Exercise triggers the creation of highly excitable neurons in the hippocampus, the region of the brain associated with memory, learning, and emotional responses. This speeds up overall brain function, but because of the new neurons’ excitability, it should also make the brain more susceptible to anxiety. Yet it doesn’t.
To find out why, the Princeton team split lab mice into two groups. One group had access to a running wheel (with the mice averaging an impressive 2.5 miles per night), and the other did not. After six weeks, the researchers intentionally freaked out all the mice by dunking them in cold water, then looked at their brains with an fMRI machine. Almost immediately, they noticed that the two groups reacted differently. The brain cells of the inactive mice became agitated and leaped into a frenzy, while those of the active mice did not. The reason: the active mice were able to produce and release more of the neurotransmitter GABA, which helps sedate jumpy neurons.
The discovery … marked a breakthrough in understanding how exercise helps the brain regulate anxiety. In essence, exercise creates new, faster neurons, but it also reinforces the physiological mechanism that prevents those uppity brain cells from firing during times of stress.”