Have you heard about Dr. Stephen Porges’ Polyvagal Theory? The theory, already 20 years old, replaces our old notions of how the sympathetic (fight/flight) and parasympathetic nervous systems (rest and recuperation) help to keep us calm, alert and safe. The area covered by Polyvagal Theory is huge. It impacts the way we understand our nervous system, senses, emotions, social self and behaviors. We see diagnoses like autism, sensory modulation disorder, borderline personality and others, in a new light.
Polyvagal Theory claims that the nervous system employs a hierarchy of strategies to both regulate itself and to keep us safe in the face of danger. In fact, it’s all about staying safe.
Our ”highest” level strategy is a mechanism Porges calls social engagement. It is a phenomenal system – connecting the social muscles of the face (eyes, mouth and middle ear) with the heart. You knew that your heart came alive with social interaction, and it’s true! This system is regulated through a myelinated branch of the vagus nerve. In evolutionary terms, this is our most evolved strategy (mammals only) for keeping ourselves safe. We use this all the time to clear up misunderstandings, get help, plead for forgiveness, and so on.
The next mechanism, or strategy, is fight or flight. It’s regulated by the sympathetic nervous system. This system is our fall-back strategy when social engagement isn’t a good fit. (Think of seeing someone sneaking up on you!) Note that freeze is not a part of fight or flight.
Our freeze option is primal and is a remnant of our reptilian past. Freeze is a great strategy for turtles and lizards, but it’s usually a bad idea for humans – think of fainting. Therefore, we typically use it last, when social engagement and fight/flight aren’t going to work for us. But there are good uses for freeze. During severe injury, it shuts us down and turns off our registration of pain. We also make use of it during sex, and it helps women regulate pain and response to pain during labor.
Now these systems appear to work in tandem. The social engagement system puts the brakes on the other (fight, flight, freeze) strategies, thus keeping our heart and body active while we work through a situation. The social engagement system will release the brakes to engage a different response to the environment (i.e. running) if engagement doesn’t help to get us into a safe situation.
What Can Go Wrong
We want our nervous system to operate using the social exchange most of the time. It is our most evolved way of being. It is restful and healthy because it allows our gut and other organs to do their job uninterrupted.
However, some of us are programmed from an early age to work from a fight/flight mode. Think of people who are sensory sensitive and recoil from sound, touch, smell or taste. Think of people with autism (in this case, the face to heart connection is not working). Think of people with borderline personality, depression and perhaps other disorders, too. When we are not able to work from our social engagement strategy, then we revert to a modified fight/flight strategy, which puts us in high alert. If we use too much of the fight/flight or freeze strategies, we may end up with gut issues because the gut comes to a halt and we stop digesting food during fight/flight activation.
The Polyvagal Theory has gained great acceptance over the years as pieces of it are shown to hold under laboratory findings. From a psychological viewpoint, it provides us with a rich understanding of self-regulation in the body. From a sensory processing viewpoint, it informs our understanding of sensory modulation.
If you are unfamiliar with the topic, check out the many articles on Dr.Porges’ website. The most comprehensive article is The Polyvagal Perspective, and it is published here on the NIH Public Access site. It contains the physiological underpinnings of the theory as well as perspectives on development, emotions, trauma and many other topics. There is a short video of it here.
Two researchers looked at a biological marker of the social exchange system, RSA, in typical children and in children with sensory modulation issues. RSA is the measure of high-frequency fluctuation in the heart between heart beats. It is a window into the social exchange system. The researchers found that children with sensory modulation issues have a lower level of RSA than their peers, meaning that these children are better prepared to put the breaks on social strategies and instead use fight-or-flight strategies.
As part of the study, the children were (each in turn) given a sensory challenge. The chairs they were seated on tilted backwards unexpectedly. The level of RSA was monitored in each child throughout the incident. The RSA of typical children dropped quickly and then stayed low for a short time. The children with poor sensory modulation skills had a very brief drop of RSA and a quick rebound to their RSA baseline.
