Is There an 'Alarm Clock' in the Brain?…Discovery of the Mechanism Behind Sound Response During Sleep

KAIST-KIST Joint Research Results

Animals, including humans, block most sensory nerves while sleeping. However, they respond to surrounding sounds to react to emergency situations. How is this possible? A domestic research team has uncovered the principle behind it. They confirmed the existence of a neural circuit in the brain that acts as an "alarm clock," waking the sleeper when a sound occurs even during deep sleep.

The Korea Advanced Institute of Science and Technology (KAIST) announced on the 20th that Professor Kim Daesu's research team from the Department of Biological Sciences, in collaboration with Dr. Kim Jeongjin's team from the Korea Institute of Science and Technology (KIST), identified the mechanism by which animals respond to sounds and awaken during sleep.

Sleep is a vital physiological process that reorganizes brain activity and maintains health. Since sensory nerve activity is blocked during sleep, the ability to detect surrounding dangers decreases. However, many animals detect and respond to the approach of predators even while sleeping. Scientists believed that animals alternate between deep and light sleep to prepare for unpredictable dangers.

The research team discovered that even during deep sleep, animals have a neural circuit that responds to sounds. While awake, the auditory thalamus (Medial geniculate thalamus) responds to sounds, but during deep sleep, specifically non-REM sleep, the mediodorsal thalamus responds to sounds and awakens the brain.

The study showed that when rats were in deep sleep, the auditory thalamus neurons were also asleep, but the mediodorsal thalamus neurons were awake and responded immediately when sounds were played. Furthermore, when the mediodorsal thalamus was inhibited, rats did not wake up even when sounds were played, and when the mediodorsal thalamus was stimulated, rats woke up within seconds without any sound.

This is the first study demonstrating that auditory signals can be transmitted through different neural circuits depending on sleep and wake states. It was reported on the 7th in the international journal Current Biology and also attracted attention from the international journal Nature.

Professor Kim explained, “This research enhances understanding of arousal and sensory disorders observed in various brain diseases such as sleep disorders and can be applied in diverse fields, including the development of digital healthcare technologies that can control sensory functions in the future.”

This content was produced with the assistance of AI translation services.