Have you ever lain awake in the middle of the night, your thoughts racing like wild horses that cannot be calmed down? Or perhaps you are utterly exhausted, yet your mind remains unusually alert? This could be due to a malfunction in the “sleep switch” of your brain—the GABA (gamma-aminobutyric acid) system. As the most important inhibitory neurotransmitter in the brain, GABA acts like the “brake” of the nervous system, regulating the intensity and rhythm of neural activity and helping us fall asleep. When GABA’s function is impaired, it can lead to sleep disorders.