What's really going on in PTSD brains? Experts suggest new theory
October 7, 2016
Science Daily/University of Michigan Health System
PTSD experts agree that the condition has its roots in very real, physical processes within the brain – and not some sort of psychological “weakness”. But no clear consensus has emerged about what exactly has gone “wrong” in the brain. A new theory that integrates decades of research focuses on a key function called context processing.
For decades, neuroscientists and physicians have tried to get to the bottom of the age-old mystery of post-traumatic stress disorder, to explain why only some people are vulnerable and why they experience so many symptoms and so much disability.
All experts in the field now agree that PTSD indeed has its roots in very real, physical processes within the brain -- and not in some sort of psychological "weakness." But no clear consensus has emerged about what exactly has gone "wrong" in the brain.
In a Perspective article published this week in Neuron, a pair of University of Michigan Medical School professors -- who have studied PTSD from many angles for many years -- put forth a theory of PTSD that draws from and integrates decades of prior research. They hope to stimulate interest in the theory and invite others in the field to test it.
The bottom line, they say, is that people with PTSD appear to suffer from disrupted context processing. That's a core brain function that allows people and animals to recognize that a particular stimulus may require different responses depending on the context in which it is encountered. It's what allows us to call upon the "right" emotional or physical response to the current encounter.
A simple example, they write, is recognizing that a mountain lion seen in the zoo does not require a fear or "flight" response, while the same lion unexpectedly encountered in the backyard probably does.
For someone with PTSD, a stimulus associated with the trauma they previously experienced -- such as a loud noise or a particular smell -- triggers a fear response even when the context is very safe. That's why they react even if the noise came from the front door being slammed, or the smell comes from dinner being accidentally burned on the stove.
Context processing involves a brain region called the hippocampus, and its connections to two other regions called the prefrontal cortex and the amygdala. Research has shown that activity in these brain areas is disrupted in PTSD patients. The U-M team thinks their theory can unify wide-ranging evidence by showing how a disruption in this circuit can interfere with context processing and can explain most of the symptoms and much of the biology of PTSD.
"We hope to put some order to all the information that's been gathered about PTSD from studies of human patients, and of animal models of the condition," says Israel Liberzon, M.D., a professor of psychiatry at U-M and a researcher at the VA Ann Arbor Healthcare System who also treats veterans with PTSD. "We hope to create a testable hypothesis, which isn't as common in mental health research as it should be. If this hypothesis proves true, maybe we can unravel some of the underlying pathophysiological processes, and offer better treatments."
Liberzon and his colleague, James Abelson, M.D., Ph.D., describe in their piece models of PTSD that have emerged in recent years, and lay out the evidence for each. The problem, they say, is that none of these models sufficiently explains the various symptoms seen in patients, nor all of the complex neurobiological changes seen in PTSD and in animal models of this disorder.
The first model, abnormal fear learning, is rooted in the amygdala -- the brain's 'fight or flight' center that focuses on response to threats or safe environments. This model emerged from work on fear conditioning, fear extinction and fear generalization.
The second, exaggerated threat detection, is rooted in the brain regions that figure out what signals from the environment are "salient," or important to take note of and react to. This model focuses on vigilance and disproportionate responses to perceived threats.
The third, involving executive function and regulation of emotions, is mainly rooted in the prefrontal cortex -- the brain's center for keeping emotions in check and planning or switching between tasks.
By focusing only on the evidence bolstering one of these theories, researchers may be "searching under the streetlight," says Liberzon. "But if we look at all of it in the light of context processing disruption, we can explain why different teams have seen different things. They're not mutually exclusive."
The main thing, says Liberzon, is that "context is not only information about your surroundings -- it's pulling out the correct emotion and memories for the context you are in."
A deficit in context processing would lead PTSD patients to feel "unmoored" from the world around them, unable to shape their responses to fit their current contexts. Instead, their brains would impose an "internalized context" -- one that always expects danger -- on every situation.
This type of deficit, arising in the brain from a combination of genetics and life experiences, may create vulnerability to PTSD in the first place, they say. After trauma, this would generate symptoms of hypervigilance, sleeplessness, intrusive thoughts and dreams, and inappropriate emotional and physical outbursts.
Liberzon and Abelson think that testing the context processing theory will enhance understanding of PTSD, even if all of its details are not verified. They hope the PTSD community will help them pursue the needed research, in PTSD patients and in animal models. They put forth specific ideas in the Neuron paper to encourage that, and are embarking on such research themselves.
The U-M/VA team is currently recruiting people with PTSD -- whether veterans or not -- for studies involving brain imaging and other tests.
In the meantime, they note that there is a growing set of therapeutic tools that can help patients with PTSD, such as cognitive behavioral therapy mindfulness training and pharmacological approaches. These may work by helping to anchor PTSD patients in their current environment, and may prove more effective as researchers learn how to specifically strengthen context processing capacities in the brain.
https://www.sciencedaily.com/releases/2016/10/161007123407.htm
Mindfulness meditation training changes brain structure in eight weeks
January 21, 2011
Science Daily/Massachusetts General Hospital
Participating in an 8-week mindfulness meditation program appears to make measurable changes in brain regions associated with memory, sense of self, empathy and stress. A new study is the first to document meditation-produced changes over time in the brain's gray matter.