This implies that children with sensory modulation symptoms use different strategies to handle safety-related situations than their peers. At this time, it is harder to draw greater conclusions since we do not have an easy-access window into the fight/flight system or the freeze system. With time, we’ll get a better understanding of this. The article can be found here.
Perhaps the most interesting new work making use of the Polyvagal Theory is the work of A. D. (Bud) Craig. Mapping our emotions, this is what he found. (Read about it here.)
Emotions arise from feelings in our organs and gut. The feelings are sent via the vagus nerve to the Anterior Insular Cortex (AIC) in the brain. (There’s a lot going on in the vagus nerve – think of it as a cable with lots of separate wires.) The AIC captures feelings over time and stores them as snapshots of feelings. This is our working emotional memory. These feelings are massaged and integrated with the social exchange to give us both an emotional response to the world around us as well as a safety-driven strategy.
Think of this: I am relaxing in a lounge chair on the beach. I feel safe. Suddenly, a beach ball hits me. My fight or flight instinct kicks it and the sympathetic nervous system stops everything that’s happening (i.e. digestion) in my organs and gut. The gut passes the feeling of stoppage as “alarm” to the brain. This translates in the brain to fear and my body is set in motion. I quickly turn and see it’s a ball and that a child is nearby and smiling at me. My social engagement strategy puts the breaks on my fight/flight response and also calms my heart. I smile at the child. This sends a sense of relief to my gut and it in turn sends a “warm” feeling to the AIC. My heart is still pounding from the surprise, but my response is guided by compassion.
In the above scenario, we specifically looked at a situation with a challenge to safety. But in fact, we spend much of our time worrying about safety. Unless I am completely safe, listening to quiet music in a locked room, I will most likely have safety challenges to respond to. The challenge may be from the scary book I am reading, or from the sense of anxiety I feel when I drop a spoon on the floor. Almost any activity will involve the combined interaction of the various strategies. The bottom line: we are constantly adjusting ourselves to meet the world. Polyvagal Theory gives us a look at how this works.
This is pretty complex stuff – and the theory is still in flux. It changes with each new study that looks at the implications of Polyvagal Theory on our response to the world. It is going to impact research greatly in the months and years ahead. As I mentioned at the beginning, Polyvagal Theory adds a new dimension to how we see autism, sensory issues and other disorders and will, I think, inform our interventions for those disorders in a big way.
What you think is going on in your head may be caused in part by what’s happening in your gut.
A growing body of research shows the gut affects bodily functions far beyond digestion. Studies have shown intriguing links from the gut’s health to bone formation, learning and memory and even conditions including Parkinson’s disease. Recent research found disruptions to the stomach or intestinal bacteria can prompt depression and anxiety—at least in lab rats.
Better understanding the communication between the gut and the brain could help reveal the causes of and treatments for a range of ailments, and provide diagnostic clues for doctors.
The gut—considered as a single digestive organ that includes the esophagus, stomach and intestines—has its own nervous system that allows it to operate independently from the brain.
This enteric nervous system is known among researchers as the “gut brain.” It controls organs including the pancreas and gall bladder via nerve connections. Hormones and neurotransmitters generated in the gut interact with organs such as the lungs and heart.
Like the brain and spinal cord, the gut is filled with nerve cells. The small intestine alone has 100 million neurons, roughly equal to the amount found in the spinal cord, says Michael Gershon, a professor at Columbia University.
The vagus nerve, which stretches down from the brainstem, is the main conduit between the brain and gut. But the gut doesn’t just take orders from the brain.
“The brain is a CEO that doesn’t like to micromanage,” says Dr. Gershon. The brain receives much more information from the gut than it sends down, he adds.
Many people with psychiatric and brain conditions also report gastrointestinal issues. New research indicates problems in the gut may cause problems in the brain, just as a mental ailment, such as anxiety, can upset the stomach.
Stanford’s Dr. Pasricha and colleagues examined this question in the lab by irritating the stomachs of newborn rats. By the time the animals were eight to 10 weeks old, the physical disturbance had healed, but these animals displayed more depressed and anxious behaviors, such as giving up more quickly in a swimming task, than rats whose stomachs weren’t irritated.
