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The Size and Connectivity of the Amygdala Predicts Anxiety

A larger amygdala is linked to a higher anxiety risk in children and adults.

In a study released on Nov. 20, 2013, researchers at Stanford University School of Medicine have found that measuring the size and connectivity of the amygdala—a part of the brain associated with processing emotion—can predict the degree of anxiety a young child is experiencing in daily life.

Prolonged stress and anxiety during childhood increase the risk of someone developing anxiety disorders and depression later in life. In the breakthrough study, the researchers at Stanford found that the larger the amygdala—and the stronger its connections with other regions of the brain responsible for perception and the regulation of emotion—the greater the amount of anxiety a child was experiencing. This study was published online in Biological Psychiatry.

A Larger Amygdala Can Equate to Higher Anxiety in Childhood

The amygdala is an evolutionarily primitive part of the brain located deep in the temporal lobe. It comprises several subregions associated with different aspects of perceiving, learning, and regulating emotions. Studies of laboratory animals placed in an environment causing chronic stress have determined that the animals' amygdalae grew additional synapses and that this synaptic connectivity resulted in chronic anxiety.

The Stanford researchers acknowledge that some anxiety is an important emotional and biological reaction to both "eustress" (good stress) and "distress" (bad stress) at all stages of life. However, sustained anxiety can lead to disabling conditions such as phobia, post-traumatic stress disorder (PTSD) and generalized anxiety disorder. Studies of adults suffering from anxiety disorders have shown that they also possess enlarged, highly connected amygdalae.

The basolateral amygdala is the specific region that was larger in children with higher anxiety. This is an evolutionarily older and "primal" subregion that processes emotion-related sensory information and communicates it to the more cerebral neocortex which is an evolutionarily newer part of the brain according to Shaozheng Qin, Ph.D., the lead author of the study.

Qin used magnetic resonance imaging to measure the size of the various subregions of the amygdala and functional MRI to measure the connectivity of those regions to other areas of the brain. "The basolateral amygdala had stronger functional connections with multiple areas of the neocortex in children with higher anxiety levels," Qin said.

The Stanford researchers have “identified four functional neocortical systems that were affected. One of the systems deals with perception, another with attention and vigilance, a third with reward and motivation, and the fourth with detection of salient emotional stimuli and regulation of emotional responses. All four of these core systems are impacted by childhood anxiety," Qin said.

The researchers emphasize that “these findings do not mean that every young child with an enlarged and highly connected amygdala will necessarily go on to develop a mood disorder,” said Vinod Menon, Ph.D., professor of psychiatry and behavioral sciences and senior author of the study. "We are not at a point where we can use these findings to predict the likelihood of a child developing mood and anxiety disorders as an adult, but it is an important step in the identification of young children at risk for clinical anxiety," Menon said.

Menon added that they were surprised that alterations to the structure and connectivity of the amygdala were so significant in the children with higher levels of anxiety, given both the young age of the children and the fact that their anxiety levels were still too low to be considered clinical.

Participants in the study included 76 children ranging in ages 7 to 9. "For the cognitive emotional assessments to be reliable, 7 years old is about as young as a child can be," said Menon. "But the changes to the amygdala may have started earlier."

The parents of the children in the study filled out the Childhood Behavior Checklist, a standard measure of a child's general cognitive, social and emotional well-being. All the children in the study were typically developing, with no history of neurological or psychiatric disorders, and were not using medication. None of the children in the study were experiencing so much anxiety in their daily lives that they could be considered clinically anxious.

Menon concludes, “The study provides important new insights into the developmental origins of anxiety. Understanding the influence of childhood anxiety on specific amygdala circuits, as identified in the study, could aid in the early identification and treatment of children at risk for anxiety disorders.”

What Is the Link Between Synesthesia and Autism?

Interestingly, another study about neuroplasticity and the importance of "Neural Darwinism” (the pruning of certain neural connections as part of healthy development) was released on November 19, 2013 by researchers at Cambridge University who found a direct link between synesthesia and autism.

Synesthesia (also spelled synaesthesia) involves people experiencing a 'mixing of the senses.' For example, someone would see colors when they hear sounds, link specific letters to colors, or report that musical notes evoke different tastes. People diagnosed with Autism Spectrum Disorder (ASD) often struggle with social relationships and communication, and tend to have unusually narrow interests and be resistant to change. Both of these conditions result from atypical connections between brain areas that are not usually wired together.

In synesthesia, this means that a sensation in one sensory channel triggers a perception in another channel. Researchers believe that ASD may also be related to atypical brain wiring that creates an over-connectivity of certain neurons which causes the person to hyper-focus on small details while finding it difficult to keep the big picture in mind.

This new study, published in the journal Molecular Autism, found that people with autism are more likely to also have synesthesia. The Cambridge University scientists found that whereas synesthesia usually occurs in 7.2% of the general population, it occurred in 18.9% of people with autism spectrum disorders.

