Spark: The Revolutionary New Science of Exercise and the Brain

by John J. Ratey

the fight-or-flight response doesn’t exactly fly in the boardroom.

The way you choose to cope with stress can change not only how you feel, but also how it transforms the brain.

if the processed signal from the cortex to the amygdala breaks up, you can’t think and you freeze.

in chronic stress, the action of cortisol amasses a surplus fuel supply around the abdomen in the form of belly fat.

The problem with our inherited stress response is that it mobilizes energy stores that don’t get used.

It seems that, like stress itself, cortisol isn’t simply good or bad. A little bit helps wire in memories; too much suppresses them; and an overload can actually erode the connections between neurons and destroy memories.

if a potential memory comes along during stress, it has a more difficult time recruiting neurons to be part of its own new circuit. It needs to clear a certain threshold to make an impression.

This likely explains why memories not related to the stressor are blocked during the stress response. It also helps explain why constantly high levels of cortisol—due to chronic stress—make it hard to learn new material, and why people who are depressed have trouble learning.

excess cortisol can block access to existing memories,

even if we followed the most demanding governmental recommendations for exercise and logged thirty minutes of physical activity a day, we’d still be at less than half the energy expenditure for which our genes are encoded.

A common protocol scientists use to induce the physiological stress response in rats is to remove them from their social structure; simply isolating them activates stress hormones.

The advantage of using exercise to inoculate the brain against stress is that it ramps up growth factors more than other stimuli do.

Resilience is the buildup of these waste-disposing enzymes, neuroprotective factors, and proteins that prevent the naturally programmed death of cells.

The best way to build them up is by bringing mild stress on yourself: using the brain to learn, restricting calories, exercising, and, as Mattson and your mother would remind you, eating your vegetables.

If mild stress becomes chronic, the unrelenting cascade of cortisol triggers genetic actions that begin to sever synaptic connections and cause dendrites to atrophy and cells to die; eventually, the hippocampus can end up physically shriveled, like a raisin.

When you suffer from chronic stress, you lose the capacity to compare the situation to other memories or to recall that you can grab a jump rope and immediately relieve the stress or that you have friends to talk to or that it’s not the end of the world. Positive and realistic thoughts become less accessible, and eventually brain chemistry can shift toward anxiety or depression.

Exercise increases the efficiency of intercellular energy production, allowing neurons to meet fuel demands without increasing toxic oxidative stress.

Taken all together, these factors combine forces to make the brain bloom and prevent the damaging effects of chronic stress from taking hold. In addition to cranking up the cellular repair mechanisms, they also keep cortisol in check and increase the levels of our regulatory neurotransmitters serotonin, norepinephrine, and dopamine.

When you say you feel less stressed out after you go for a swim, or even a fast walk, you are.

Chronic stress is linked to some of our most deadly diseases. If repeated spikes in blood pressure damage the vessels, plaque can build up at those areas and lead to atherosclerosis.

In neurological terms, fear is the memory of danger.

But nobody really knows whether exercise can entirely replace medication. Our brains are just too complex.

“I just got too busy and forgot the benefits of working out,” she says. “Now I feel like I have my brain back.”

chronic depression may cause structural damage in the thinking brain.

many patients with depression complain of learning and memory trouble,

Now we see depression as a physical alteration of the brain’s emotional circuitry.

In depression, it seems that in certain areas, the brain’s ability to adapt grinds to a halt. The shutdown in depression is a shutdown of learning at the cellular level. Not only is the brain locked into a negative loop of self-hate, but it also loses the flexibility to work its way out of the hole.

Redefining depression as a connectivity issue helps explain the wide range of symptoms people experience. It’s not just a matter of feeling empty, helpless, and hopeless. It affects learning, attention, energy, and motivation—disparate systems that involve different parts of the thinking brain. Depression also affects the body, shutting down the drive to sleep, eat, have sex, and generally look after ourselves on a primitive level.

depression is primarily a communication breakdown, or a loss of the brain’s ability to adapt,

brain-derived neurotrophic factor (BDNF)

learned helplessness, a popular way of describing human depression that implies an inability to cope with adversity and to take the action necessary to survive and flourish.

In postmortem studies of people with depression who died of suicide, their brains had significantly decreased levels of BDNF.

Exercise boosts BDNF at least as much as antidepressants, and sometimes more,

a shutdown of neurogenesis might be a factor in depression.

The key, I think, is to wake up the brain and the body so you can pull yourself out of the downward spiral. What makes aerobic exercise so powerful is that it’s our evolutionary method of generating that spark. It lights a fire on every level of your brain, from stoking up the neurons’ metabolic furnaces to forging the very structures that transmit information from one synapse to the next.

exercise immediately improves the highest form of thinking.

If you have severe depression, you may feel like you’re at the bottom of a pit, in a state of slow death, and that it’s almost impossible to make it outside or go to the gym or even think about moving.

omega-3 supplements, which are proven to have antidepressant effects.

exercise helps regulate the amygdala,

“If I don’t do it, it’s not like I feel guilty,” he says. “It’s that I feel like I’ve missed something in my day, and I want to go do it. Because I figured out that while I’m exercising I don’t have trouble concentrating on anything.”

exercise is the single most powerful tool you have to optimize your brain function—is