← Spark The Revolutionary New Science of Exercise and the Brain
Spark Chapter 6. Attention Deficit
Author: John J. Haley, Eric Hagerman Publisher: New York, NY: Little Brown Spark. Publish Date: 2008 Review Date: 2023-5-4 Status:📚
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The cerebellum is a primitive part of the brain that for decades was assumed to be involved only with governing and refining movement. When we learn how to do something physical, whether it’s a karate kick or snapping our fingers, the cerebellum is hard at work. The cerebellum takes up just 10 percent of the brain’s volume, but it contains half of our neurons, which means it’s a densely packed area constantly buzzing with activity. But it keeps rhythm for more than just motor movements: it regulates certain brain systems so they run smoothly, updating and managing the flow of information to keep it moving seamlessly. In patients with ADHD, parts of the cerebellum are smaller in volume and don’t function properly, so it makes sense that this could cause disjointed attention.
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The cerebellum sends information to the prefrontal and motor cortices — the centers for thinking and movement — but along the route is an important cluster of nerve cells called the basal ganglia, which acts as a sort of automatic transmission, subconsciously shifting attentional resources as the cortex demands. It’s modulated by dopamine signals stemming from the substantia nigra. Dopamine works like transmission fluid: if there’s not enough, as is the case in people with ADHD, attention can’t easily be shifted or can only be shifted all the way into high gear.
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A lot of what scientists know about the basal ganglia comes from research into Parkinson’s disease, which is caused by a depletion of dopamine in this area. The disease wreaks havoc with a patient’s ability to coordinate not only motor movements but also complex cognitive tasks. In the early stages of Parkinson’s, these malfunctions show up as adult-onset ADHD.
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The parallel is important because, based on a number of strong studies, neurologists are now recommending daily exercise in the early stages of Parkinson’s disease to stave off symptoms. Scientists induced Parkinson’s in rats by killing the dopamine cells in their basal ganglia, and then forced half of them to run on a treadmill twice a day in the ten days following the “onset” of the disease. Incredibly, the runners’ dopamine levels stayed within normal ranges and their motor skills didn’t deteriorate. In one study on people with Parkinson’s, intensive activity improved motor ability as well as mood, and the positive effects lasted for at least six weeks after they stopped exercising.
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What I find so compelling is the strong relationship between movement and attention. They share overlapping pathways, which is probably why activities like martial arts work well for ADHD kids — they have to pay attention while learning new movements, which engages and trains both systems.
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A controversial treatment for dyslexia — which occurs in about 30 percent of ADHD patients — relies entirely on physical movements to train the cerebellum. Dyslexia, dyspraxia, and attention treatment (DDAT) is based on the theory that a disruption in the brain’s ability to coordinate movement might be responsible for eye-tracking problems and thus difficulties in learning to read and write. Researchers also know that most children with dyslexia perform worse than average on tests of cerebellar function. DDAT involves practicing a collection of fairly simple motor-skills drills twice a day for ten minutes. In 2003 British researchers tested the effectiveness of DDAT on thirty-five children with dyslexia and declared the results “astounding.” Compared to no treatment, the students who followed the DDAT regimen for six months showed a significant improvement in reading and writing fluency, eye movement, cognitive skills, and physical measures such as dexterity and balance.
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My friend and colleague Ned Hallowell uses this method (among many others) at his ADHD treatment center and has seen the positive effects in his own son. And prominent scientists at Columbia University College of Physicians and Surgeons are just embarking on a large study assessing the usefulness of the DDAT method as a treatment for ADHD.
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Pharmacological studies have shown that ADHD drugs help normalize the activity of the cerebellum, as well as the corpus striatum, so it’s clear these areas are important to attention as well as movement. Perhaps by training our brain’s movement centers to improve its higher functions, we can bring about a day when we’re not as dependent on medication.
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The first paper I wrote on adult ADHD was soundly rejected, based on the criticism that I must be misdiagnosing some form of underlying depression or anxiety or that I was trying to introduce a new disorder.
Note: We’ve reified these disorders and treat them as if they’re completely different phenomena, but they overlap, which is probably is because they involve the same neural mechanisms
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School is an excruciating environment for a child with ADHD, given the need to sit still, face forward, and listen intently to a teacher for the better part of an hour.
Note: Nobody enjoys doing this! Not just people “with” ADHD
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In the brain stem, balancing norepinephrine in the arousal center also helps. “Chronic exercise improves the tone of the locus coeruleus,” says Amelia Russo-Neustadt, a neuroscientist and psychiatrist at California State University. The result is that we’re less prone to startle or to react out of proportion to any given situation. And we feel less irritable.
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An overactive cerebellum also contributes to fidgetiness in ADHD kids, and recent studies have shown that ADHD drugs that elevate dopamine and norepinephrine bring this area back in balance. Exercise also increases norepinephrine.
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The seminal 2006 study from Arthur Kramer of the University of Illinois used MRI scans to show that walking as few as three days a week for six months increased the volume of the prefrontal cortex in older adults. And when he tested aspects of their executive function, they showed improvement in working memory, smoothly switching between tasks and screening out irrelevant stimuli. Kramer wasn’t on the trail of ADHD, but his findings illustrate another way exercise might help.
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Everyone agrees that exercise boosts levels of dopamine and norepinephrine. And one of the intracellular effects of these neurotransmitters, according to Yale University neurobiologist Amy Arnsten, is an improvement in the prefrontal cortex’s signal-to-noise ratio. She has found that norepinephrine boosts the signal quality of synaptic transmission, while dopamine decreases the noise, or static of undirected neuron chatter, by preventing the receiving cell from processing irrelevant signals.