implies that non-pharmaceutic therapies have positive and long-lasting therapeutic benefits, such as mental and psychological therapies of yoga, shirodhara (oil massage on the head), pranayama (breathwork) and positive habits.
In summary, the study provides a concrete neural basis for the concept that specific areas of the cerebral cortex differentially control stomach function.
Based on the Scientific Review of
Levinthal DJ and Peter L. Stricl PL. Multiple areas of the cerebral cortex influence the stomach, PNAS, June 9, 2020;117(23):13078–13083.
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