"Although the practice of meditation is associated with a sense of peacefulness and physical relaxation, practitioners have long claimed that meditation also provides cognitive and psychological benefits that persist throughout the day," says Sara Lazar, PhD, of the MGH Psychiatric Neuroimaging Research Program, the study's senior author. "This study demonstrates that changes in brain structure may underlie some of these reported improvements and that people are not just feeling better because they are spending time relaxing."
Previous studies from Lazar's group and others found structural differences between the brains of experienced mediation practitioners and individuals with no history of meditation, observing thickening of the cerebral cortex in areas associated with attention and emotional integration. But those investigations could not document that those differences were actually produced by meditation.
"It is fascinating to see the brain's plasticity and that, by practicing meditation, we can play an active role in changing the brain and can increase our well-being and quality of life." says Britta Hölzel, PhD, first author of the paper and a research fellow at MGH and Giessen University in Germany. "Other studies in different patient populations have shown that meditation can make significant improvements in a variety of symptoms, and we are now investigating the underlying mechanisms in the brain that facilitate this change."
Amishi Jha, PhD, a University of Miami neuroscientist who investigates mindfulness-training's effects on individuals in high-stress situations, says, "These results shed light on the mechanisms of action of mindfulness-based training. They demonstrate that the first-person experience of stress can not only be reduced with an 8-week mindfulness training program but that this experiential change corresponds with structural changes in the amygdala, a finding that opens doors to many possibilities for further research on MBSR's potential to protect against stress-related disorders, such as post-traumatic stress disorder." Jha was not one of the study investigators.
http://www.sciencedaily.com/releases/2011/01/110121144007.htm
Mindfulness training for military could help them deal with stress
May 16, 2014
Science Daily/University of California - San Diego
Mindfulness training -- a combination of meditation and body awareness exercises -- can help U.S. Marine Corps personnel prepare for and recover from stressful combat situations. The study suggests that incorporating meditative practices into pre-deployment training might be a way to help the U.S. military reduce rising rates of stress-related health conditions, including PTSD, depression and anxiety, within its ranks.
The study, published in the May 16, 2014 online issue of the American Journal of Psychiatry, suggests that incorporating meditative practices into pre-deployment training might be a way to help the U.S. military reduce rising rates of stress-related health conditions, including PTSD, depression and anxiety, within its ranks.
"Mindfulness training won't make combat easier," said Martin Paulus, MD, professor of psychiatry and senior author. "But we think it can help Marines recover from stress and return to baseline functioning more quickly."
Drawing on the teachings of Zen Buddhism, scientists describe mindfulnes as a mental state characterized by "full attention to the present moment without elaboration, judgment or emotional reactivity." Mindfulness training, traditionally practiced through sitting meditation, attempts to cultivate this mental state by quieting the mind of extraneous thoughts.
In the study, Marine infantrymen in four platoons at Marine Corps Base Camp Pendleton took an eight-week course in mindfulness, tailored for individuals operating in highly stressful environments.
The course included classroom instruction on meditation and homework exercises, as well as training on interoception -- the ability to help the body regulate its overall physical equilibrium (homeostasis) by becoming aware of bodily sensations, such as tightness in the stomach, heart rate and tingling of the skin. "If you become aware of tightness in your stomach, your brain will automatically work to correct that tightness," Paulus explained.
Participating Marines, along with others who had not undergone mindfulness training, then spent a day in mock immersive combat at a 32,000-square-foot training facility staged to resemble a rural Middle Eastern village. During the day's exercises, Marines patrolled the village, met village leadership and responded to a highly realistic ambush.
The scientists found that the heart and breathing rates of those who had received mindfulness training returned to their normal, baseline levels faster than those who had not received the mindfulness training. Blood levels of a tell-tale neuropeptide suggested that the mindfulness-trained Marines experienced improved immune function, as well.
Subsequent magnetic resonance imaging scans revealed that the mindfulness-trained Marines had reduced activity patterns in regions of the brain responsible for integrating emotional reactivity, cognition and interoception. Lori Haase, a postdoctoral fellow in Paulus' lab and a co-author of the study, said similar brain activity patterns had been observed in high performance athletes and Navy seals. High-activity levels in these areas of the brain, she noted, are associated with anxiety and mood disorders. The scientists hypothesize that reduced brain activity in the anterior insula and anterior cingulate may be characteristic of elite performers in general.
"That we can re-regulate the activity in these areas with so little training is this study's most significant finding," Paulus said. "Mindfulness helps the body optimize its response to stress by helping the body interpret stressful events as bodily sensations. The brain adds less emotional affect to experiences and this helps with stress recovery."
:http://www.sciencedaily.com/releases/2014/05/140516092519.htm