Compared to controls, the rats also showed increased sensitivity to stress and produced more of a stress hormone, in a study published in May in a Public Library of Science journal, PLoS One.
Other work, such as that of researchers from McMaster University in Hamilton, Ontario, demonstrated that bacteria in the gut—known as gut flora—play a role in how the body responds to stress. The exact mechanism is unknown, but certain bacteria are thought to facilitate important interactions between the gut and the brain.
Electrically stimulating the vagus nerve has been shown to reduce the symptoms of epilepsy and depression. (One treatment approved by the Food and Drug Administration, made by Cyberonics Inc., is already on the market.)
Exactly why such stimulation works isn’t known, experts say, but a similar procedure has been shown in animal studies to help improve learning and memory.
Earlier this month, researchers made a small step toward understanding a gastrointestinal ailment that typically affects children with autism.
In a study of 23 autistic children and nine typically developing kids, a bacterium unique to the intestines of those with autism called Sutterella was discovered.
The results, published online in the journal mBio by researchers at Columbia’s school of public health, need to be studied further, but suggest Sutterella may be important in understanding the link between autism and digestive ailments, the authors wrote.
Dr. Gershon, professor of pathology and cell biology at Columbia, has been studying how the gut controls its behavior and that of other organs by investigating the neurotransmitter serotonin.
Low serotonin levels in the brain are known to affect mood and sleep. Several common antidepressants work by raising levels of serotonin in the brain.
Yet about 95% of the serotonin in the body is made in the gut, not in the brain, says Dr. Gershon. Serotonin and other neurotransmitters produced by gut neurons help the digestive track push food through the gut.
Work by Dr. Gershon and others has shown that serotonin is necessary for the repair of cells in the liver and lungs, and plays a role in normal heart development and bone-mass accumulation.
Studying the neurons in the gut also may also help shed light on Parkinson’s disease. Some of the damage the disease causes to brain neurons that make the neurotransmitter dopamine also occur in the gut neurons, researchers say.
Researchers are now studying whether gut neurons, which can be sampled through a routine colonoscopy, may help clinicians diagnose and track the disease without invasive brain biopsies, says Pascal Derkinderen, a professor of neurology at Inserm, France’s national institute of health.
Experienced meditators seem to be able switch off areas of the brain associated with daydreaming as well as psychiatric disorders such as autism and schizophrenia, according to a new brain imaging study by Yale researchers.
Meditation’s ability to help people stay focused on the moment has been associated with increased happiness levels, said Judson A. Brewer, assistant professor of psychiatry and lead author of the study published the week of Nov. 21 in the Proceedings of the National Academy of Sciences. He said that understanding how meditation works will aid investigation into a host of diseases. He added:
Meditation has been shown to help in variety of health problems, such as helping people quit smoking, cope with cancer, and even prevent psoriasis.
The Yale team conducted functional magnetic resonance imaging scans on both experienced and novice meditators as they practiced three different meditation techniques.
They found that experienced meditators had decreased activity in areas of the brain called the default mode network, which has been implicated in lapses of attention and disorders such as anxiety, attention deficit and hyperactivity disorder, and even the buildup of beta amyloid plaques in Alzheimer’s disease. The decrease in activity in this network, consisting of the medial prefrontal and posterior cingulate cortex, was seen in experienced meditators regardless of the type of meditation they were doing.
The scans also showed that when the default mode network was active, brain regions associated with self-monitoring and cognitive control were co-activated in experienced meditators but not novices. This might indicate that meditators are constantly monitoring and suppressing the emergence of “me” thoughts, or mind-wandering. In pathological forms, these states are associated with diseases such as autism and schizophrenia.
The meditators did this both during meditation, and also when just resting — not being told to do anything in particular. This may indicate that meditators have developed a “new” default mode in which there is more present-centered awareness, and less “self”-centered, say the researchers. Brewer said:
Meditation’s ability to help people stay in the moment has been part of philosophical and contemplative practices for thousands of years. Conversely, the hallmarks of many forms of mental illness is a preoccupation with one’s own thoughts, a condition meditation seems to affect. This gives us some nice cues as to the neural mechanisms of how it might be working clinically.