The scientists had a hunch that autism and synesthesia were both related to neural over-connectivity, and therefore that synesthesia might be disproportionately common in autism. They tested for this and found their hypothesis to be correct.

Professor Baron-Cohen said: "I have studied both autism and synaesthesia for over 25 years and I had assumed that one had nothing to do with the other. These findings will re-focus research to examine common factors that drive brain development in these traditionally very separate conditions. An example is the mechanism "apoptosis," the natural pruning that occurs in early development, where we are programmed to lose many of our infant neural connections. In both autism and synaesthesia apoptosis may not occur at the same rate, so that these connections are retained beyond infancy."

Professor Simon Fisher, a member of the team, and Director of the Language and Genetics Department at Nijmegen's Max Planck Institute, added: "Genes play a substantial role in autism and scientists have begun to pinpoint some of the individual genes involved. Synaesthesia is also thought to be strongly genetic, but the specific genes underlying this are still unknown. This new research gives us an exciting new lead, encouraging us to search for genes which are shared between these two conditions, and which might play a role in how the brain forms or loses neural connections."

Donielle Johnson, who carried out the study as part of her Master's degree in Cambridge, said: "People with autism report high levels of sensory hyper-sensitivity. This new study goes one step further in identifying synaesthesia as a sensory issue that has been overlooked in this population. This has major implications for educators and clinicians designing autism-friendly learning environments."

Conclusion: The Importance of Organic Neural Darwinism

These two new studies show that there is a window of opportunity with toddlers and young children to create daily activities and environments that fortify and nourish the neural networks that will optimize a child’s mental and cognitive well-being. Making efforts to prune brain connections linked to anxiety or ASD and encouraging them to atrophy through daily activities early in a child's life may be a way to treat these conditions without pharmaceuticals. That is one goal of The Athlete's Way.

I write extensively about the role of neural Darwinism in creating an optimal mindset and breaking habits of thinking and behavior in my book The Athlete’s Way. Please follow this link for direct page references and excerpts to read more about neural Darwinism and the importance of pruning neural networks throughout a lifespan.

When people think of neuroplasticity—especially through the lens of positive psychology and improved cognitive function—the focus is often on building stronger neural connections between brain areas. However, it’s equally important that we continually break apart certain neural networks that are linked to negative things like: rumination, catastrophizing, being cynical, compulsive, anxious. These habits of thinking become ingrained at a neural level and must be broken apart.

The neural networks linked to habits of thinking and behavior are like a path through the woods. The more your mind and body travels the same path, the stronger those connections become ingrained. If you don’t allow your mind or body to travel these familiar routes day after day, eventually the path disappears. This is neural Darwinism in action and the function of cognitive behavioral therapy (CBT).

Henry David Thoreau captures this metaphor beautifully in Walden when he writes: “The surface of the earth is soft and impressible by the feet of men; and so with the paths which the mind travels. How worn and dusty, then, must be the highways of the world, how deep the ruts of tradition and conformity!” His conclusion brings up the importance of being a trailblazer and that differences in brain size and structure are what make us unique and should be celebrated. We don't want a society full of cookie-cutter clones.

It is a terrifying prospect to imagine a "Brave New World" dystopia where a parent might take a young child who seems to have anxiety for an fMRI, and after identifying a larger than average amygdala prescribing a medication or a surgical procedure to "fix" the "problem." Again, the researchers from Stanford emphasize that not everyone with a larger amygdala will have high anxiety. The brain is very mysterious and complex and it's important to proceed with caution and use common sense.

When my father was training to be a neurosurgeon, people were still performing lobotomies as a form of “psychosurgery” to correct psychiatric disorders. The practice was extremely disturbing to him, obviously. In a lobotomy, a surgeon cuts or scrapes away most of the connections to the prefrontal cortex, often with an ice pick and chisel placed under the upper eyelid. Clearly this practice had harrowing side-effects.

As neuroscientists in the 21st century begin to understand more about brain connectivity and well-being, I believe that it’s important to focus on lifestyle choices and daily habits as a prescriptive, and not pharmaceuticals. It is possible to nourish brain areas and connections that will maximize someone’s potential and take him or her "north-of-zero" while gently pruning the neural connections that take anyone "south-of-zero" without costly drugs with negative side effects.

Bulking up certain brain areas while shrinking others—and strengthening some neural connections while pruning others—offers a lot of promise for taking someone "north-of-zero." It also offers some potential drawbacks. Every human being's neural tapestry is quirky and unique. There is no "one-size-fits-all" formula for optimizing the size and connectivity of brain regions.

Scientists (as well as writers like myself) should be careful about creating an unintended backlash or stigma associated with what might be misperceived as "shortcomings" or "flaws" in terms of someone's brain volume, symmetry, or connectivity.