flow, enhance mental acuity, and intimidate our peers.
Interestingly, extreme temperatures are another type of
physical stressor that can induce effects similar to exercise.
One study found that when men stayed in a sauna that was
heated to 80°C (176°F) until subjective exhaustion, their
levels of norepinephrine increased threefold.^31 (A study in
women saw a similar but smaller boost.)^32 Cold water
immersion is another massive neurological modulator and
has been used by various cultures for centuries as a health-
boosting tool. Anyone feeling mentally fatigued need only
take a cold shower or have a dip in an ice bath to reap the
mental benefits—the surge of norepinephrine from a cold
shock, reported to increase over fivefold in humans, can
make the brain feel like it’s coming back “online.”^33 It’s
perhaps not a coincidence that a major Russian holiday that
involves plunging into freezing lakes through holes cut in
the ice is called Epiphany!
Aside from its well-documented role in focus, attention,
and memory formation, some other very interesting aspects
of norepinephrine have emerged from the literature.
Increasing norepinephrine in animals boosted their
resilience to stress, enhancing their capacity to rebound
from traumatic events.^34 Norepinephrine also has an anti-
inflammatory effect in the brain, and stimulating the
neurotransmitter may strengthen a brain region that tends to
be implicated early in the development of Alzheimer’s